Showing papers in "Ecology in 1924"

Ecological Studies of Aquatic Insects: Adaptations of Mayfly Nymphs to Swift Streams

Abstract: This is the first of a proposed series of papers growing out of studies carried on during several summers in the Colorado Rockies, with headquarters at the Summer Mountain Laboratory of the University of Colorado, at Tolland, Gilpin County, Colorado. The authors are much indebted to Francis Ramaley, Director of the laboratory, for materials and equipment, as well as for a stimulating interest in the work. Our studies in that region have dealt with various phases of the ecological relations of the nymphs of stoneflies and mayflies and the larvae of caddisflies, giving special attention to the means by which these insects have met the difficult conditions of life in the swift streams of the region. The Laboratory is located in the valley of South Boulder Creek, at 9,ooo feet, on the east slope of the Front Range of the Rockies, within four miles of the Continental Divide on the west, and about I5 miles from the plains on the east. It has within easy reach a wide range of topographic, climatic and biotic conditions. The creeks and numerous small lakes of the region are of great interest, and are fully described, together with the important topographic and climatic features, in former papers by one of the authors (Dodds, 'I7, '20). The most abundant and striking part of the fauna of the lakes and streams is the insect life, including the immature stages of mayflies, stoneflies, and caddisflies, which here are found in an abundance wholly unknown in ordinary lowland portions of the United States, except in the northern tier of states. We have made special study of the swift streams. It should be clearly recognized that the swift streams of this region are far more than the " babbling brook " or the riffles of streams in level or moderately hilly country, but are in reality often torrential, especially during high water. These streams frequently make a descent of a thousand feet within a distance of a mile, and

Ecological Studies of Aquatic Insects: Size of Respiratory Organs in Relation to Environmental Conditions

Abstract: While making a study of the insect larvae, mayflies, stoneflies and caddisflies of mountain lakes and streams in the Front Range of the Rockies near Tolland, Colorado,2 it was observed that, with very few exceptions, the species living in the lakes and quieter parts of the streams had the respiratory organs larger in proportion to the size of their bodies than the larvae living in the swift streams. It was also noted that there was a tendency for the species living tinder stones in the stream and on pond bottoms with much decaying plant material to have large respiratory organs. These facts seem to be correlated with two things, (i) the oxygen content of the water and (2) the swiftness of the current. With these observations in mind, sudies were made to determine the relationship between the area of the respiratory surface and the body weight for the representative species of the different habitats. I. MAYFLY NYMPHS

The Distribution and Significance of Bacteria in Lake Mendota

Abstract: The purpose of this project was to study the number of bacteria in the water of Lake Mendota at different depths and at different seasons, and to determine some of the factors that influence the number of microorganisms. Special attention has been given to the fluctuation of the number of bacteria and to the factors which influence this fluctuation. Since the chief point in all of this work was the study of the occurrence of bacteria indigenous to the lake, many of the standard methods employed in the examination of water supplies were modified. The point of view for this study is entirely different from that of the student of hygiene, who is concerned primarily with the pathogenic bacteria in water supplies and not with the normal flora of the lake. Harris, in i895, studied the number of bacteria in Lake Mendota at different depths, but failed to find any great difference. In i898 Miss Gordon noted certain of the characteristics of the bacteria of Lake Mendota. Nicholson, i900, reported that the number of bacteria increases with an increase in depth. The maximum number was found at the bottom. Two years later Schorer (I902) studied the longevity of B. typhosms, B. coli and related forms in Lake Mendota water. He found a decrease in number when these organisms were seeded into raw or natural lake water. A review of the investigations of Lake Zurich are of special interest in relation to the work on Lake Mendota. The number, the kind, and the distribution of bacteria in the former have been studied at various times for more than 30 years. Investigations were carried out by Kleiber in i894. The influence of inflowing rivers on the bacteria in lake water was studied. He noted that the zone rich in bacteria due to the entering river water did not extend out in the lake much beyond 20 meters. Pfenniger, I902, reported the results of a study of the bacteria of Lake Zurich. He concluded that the horizontal distribution of bacteria in the lake was generally uniform except for certain periodic fluctuations. The maximum number was found when the lake water was in circulation, and the

