Showing papers in "American Journal of Botany in 1933"

The decomposition of certain types of forest litter under field conditions

Abstract: Observations in the northern forested regions of America and Europe and at higher elevations in the Southern Appalachians and the Central Alps show that a thick mat of slowly decomposing forest litter is commonly found in closed coniferous stands on the forest floor. It was not until the last few years of the nineteenth century that litter decomposition was given serious study, and even now our knowledge of this problem is in many respects imperfect. More recent results from investigations in microbiological laboratories justify the statement that litter accumulation tends to occur wherever temperature and moisture conditions are such as to retard the activity of microorganisms. The relation of temperature and of moisture as measured by rainfall to the quantitative decomposition of forest litter in pine stands of east-central Ontario, Canada, was studied in 1929 and I930. The results of this investigation are given in this paper. The economic value of information relating to the decomposition of litter is apparent when we consider the problem of forest establishment through natural regeneration. Barr (I929) recognized the necessity for some form of litter treatment prior to seeding, if naturally regenerated spruce seedlings in British Columbia were to survive the first season. Hesselman (I926) made an intensive investigation of litter accumulations in the forests of Sweden. He found that nitrification processes in the soil were very essential for the proper establishment of Scots pine and that certain types of forest litter retarded the activity of nitrifying organisms. Literatture dealing with the influence of temperature on microbial processes has been discussed bv WAaksman (193I, p. 74I-752). It appears that the temperature for optimum development differs for the different organisms. From the point of view of moisture the problem is more complex. But as a broad generalization, excess moisture favors anaerobic activity, whereas the optimum moisture content for aerobic activity is to a large degree dependent upon the coarseness or fineness of the soil medium (Waksman I93I, p. 544, 548). Experimental evidence showing the relative rates of litter decomposition for different coniferous species under natural forest conditions is very inade196

Nuclear divisions in the tapetal cells of certain angiosperms

Abstract: Conflicting statements are to be found in the literature concerning the nature of the nuclear divisions in the tapetal cells of angiosperm pollen sacs. A number of investigators have m-iade casual observations concerning these divisions in the plant witlh whiclh they were working; and in a few instances, notably by Tischler (I905), Bonnet (I9I2), and Mascre and Thomas (I930), detailed studies of the divisions of the tapetal nuclei have been made. The earlier workers reported fragmentation, or amitosis, as the typical method of nuclear division in the cells of the tapetum. Strasburger (I882), reexamining his preparations, found mitotic figures in the tapetal cells and concluded that the appearances formerly described by him as amitosis result from the fact that two daughter nuclei remain attached and finally come to lie in close contact. Tischler (1905) in a study of three species of Ribes reported that the first division of the tapetal nucleus is by mitosis and that any further division is by constriction or fragmentation. Bonnet (I9I2), after critically examining the tapetal cells of ten species of angiosperms, concluded that amitosis does not occur in the nuclei of the tapetal cells and that figures suggesting amitosis are due to mitotic irregularities and nuclear fusions. In one of the plants studied by Bonnet, Datura Stramnonium, O'Neal (I920) reported that the nuclei of the tapetum divide by fragmentation. Mascre and Thomas (I930) agree with Bonnet concerning the absence of amitosis, but find that the tapetal cells may again become uninucleate through nuclear fusions. The presence of typical mitoses in the tapetal cells of Buginivillaea glabra (Cooper, 1931) suggested an examination of other angiosperms with the idea of determining, if possible, the exact nature of these nuclear divisions. Material of 7 mnonocotyledons and 36 dicotyledons, representing in all 24 families, was collected and examined. With the exceptions of the preparations of Pereskia acutleata, which were furnished by Dr. R. I. Evans, and those of Liliunm canadense, Ranunculus fascicularis, Meniispermnum canadense, and Gossypiuns barbadense, which were loaned by Dr. E. L. Fisk, the material for this study was collected in the botanical greenhouses or about the campus of the University of Wisconsin. Flemming's medium solution was used as a

A comparison of osmotic concentrations of supplying and receiving tissues and its bearing on the münch hypothesis of the translocation mechanism