Phenology of Entomophilous Flowers

Abstract: The statements made here are based upon observations, from i884 to 19I3, of 470 indigenous and 54 introduced entomophilous flowers. Twentythree more native and seven introduced species, with an average of five days, are excluded as fragmentary. The time of each flower includes early dates for early seasons and late dates for late seasons, and is therefore, when correct, somewhat longer than the actual blooming time observed in a single season. Except the earliest cases, however, it is remarkable how little the blooming times vary. Unless otherwise specified the statements relate to the indigenous species. The groups, except Archichlarnydeae, Syrnpetalae and Campanales, are those given by Bessey (1897, pp. I74-I78), who unites the apetalous and anemophilous groups with their petaliferous and entomophilous relatives, and compares the orders with the paleontological record. This system hardly af fects the families and has little effect on the best known of the dominant suborders. The maximum is the time when the most species are in bloom simultaneously. It is the time of greatest competition between members of a group and may be also the point of origin, the point from which the members tend to diverge. Every natural group has a definite position. It begins at a given time, increases to a maximum point and then declines until all of its members are out of bloom. Their seasons do not coincide, but they overlap. Dyschronous Groups.-A species, genus or family which does not overlap with any of its relatives, or a group which contains species which do not overlap with their relatives, may be called dyschronous. Of 98 genera containing more than one species I4 are dyschronous. They have an average of 2.7 species, while the normal genera average 3.3. Families, being more heterogeneous, would be expected to show more dyschronous cases. Of 58 families 13 are dyschronous. These average 3.7 species while the normal families average 9.2. The general blooming season is determined by the advent of warm weather in the spring and of cold in the fall. The most flowers are in bloom in the most central and warmest month, July, which shows 53.I per cent of the flora, but the maximum is August 20-23 and shows 42.7 per cent. Plants and flowers interfere with one another to such an extent that it is an advantage for them to have their seasons separated as much as possible.

Factors Controlling the Biota of Tide-Pools

Abstract: It is a matter of common observation among workers in marine biology that tide-pools vary greatly in their biota, depending upon their height above low-tide level. In the lower tide-pools there are many plants and animals of the epibenthic zone (the zone from low-tide mark to a depth of 200 metres) which are lacking from tide-pools higher up on the shore. During the seasons of I92i and I922, while at the Atlantic Biological Station, St. Andrews, New Brunswick, I had an opportunity to make a careful study of a series of tide-pools and to obtain data on the factors affecting their biota. The shore in front of the laboratory consists of ledges of sandstone conglomerate, disposed like steps; between these ledges, and in the concavefaces of some of them, are a number of tide-pools. Of these pools I selected six, ranging from near low-tide mark to near high-tide mark, as typical. All are shallow pools, less than four decimetres in depth. The shore on which these tide-pools are located, being on the Bay of Fundy, has the great rise and fall of tide characteristic of that body of water, the amplitude at spring tide being 25 feet and at neap tide about 8 feet less. The pools of this series have their connection with the water of the sea severed when the tide reaches the following levels:

The Influence of Insolation on the Distribution and on the Developmental Sequence of the Flowers of the Giant Cactus of Arizona

Abstract: The Sonoran giant cactus, Carnegiea gigantea, occurs in southern Arizona and in Sonora, Mexico, down to the Yaqui River. It has a huge stem which grows to ten or twelve meters in height and which, just below its first branches, may often have a diameter of 6o or 70 centimeters. The flowers of this cactus occur in a dense crown of from I00 to 200 buds at the tip of the main stem and a similar, but smaller, crown often appears on the tip of each main branch. These flower buds arise along the 20 or 30 ribs of the stem from the areoles, or axillary buds, that were formed during the previous year (or two years). The growing point of the stem of Carnegiea is buried in a dense mass of vhite wool at the bottom of a cup.shaped depression two or three centimeters deep and from five to eight centimeters across. It is only at a distance of a centimeter or two outward from this central growing point that the separate tufts of felted hairs marking the individual areoles become distinguishable. The flower buds of Carnegiea first push through the wool of the areole in early April. About the Desert Laboratory at Tucson flower buds of Carnegiea up to 5 centimeters long were seen on April 29, I915. Opening flowers are to be found from the middle of May, or even earlier in some seasons, till the end of June. These flower buds arise in series of from one or two up to ten, or rarely to as many as fifteen, on each rib of the strongly fluted stem of this cactus. The lowest bud may be 20 or 30 areoles outward from the growing point. The buds of a rib do not arise quite simultaneously. On the contrary, it is evident from the time the flower rudiments first break through the tuft of wool on the areole (in late March or early April) that the buds near the middle of the series on each rib are commonly more advanced. This larger size of the flower buds which lie just over the outer edge of the cuplike end of the stem is evident in figure i, at the right and left above. This relation is not absolute, since there may be smaller buds, or even sterile areoles, between two larger buds (fig. i, y, z). In vigorous crowns from six to eight of the buds of a single rib may mature and bloom. A very striking peculiarity of the arrangement of the flowers of the giant cactus attracted the attention of the writer when in southern Arizona in I9I5.2 1 Botanical Contribution No. 75 from the Johns Hopkins University. 2 This study was initiated during a stay at the Desert Laboratory and was aided by a grant from the Department of Botanical Research, Carnegie Institution of Washington.

Seasonal Migrations of Mackerel in the Black Sea

Abstract: sonal and spawning migrations. In spite of many observations and experiments, our knowledge as to the factors which force fish to migrate and travel many thousands of miles is very incomplete. We expect of course, that the 1'Extracts from manuscript on "The Migrations of Fishes in the Black Sea" presented to the sixth meeting of the Russian Scientific Association in Crimea, in November, [Ecology, Vol. IV, No. 4 (pp. 323-439), was issued Oct. 23, 1923]

Studies in Transpiration of Coniferous Tree Seedlings

Abstract: Adequate studies of transpiration promise to yield much information regarding the water relations of trees. Water consumption in relation to growth, capacity for adjustment in time of water shortage, and ability to obtain moisture from the soil are important questions on which a knowledge of transpiration may be expected to shed light. In i9i9 and I920, transpiration measurements were made at the Southwestern Experiment Station on seedlings of four conifers native to the mountains of Arizona and New Mexico. These species are western yellow pine Pinus scopulorum, Douglas fir Pseudotsuga taxifolia, bristlecone pine Pinus aristata and Engelmann spruce 2' Piceca engelmanni. The vertical arrangement of their natural habitats, beginning with the lowest, is approximately in the order above given. In the zone of yellow pine which ranges between altitudes of 7,0oo and 8,500 feet, the annual precipitation is around 22 inches, and the mean maximum temperature for the growing season is about 75 degrees. Precipitation increases to about 30 inches, while the mean maximum temperatures for the growing season falls to about 6o degrees in the zone of bristlecone pine and Engelmann spruce.

Natural Regeneration of Southern White Cedar

Abstract: Although locally a natural resource of great importance, southern white cedar Chama~ecyparis thyoides has remained one of our least known forest trees Aside from brief studies by Mohr (i899), Pinchot (i899), and Krinbill (19I5), all very limited as to data, little has been done to discover the silvical characteristics of this valuable timber tree of the coastal swamps Consequently when the Appalachian Forest Experiment Station, in cooperation with the State Foresters of Virginia, North Carolina, and New Jersey, initiated a general study 2 during the past year, facts were discovered about southern white cedar that should be of interest to both the silviculturist and the ecologist In this brief preliminary account of these investigations it will be impossible to more than touch upon the high lights A more detailed report will appear at a later date Although the southern white cedar is fastidious in respect to its habitat requirements it has a great variety of associates This variety may be indicated by mentioning only some of the more important examples in different latitudinal parts of its range: in the northern part, as far south as New Jersey, pitch pine Pinus rigida, black gum Nyssa sylvatica, gray birch Betula populifolia and red maple Acer rubrum; in Virginia, North Carolina and South Carolina, pond pine Pinus serotina, red maple, water gum Nyssa biflora, white bay Magnolia glauca and bald cypress Taxodium distichum; in South Carolina, loblolly bay Gordonia lasianthus; in Florida and Alabama, titi Cliftonia monophylla; in Florida, Georgia, Alabama, and Mississippi, water gum, red maple, white bay and slash pine Pinus caribaea Nevertheless, southern white cedar exhibits a strong tendency to grow in pure evenaged stands throughout the greater part of its range A marked characteristic of such stands is a dense tangle of shrubs and vines underneath, which makes passage difficult The hardwood-cypress swamps surrounding the white cedar glades of the Dismal Swamp and Albemarle Sound regions of North Carolina are generally underlain by a clay or sandy clay subsoil In the cedar glades the pro-

The Distribution of the Pale Western Cutworm, Porosagrotis Orthogonia Morr.: A Study in Physical Ecology