Abstract: Munch (I930) has recently proposed a mechanism which he thinks accounts for the movement of solutes through phloem tissue. In brief, the Munch hypothesis proposes that there is a mass flow of solution from the supplying cells to the receiving cells, that the flow from cell to cell in the phloem passes through the pores of the sieve plates, while for the less specialized supplying or receiving cells the flow is through the more minute plasmodesma. The hypothesis demands that the supplying cells have a higher turgor pressure than the receiving cells. This would mean that, except under rather special conditions, the supplying cells must have a higher osmotic concentration than the receiving cells. There are several points about the hypothesis that are in its favor and make it rather intriguing, but there are also several grave weaknesses involved. No attempt will be made in this paper to summarize these various points, because a rather extensive criticism will be included in a book by the senior author. that is shortly to appear and which deals with many of these and other interesting problems relating to solute translocation in plants. According to the Muinch hypothesis, the supplying cells must have a higher turgor pressure than the receiving cells so that there will be a pressure gradient forcing the solution along the channels leading to the receiving cell. General observations, however, give one the definite impression that receiving tissues are often more turgid than the supplying tissues. For example, the appearance of turgid sprouts developing from increasingly flaccid potato tubers is frequently to be seen, as is also the development of turgid shoots from storage roots, as of carrots, beets and turnips, and from other fleshy storage organs, such as bulbs and corms. The cotyledons of developing seedlings also appear less turgid than the receiving tissues. Quantitative data comparing osmotic concentrations of receiving and supplying tissues are not extensive. The senior author (I920) in experiments incident to translocation studies obtained data indicating an osmotic gradient but with the higher concentrations near the growing tissues which were at the same time the receiving tissues. Fernald (I925) in testing this point presents rather extensive data demonstrating such a reverse gradient leading from

The anatomy of the embryo of cedrus in the dormant stage

Abstract: There are some very interesting anatomical features which beconme differentiated in the embryos of matured conifer seeds. Some differences may be found between the embryos of different genera and families, even though the plan of meristematic organization in the embryo is remarkably uniform throughout the Coniferales. A survey of the literature shows that relatively little which has to do with details in cellular arrangement and organization has been recorded. Most of the investigations have been concerned with the gross external morphologv including size, shape, and number of cotyledons. Schleiden (I3), in his text-book, was among the first who gave a description of tlhe half-grown embryo of a pine and of the embryo in the stage of the matured seed. He reported the order of appearance of the primordia for the organs: root tip, stem tip, and cotyledons. Strasburger (14), the largest single contributor on this subject, corrected Schleiden's error concerning one feature, namely, that it is the plerome apex of the root and not the true root tip which is the first part of the embryo to become differentiated. Schacht (I2) described the meristem of the root tip in a pine and Strasburger gave us more fully the meristematic organization of the root tip and stem tip of various conifers. 1Ie also gave a description of the more mature embryos of Thuja occidentalis, Pinus pnitvilio, Picca vulgaris, Tarus baccata and Ephedra altissima, pointing out the great uniformity in the anatomical structure and organization of the embryo in conifers. His investigations did not include Cedrus which has, at least externally, some striking differences from most of the remaining genera of Abietineae. A few other stages of conifer embryos have occasionally been described such as the descriptions of germinating seedlings by Lord Avebury (ii). In taxonomic monographs and general text-books there are scattered records concerning the size, shape and the number of cotyledons, and occasionally these show sections of seeds or the embryos removed from the seeds. In an extensive series of studies of the vascular anatomy of conifer seedlings, Hill and De Fraine (7) have given a conmprehensive comparison of the seedlings in stages after the early vascular elements are well organized. From these we know the facts concerning the number of cotyledons in a large series of species, with records of the vascular connections in the root and transition region, occurrence and prevalence of fused cotyledons and cotyledonary tubes, divided or fused vascular strands, etc.