Abstract: In a previous study, recently published by the Minnesota Experiment Station, the author (I923) has developed rather briefly the relations between weather factors and the life cycles of certain Noctuidae of the cutworm group, and shown that each species has a definite optimum soil moisture condition during the immature stages, which may be expressed in terms of temperature and precipitation by a characteristic curve. Such curves, which may properly be called " Climograph Curves," as they are based on a modification of the climograph of Ball (i9io), were calculated for three species of Noctuids adapted to rather divergent environments. The climograph itself, a method of plotting which finds varied uses in climatic studies, has been recently discussed in American literature by Varney (I920) and Flanders (1922), to which articles the reader is referred for details. The method as used here is merely the plotting of monthly figures for temperature and precipitation on a graph for which these factors form the axes, connecting the points for successive months by a line showing the direction of the annual cycle. The present paper is a continuation of the earlier study, in which the climograph curve for the Pale Western Cutworm, Porosagrotis orthogonic Morr. (Lepidoptera Noctuidae) was first calculated; and deals with a recalculation of this curve, based on more accurate data, and with the application of the curve to determine the probable limits of the distribution of the species.

Direct Measurement of Water Loss from Vegetation Without Disturbing The Normal Structure of the Soil

Abstract: One of the most serious objections to the usual method of determining the water losses from plants is the almost universal use of containers which are quite too small to accommodate the normal development of the root system But even where containers of sufficient size to overcome this obstacle are employed, the plants are grown in a mass of soil which has been at least fairly recently screened, mixed, aerated and watered and thus its structure is wholly unlike that which occurs in nature This difference has been noticed for a number of years in connection with investigations of root systems of native and crop plants, as well as the markedly better growth of plants in the loose soil of trenches which have been refilled only one to four years Just how long a time is required for such soil to assume the structure and take on the physical and chemical properties of that in an undisturbed area has not been determined, but casual observations indicate that many years are required Undoubtedly the return to the former condition of equilibrium with surrounding soils, and the consequent effect upon the roots of plants, plays no small part in the phenomenon called plant succession, a process often requiring a minimum of I5-25 years for its completion Since a disturbance of the extremely complex system of physical, chemical and biological conditions included in soil structure has such profound effects upon the growth of plants, it seems clear that it might also affect the water relations and thus more or less vitiate attempts to determine the normal transpiration rate by use of containers filled with a soil mixture To obviate these possible errors and to determine the water losses from native and crop plants already grown under normal field conditions without disturbing the root system, the following experiments were performed

The Relation of Nature to Man as Illustrated by the North American Indian

Abstract: According to the reference books of a decade ago, ecology meant for the most part a study of plants and their surroundings. It is not easy to arrive at a full understanding of the then ecological conception for it seems to have carried with it a great deal of the older philosophy from which it sprang. While the early history of the concept is probably lost to us f orever, there are not wanting indications that the ecological idea was conceived in the same atmosphere as the theory of design, or of purposeful adaptation. However that may be, the effort on the part of later professors of ecology has been to eschew all such philosophies except the fundamental assumption that plants and the rest of nature are intricately interdependent one upon the other. The empirical method of science is then appealed to as a technique by which it is hoped that particularistic relations between some plant and some specific aspect of nature may be demonstrated. There is no denying, however, that the true ecologist is hoping for some illuminating laws, or formulations in terms of sequential events, of universal application to plant life and nature. Yet, the tendency seems to have been to seek in some one general aspect of nature the determiners of plant form and distribution, and on the other hand to attempt an enumeration of the associations of other living forms with plants. Yet I am well aware that ecology, as now considered, is not primarily a matter of vegetables, but that one may begin the study of ecology from a zoological horizon. It was suggested, and in fact quite obviously implied, in the invitation tendered me by your society, that someone had gone to such lengths as to extend the ecological conception to men. Yet, whatever may be the real facts, it remains that the history and vicissitudes of anthropology have not been so very different from that of ecology. Ecology, for example, began with plants, but by the very nature of its fundamental assumption,

Correlation between Hydrogen Ion Concentration and Biota of Granite and Limestone Pools

Abstract: Much recent work emphasizes the importance of soil acidity and alkalinity in the distribution of the land flora, but the distribution of aquatic forms in relation to the reaction of the water appears to have received scanty attention. Such recent, and otherwise comprehensive, contributions as those of Hodgetts ('2I)2 and of Pearsall ('22)3 on aquatic ecology do not mention reaction as a factor in distribution. Because of the absence of the complex physical factors concerned in soil problems, together with the greater ease with which analyses may be made, more exact and significant ecological data should be obtainable in an aquatic habitat. Just east of Kingston, Ontario, there is a contact between Algoma granite and Pamelia limestone, with two pools, one in the granite and one in the limestone, within a few hundred yards of each other, which afford an excellent opportunity to study this important question. The data obtained from observations made in I92i and I922 are presented in this preliminary report. The pool in the granite is the site of a quarry abandoned some twenty years ago. This pool is about a quarter of an acre in extent and so situated near the top of a slight elevation that it receives the drainage from only a small area, a considerable part of which is exposed granite rock and the balance granite overlaid by a few inches of soil. There is no other inlet than this drainage from the immediate vicinity. About two thirds of the pond is limited by a perpendicular wall of granite; on one side the rock slopes down gradually, though even this slope has only a few patches of soil. There is no outlet; consequently the depth varies considerably with the season, ranging from I2 and I5 feet to 6 and 8 feet. There are no trees in the vicinity to afford shade, though the south, east and west margins are shaded by the thirty to forty foot perpendicular rocks. The acidity of the water in this pool, as examined at various intervals during two successive seasons, shows a range from pH 6.2 to pH 6.8. This fluctuation is both daily and seasonal. The acidity was highest in the morning and lowest in the evening, evidently resulting from the absorption of 1 Read by title at the Boston meeting of the Ecological Society of America, Dec.,

Amount of Food Eaten by Four Species of Fresh‐Water Fishes

Abstract: Important advances have recently been made in the evaluation of freshwater resources. The planktonts, bottom animals, and plants have been counted, weighed, and analyzed. The rate of propagation and dissolution of the organisms in fresh-water is being studied and some information concerning the rate of " overturn " is thus obtained. It will not be possible to estimate, in a scientific way, the number of animals that each type of environment is capable of supporting until the rate at which each species is consuming materials from the various food resources is known. The present paper relates to one phase of this general problem-describing experiments in which the volume and weight of food consumed per day was determined for four types of fishes: largemouth black bass, pumpkinseed, rock bass, and two species of bullheads. Some observations were also made on long-nosed gars. The fishes used during the experiments, except the gars, were kept in large fruit jars from which the bottoms had been removed. These had a capacity of about i,900 cc. Each end of the jar was covered by a piece of clean cheesecloth held in place by a strong rubber band. The jars were in a covered, metal trough through which water ran continually, and their long axes were parallel to the current so that water ran through them. The watersupply was that of the city of Madison. The temperature of the water varied from I8.70 C. to I9.60 C. The gars would not eat when kept in small wire cages and were fed in a compartment of a covered metal trough which measured i65 cm. long, by 45 cm. wide, and in which flowing water was 20 cm. in depth. At the beginning of each experiment a fresh supply of fishes was secured from Lake Mendota, and all were kept for one day without food before being tested. The length, volume, and weight of each individual was deter-mined before it was placed in a jar. Ten individuals of each species were tested at the same time. During the experiments the food was changed daily, except that it was usually left in the jars over Sunday. A fish was supplied with more of one kind of food than it would be likley to consume during twenty-four hours. Next day a new food was supplied and allowed to remain for about twenty-two hours. Before being placed in a jar with a fish

Relation Between the Downward Penetration of Corn Roots and Water Level in Peat Soil

Abstract: During the season of i920, in connection with research on the University of Wisconsin Marsh, the main results of which have been published,2 opportunity was offered to make some observations on the growth of corn. The tract was part of a peat marsh dyked off from Lake Mendota and under-drained by lines of tiles placed three to five feet below the surface. As the area lay below the lake level, outlet was furnished by means of an electrically operated pump which started and stopped automatically with the rise and fall of water in a large sump pit into which all the drainage lines emptied. Since the land was put under cultivation ensilage corn has always been one of the principal crops. During the growing season it was noticed that there was a great difference in the height of the corn in different parts of the field, even though cultural conditions were absolutely uniform. It was found that the height of the corn appeared to be in a definite relationship to the depth of the water table. This relationship became so marked after the corn had tasseled out that measurements and photographs were made in order, if possible, to determine that relationship under field conditions. For this study a spot was chosen where the water table would remain stationary or nearly so throughout the season. It was in the strip between the dyke and the first tile line. An intercepting ditch 3 feet deep just inside the dyke cut off seepage from the lake. A block in this ditch kept the water at a constant level. The level at the tile line was held constant by the grade of the tile itself. Since the supply of water was from a constant source at the ditch to a constant outlet at the tile, the grade of the water between these points would remain constant, or nearly so, subject only to very slight variations due to rainfall and a somewhat greater variation due to transpiration by the crop. Holes ten feet apart were put down across the strip between the tile line and the ditch, and the actual elevation of the water measured. The resulting levels when plotted gave a curve descending from the ditch to the tile line. Figure i shows the relationship between the water and the ground surface. The elevation of the groundwater having been determined by measure-