Seasonal and diurnal variations in the osmotic values and suction tension values in the aerial portions of ambrosia trifida

Abstract: The objects of this investigation were to determine the direction and magnitude of the gradients in ossmotic values and suction tension values in the aerial portions of Ambrosia trifida L. and to determine the magnitude of the daily and seasonal variations in these values. Ambrosia trifida, commonly known as the giant ragweed or horseweed, was selected for this investigation because the necessary quantity of plant material of uniform quality was available at a relatively short distance from the laboratory. The theory of the "Pull of Transpiration" (6, Ii, I2) has been quite generally accepted as the best explanation of the mechanism by which water ascends to the aerial parts of plants. It is not the aim of this paper to discuss or question this theory. To accept this theory it is not necessary to assume, or even expect, that the highest portions of the plant will have the greatest " lifting power." However, each portion of the plant must be able to raise sufficient water to its own height and must be able to compete for water with other portions of the same plant, particularly when the water supply is deficient. It might be assumed that the tissues capable of exerting the greatest tensions on the water columns will tend to be the most successful in the competition for water. As yet few data are available concerning the relative osmotic and suction tension values in the various portions of the same planlt. Data are lacking particularly from the standpoint of the effect of a deficiency of water on these relative values. Dixon and Atkins (9) studied the seasonal variations in osmotic value of the expressed sap of the leaves of several species of evergreen shrubs. In general, they found these to have a higher osmotic value in winter than in summer. Similar results on other evergreenls were obtained by Lewis and Tuttle (22), Korstian (20), Gail (I5), and others. Meyer (25) has pointed out that the rise in osmotic values in the leaves of evergreens in the winter is largely due to an increase in soluble sugars. Several attempts have been made to determine whether or not osmotic value gradients exist from the root to the apical portions of the plant. Dixon and Atkins (io) showed that the concentration of sugars in the sap of the

Some developmental characters of species of lycoperdaceae

Abstract: Most of the papers on the Gasteromycetes treat them from the standpoint of taxonomy; only a few deal with their morphology and physiology. Of these a few are limited to the Lycoperdaceae. The first reported study of Gasteromycetes was that of Corda (i842), who simply described the germination of spores of Sphaerobolus stellatus Tode. under natural conditions. Sachs (i855) was unable to germinate spores of Crucibulum vulgare Tul. Hoffman (I859) described the germination of the spores of the following species: Lycoperdon echinatum Pers., Lycoperdon gemnm-itatum Batsch., Bovista plumbea Pers., and Cyathus striatus Willd. His later papers (i86oa, i8,6ob) reported his failure to duplicate his first experiments. De Bary in I863, although unable to germinate spores of Phallus impudicus L., gave us the first account of the development of Lycoperdon sp., Bovista plumbea, and Geaster hygrometricus Pers. (see De Bary, i887). Pitra (I870) experimentally verified the previous observations of Corda on Sphaerobolus stellatus. Eidam (i875, i876) produced an oidium-forming mycelium from spores of Crucibulum vulgare and Cyathus striatus. Hesse (i876) obtained a freely branching, oidium-producing mycelium from spores of Cyathus striatus which germinated in water after I8-24 hours. Brefeld ( I877) grew mycelium of unnamed species of Crucibulum and Cyathus from single spores until fruit bodies were formed; these fruit bodies apparently developed in the usual way, but remained empty and failed to mature. Rehsteiner (I 892) gave us the first critical study of species development, using Lycoperdon gemmatum Batsch., Lycoperdon laxums Bon., Bovista plumnbea Pers., and Geaster fornicatus (Huds.) Fr. Rabinowitsch (I894) made a detailed study of Lycoperdon depressurn Bon. Ferguson (I9O2a, I902b) reported that she was unable to germinate spores of Gasteromycetes. Duggar (I9OI, I905) grew tissue cultures of several species, but did not report the formation of any fruit bodies. Molliard (1909), using an entire peridiole of Crucibulumn vulgare, eventually obtained the normal fruiting stage. He did not study the details of development. Cool (I9I2) reported her inability to germinate spores of Gasteromycetes. Cunningham published the details