Imbibition in Relation to Absorption and Transportation of Water in Plants

Abstract: During the last ten or fifteen years much progress has been made in interpreting the role of imbibition, or colloidal hydration and swelling, in plant life. Formerly associated mainly with the energetic swelling of organic matter, and with certain movements of deformation, such as warping curvatures, twisting of awns and carpellary valves, bursting of capsules, and throwing of seeds and spores, it is now recognized as one of the major influences in organic process. It is important in initiating the germination of seeds, plays a prominent role in the early phases of growth of cells and tissues, apparently bears a relation to the origin of succulence and xeromorphy, is a vitally important factor in the protection of hardy plants from winter injury by freezing, in the hardening of plants to cold, and is probably equally important along with osmotic pressure, as a factor in the absorption, transfer, and distribution of water throughout the body of the plant. A few facts may be presented in regard to each of these functions before proceeding to a detailed discussion of the problems of development of saturation deficit in leaf colloids, the energetics of transfer, and the absorptive functions of

Rainproofing Valves for Atmometers: A Resume

Abstract: The introduction by Livingston of the porous porcelain atmometer into ec. ological instrumentation constituted a service of major importance to physiological ecology. Although minor improvements in the atmometer cups have been made since Livingston summarized the principles of atmometry in I915, no fundamental change has been found necessary. There have, however, been a number of developments in the manner of mounting, especially for field use, and it seems worth while at this time to gather up the main facts in a brief summary. The first use of the atmometer as a field instrument made it evident that some means were necessary to prevent falsification of records by rain. As Livingston has pointed out ('I5), when the outside of the atmometer cup is wetted by rain or heavy dew, the menisci in the pores are destroyed, and added water is drawn into the cup from the outer surface by the force of a water column represented by the height of the top of the cup above the level in the reservoir. To prevent this reversal of direction in the operation of atmometers, mercury valves of various patterns have been constructed. Most of them are based on the principal of a hydrostatic balance; that is, they have placed in the path of the reversing water column a column of mercury considerably greater than the hydrostatic equivalent of the water, thus effectually blocking its flow. Flow in the normal direction is insured by an enlargement in the channel which allows the mercury to collect into a drop and permits the water to pass. Two of the mountings that have been described also added a second mercury valve, virtually an inversion of the first, which permits the return to the exterior of absorbed water but prevents the taking of air into the

Observations on Surface Distribution of Marine Diatoms of Lower California in 1922

Abstract: In July, I922, at the invitation of the Mexican Government, several California scientists joined with Mexican scientists in a biological survey of the Pacific islands in the region of Lower California. The Scripps Institution for Biological Research was represented by Mr. P. S. Barnhart who, while in transit from one place to another, was able to devote a part of his time to collecting microplankton by our standard method.' His efforts resulted in a series of one hundred and fifty-eight catches (each obtained from seven gallons of water), mostly made near the coast of Lower California, but some obtained to seaward between Guadalupe Island and the main shore. Study of these catches was made according to our usual routine for statistical work. The first catches were made on July 9, and the last on August I5. Since some catches were made while south bound and others while north bound, there was, in certain regions, an interval of some days or weeks between the first and last catches. In spite of the fact that such difference in time involves more or less distinct seasonal variations in production, convenience requires that we group the catches on a geographic rather than a time basis in attempting to discuss their significance. For present purposes it has seemed best to designate seven regions, the main localities of which (though not accurately central) are named on the map diagram (Fig. I). Statistical studies were made of both diatoms and dinoflagellates in these catches, but the numbers of dinoflagellates were so small (only in three instances greater than 3,000 per liter) that there is nothing particularly suggestive in their records. For that reason further attention is confined to the diatoms. In the Pt. Banda region catches were made only on the southbound part of the trip July 9-iO. Out of the fifteen catches made at that time only six yielded more than io,ooo diatom cells per liter. One of these was in excess of 80,ooo with Nitzschia serisata Cl. the most prominent form. In the other five large catches Leptocylindrus danicus Cl. was the principal species. In the Cape San Quentin region nineteen catches were taken between Guadalupe Island and the Cape. All of these except the last (taken near the Cape) were very small. The twenty catches taken nearer to the shore south