Nuclear divisions in the tapetal cells of galtonia candicans

Abstract: The increasing number of descriptions of nuclear divisions in tapetal cells has established the fact that these divisions are mitotic rather than amitotic, as was previously considered by many to be the case. Strasburger (I882) described typical mitoses of tapetal nuclei. Duggar (I899) also early described mitoses in the tapetal cells of Bignonia venusta, which are normally binucleate during the stages of microsporogenesis following synizesis. Tischler (I906) described mitotic division of the nuclei in tapetal cells of Ribes. The second nuclear division, however, he found to be amitotic. He also found nuclei with the tetraploid chromosome number and concluded that such nuclei resulted from a fusion of the two diploid nuclei formed after the first division. Winkler (i906) described a fusion of nuclei in the tapetal cells of Wikstroemia indica. Mitotic divisions occur in the tapetal cells, resulting in a 2-6 nucleate condition. These nuclei usually fuse to form giant nuclei, but in some cases they remain separate. Tahara (I9IO) found in Morus indica that during the early stages of the heterotypic division the tapetal cells are binucleate. Their nuclei may fuse to form a single tetraploid nucleus which in turn may divide mitotically, or they may divide separately to form four nuclei. The four nuclei then fuse in pairs, so that each cell contains two tetraploid nuclei which may later divide mitotically. Bonnet (I912) made an extensive study of the tapetal cells in several genera of angiosperms and found mitosis to be the only method of nuclear division in the material examined. In Yu,cca the first tapetal nuclear division occurs before synizesis; in Fuchsia it occurs after synizesis. The second divisions are simultaneous in each cell. In some cases two of the spindle poles converge, so that during the telophases two of the four daughter nuclei fuse to form a single tetraploid nucleus. Thus the cell contains one tetraploid and two diploid nuclei. Bonnet also described a fusion of nuclei in a resting condition which results in the formation of tetraploid and octoploid nuclei. Gates and Rees (192I) found only mitotic nuclear divisions in the tapetal cells of Lactuca. The first division occurs at the start of synizetic contraction, and by the time of maximum synizetic contraction the tapetal cells are all binucleate. Some of them remain binucleate; others undergo a second nuclear division as the pollen mother cells reach the open spireme stage. The

A study of the carpophore of the umbelliferae

Abstract: The carpophore of the Umbelliferae is commonly referred to as an axis or as an axial structure (Lindley, Drude, Gray, Le Maout and Decaisne, Britton and Brown, Hutchinson, etc.). Certain authors go so far as to state definitely that the carpophore is a prolongation of the receptacle between the carpels. Most of them, however, merely call it "axial" or a "central axis." The axial theory of the nature of the carpophore is based apparently on its axis-like appearance and form. This theory, although commonly held, has not been universally accepted, and there have been brought forward other explanations of the morphology of the carpophore. A second interpretation denies the existence of the carpophore as a separate structure and considers it composed of portions of the carpels. The carpophore is, therefore, appendicular in nature, according to the proponents of this second theory, among whom are von Mohl, Van Tieghem, Eichler, and Henslow. This theory rests largely on anatomical evidencethe position and course of the vascular bundles. Other explanations of the carpophore have been proposed but none of these has been of sufficient plausibility to become commonly held. Recent investigations in floral anatomy have clearly demonstrated the fallibility inherent in interpretations of floral structures based mainly on general morphological features. Careful studies of the vascular system of the flower have, in many cases, disclosed the true nature of floral parts which had previously been misinterpreted. The validity of such anatomical evidence is recognized today. It would seem, therefore, that a thorough investigation of the vascular structure of flowers and fruits of representative genera of the Umbelliferae should furnish evidence sufficient to establish the true morphology of the carpophore; and with this in mind the present study was undertaken. Genera from the three subfamilies into which the family is divided were studied, these being so chosen as to include representatives of as many of the tribes as material available permitted. One or more species of twenty-five genera were studied. For the examination of the material there were prepared complete cross-sectional series of flowers and fruits. In the case of most of the species studied, fruits of several ages were cut, including, when possible, mature fruits. Certain of the Umbelliferae show pleomorphism of the flowers with

The development of seeds in certain ericales

Abstract: The ovule of Monotropa Hypopitys is a classic subject of study. It seems first to have been described by Mffller (I847). The development of seeds in this species was described in detail by Koch (I882). Stevens (i9ii) published the first accurate description of the developnment of seed in a species of Ericaceae, Epigaea repens. Samuelsson (I9I3) summarized previous work on the embryology of Ericales and published his own studies of the Scandinavian species. From Samuelsson's work it appears that the course of events is remarkably uniform throughout the order, and that some of the stages are characteristic enough to be diagnostic. A more recent summary is included in Schnarf's (I93I) "Vergleichende Embryologie der Angiospermen."

A comparative histological study of crowngall and wound callus on apple

Abstract: Crowngall is a bacterial disease characterized by the formation of knotty, gall-like malformations on the diseased plant. The prominence of the symptoms and the occasional occurrence of severe epidemics have led to extensive studies extending over a period of many years. The pathogenic nature of the disease was first demonstrated by Smith and Townsend (1907). One of the important developments in the study of crowngall was the discovery that non-pathogenic overgrowths, known as callus knots, may occur on pieceroot grafted apple trees. This fact has obviously raised the question of distinguishing between the two types of overgrowth. Such gross criteria as the hardness of the overgrowth and the character of its surface were found to be unreliable. This uncertainty led to a detailed anatomical study of the different overgrowths. In view of the order in which overgrowths were studied in this laboratory, the present paper will deal first with non-pathogenic callus. Riker and Keitt (I926) and Muncie and Suit (1930) have shown that callus knots are commonly associated with weak graft unions. Fisk (1927) made a preliminary study of overgrowths on apple grafts, and Sass (I932) made a histological study of the healing process during the first growing season in piece-root tongue grafts. Sass described the origin and early stages of development of excess callus. He showed that there is a tendency to produce excess callus wherever there is some obstacle to prompt healing, such as a misfit of the members, or where there is dirt or dead tissue on the plane of contact. He suggested that there are histological similarities between callus knots and certain features of crowngall. The anatomy of crowngall was first studied in detail by Smith and his associates (1912), who found that the gall consists of proliferated tissues of the host. The proliferated mass is at first parenchymatous, but presently differentiation takes place, producing contorted vascular tissues within the gall. Reviews of this phase may be found in papers by Robinson and Walkden (I923) and Hamdi (1930). In view of the fact that the more critical anatomical studies on crowngall were made on plants other than the apple, the present work was limited to the study of pathogenic and non-pathogenic overgrowths on apple grafts. 328

Morphology of the megagametophyte and the embryo sporophyte of isoetes lithophila

Abstract: Isoetes has long been the subject of investigation and discussion, but Hofmeister (io), as a result of his investigations on Isoetes lacustris, gave us in I862 the first detailed account of the life history of the genus; and in most particulars his interpretations have stood as correct up to the present time. He called special attention to the similarities existing between Isoetes and the Lycopods, and pointed out some of the homologies existing between Isoetes and certain Spermatophytes, especially the Conifers. Later morphological studies on Isoetes have been made by Bruchmann (4), Belajeff (2), Kienitz-Gerloff (i i), Farmer (8), Campbell (5), Arnoldi (i), Goebel (9), Scott and Hill (T4), Smith (I5), Stokey (i6), West and Takeda (I7), and, in a limited way, by others. But accounts of detailed studies of the female gametophyte and the embryo sporophyte are pretty well limited to the work of Hofmeister (io), Kienitz-Gerloff (ii), Farmer (8), Campbell (5), and Arnoldi (i). Hlofmeister investigated I. lacustris, a species found in the British Isles and in North and Central Europe. This species, according to Pfeiffer (I3), has megaspores 500-700 microns in diameter. Kienitz-Gerloff also used I. lacustris in his study of the embryo. Campbell worked on I. echinosporca var. braunii (I. brauniii), whose megaspores measure from 420 to 580 microns in diameter. Farmer studied material of I. lacustris, but 'most of his account deals with the development of the organs of the mature sporophyte. Arnoldi made a study of the female gametophyte of I. mtalinvermiana. This form is limited in its distribution to Piedmont, in Italy, and has large megaspores ranging from 66o to 88o microns in diameter. Isoetes lithophila Pfeiffer, used in the present investigation, is apparently limited in its distribution to a sma'l area in Central Texas, and has very small megaspores ranging in size from 290 to 36o microns. The mature gametophyte of this species exhibits a striking abundance o-f rhizoids after the first leaf of the embryo has appeared, as well as a conspicuous protrusion of gametophytic tissue, which for a time encloses the first leaf of the embryo and later remains as a sheath about the base of the leaf until the gametophyte disintegrates. Observation of ftiese prominent features led to the present investigation, and as it progressed, several interesting morpho-