Reactions of Earthworms to Temperature and Atmospheric Humidity

Abstract: This paper is the record of about one hundred and twenty five experiments carried on at the University of Illinois during I9I5 and i9i6. It was thought that by comparing the reactions of the various species of earthworms some explanation migh be offered for certain peculiarities of distribution and habitat preference exhibited by some of the species. The species used in one or more experiments, when arranged in order relative to soil moisture, driest first, are: (i) Diplocardia comminunis, (2) Lumbricus terrestris, (3) Helodrilus roseus, (4) Helodriliss longicinctus, (5) Helodrilums caliginosus, (6) Helodrilus foetidus, (7) Octolasiuit lacteumn, (8) Helodrilus tetraedrus, and (9) Sparganophilus eiseni (nomenclature after Michaelsen). All specimens were collected in the vicinity of Urbana, most of them within twenty-four hours of the time they were used in experiments. Species five. six and seven were available in abundance at all times, and were used in many experiments. Diplocardia comiiniunis was readily available but was rather unsatisfactory because of its sluggishness and difficulty of locomotion. The four last named species were used in only a few experiments. The apparatus used was devised by Dr. V. E. Shelford ('I4) who suggested the experiments and under whose directions the work was done. It consisted of a cage 45 x 7 x 3 cm. Air entered through a slit in the further side from three fishtail burner shaped chambers, each supplying air to one third of the cage. Double screens separated the slit from the part of the cage in which the animals were confined. The front of the cage was screen. The cage was covered with a glass plate, and during the experiments air flowed slowly across the thirds of the cage, usually at the rate of .oi6 m. per sec. When different humidities or temperatures were introduced they constituted three different humidity conditions with some mixing at the edges. In the majority of experiments the floor of the cage was covered with melted wax into the surface of which, after it had slightly hardened, clean sand was pounded. This gave the cage a hard bottom that prevented burrowing which occurred in loose sand. The sand in the surface of the wax gave sufficient roughness for locomotion. In early experiments the bottom of the cage was covered to a depth of about one half inch with moist sand, closely packed so as to offer a smooth hard surface. Under such conditions

A Note on the Relation of Root Growth in the Soil to the Oxygen Supply: The Growth Ratio

Abstract: In the environment of land plants there are two factors of especial importance aside from the very obvious ones of soil and water. These are the temperature of the soil and the rate of supply of oxygen to the roots. As is known, a variation in temperature, other factors being equal, produces a direct variation in the rate of root growth. Similarly it can be said that a variation in the partial pressure of oxygen in the atmosphere of the soil, provided it is low, produces like results.' It is the aim of the present paper to point out two features in the temperature-oxygen relation of roots, namely, (i) how an increase or a decrease in temperature affects the rate of growth in the presence of a low oxygen partial pressure, and (2) that there is a coincidence between the amount of oxygen necessary to produce certain rates of root growth and the absorption capacity of water for oxygen at the temperatures used. A deficient oxygen supply is a limiting factor in the rate of root growth at any temperature, and to a degree which is characteristic for the temperature and for the species. Under such conditions an expression defining the rate of growth in relation to the temperature and to the supply of oxygen is desirable. For this purpose the growth ratio, or the relative growth as regards the two factors can be conveniently employed. This can be defined as the observed rate of growth at a given temperature and with respect to a given oxygen partial pressure (r) divided by the expected growth rate at the same temperature but under normal aeration relations (R), giving r/R. It has been found that at least to a certain degree the growth ratio may be characteristic of a species, but to what extent this may be the case will require much intensive work, as would be expected. As above defined, the growth ratio appears to have at least two striking characteristics. Under constant conditions of a low oxygen supply its value varies inversely with the temperature. And at constant temperature its value varies directly with the oxygen partial pressure, provided the latter is small.