A lycopodiaceous strobilus from the pocono sandstone of pennsylvania

Abstract: Although several instances are known of the occurrence of lycopodiaceous fossils in the pre-Coal Measures rocks of North America evidences of their fructifications are exceedingly rare. For this reason a specimen recently found in the Pocono sandstone and which shows some of its internal organization is of considerable interest. This specimen, along with several other plant fossils, was discovered during the summer of I93I in a small quarry about one and one half miles northeast of Port Allegany, McKean County, Pennsylvania. After they were collected these fossils had come into the possession of Mr. J. C. Galloway of Port Allegany, who, appreciating their possible scientific value, very kindly submitted them to the present author for study. Unfortunately the strobilus had undergone no petrifaction, with the consequence that many of the outstanding features of its internal organization were lost or hopelessly obscured. On the other hand certain structural features are preserved in a remarkable fashion. The strobilus, as shown in text figure i, measures one and three-eighths by four inches. The sides are nearly parallel and the apex is bluntly rounded. Attached to it is a stout peduncle, about three inches long but incomplete, which appears to have had a pith. Whether or not this peduncle bore bracts cannot be determined, but the straightness of it suggests that the strobilus was originally borne in an upright position. The upper half of the strobilus had undergone very little decay and the partial obliteration of the structure was caused rather by the severe flattening to which the strobilus had been subjected. A lengthwise split through this upper portion had exposed the axis (as shown in text fig. i) and by carefully removing some of the attached sporophylls with a small chisel the sporangia could be removed. These sporangia are radially elongated and still retain their spores, but whether they are attached to the upper surfaces of the sporophylls by their full lengths as is characteristic of some lycopods or whether they are attached distally to specialized sporangiophores as in the Calamariae or in Cheirostrobus or distally to the sporophyll as in Spencerites, could not be determined. It is assumed, however, that the former situation existed since there is considerable evidence that the strobilus is lycopodiaceous and belongs to the Sigillariae. The sporophylls are a little more than half an inch long and are borne at right angles to the axis. They are in whorls about three-sixteenths of an inch

Relations of time and maintained temperature to germination percentage for a lot of rice seed

Abstract: In Haasis's (I928) paper on the germinative energy of lots of seed of pitch pine and of other coniferous trees it is stated that a lot of rice seed was included in the experimentation there described, which was carried out at the Laboratory of Plant Physiology of the Johns Hopkins University in I927 and I928. The present paper presents the main results of the experiments with rice there referred to, together with some discussion of relations between time, temperature, and germination percentage. In the preparation of this article we have had critical and bibliographic help from Dr. Thomas I. Edwards, of the School of Hygiene and Public Health, of the Johns Hopkins University. The standard cultures of rice were essentially like the standard cultures of pitch pine seed described by Haasis, and those employed in Edwards's (I933) study of soybean seed were similar in many respects. Each culture regularly contained 50 seeds, taken as a random sample of the lot. After an hour of preliminary soaking, at about 20? C., the seeds were uniformly distributed on agar plates in covered Petri dishes. To the water in which the seeds were to be soaked was added 0.25 g. of " Semesan " powder for each IOO ml. According to the statement of the manufacturers, this material contained 35 per cent, by weight, of hydroxy-mercuri-chloro-phenol. For the agar plates, the granulated preparation called " Bacto-Agar " was used, IO g. for each liter of water, and each culture dish contained 20 Ml. of the mixture. A series of tests at temperatures between 8? and 24? included seed samples soaked in distilled water as well as those soaked in antiseptic solution, but there was no indication of any significant difference between the results froni the two soaking treatments. We may regard the antiseptic treatment as without considerable effect on the results of this study, but it was a regular feature of the experimental background. Tests with seed samples that had not received any preliminary soaking at all gave results that were essentially like those secured with soaked seeds, excepting that the time period needed to give any specified germination percentage with a given maintained temperature was somewhat longer when unsoaked seeds were used, as might be expected. When hulls were removed from the seeds before they were distributed on the plates, without preliminary soaking, the results were like those secured when unsoaked seeds were used with hulls still present.

The morphology of the developing fruiting body of lycoperdon gemmatum

Abstract: Since no work has been done on the morphology and the development of the fruiting body of Lycoperdon gemniatum with the exception of that of Rehsteiner (I892), who studied the gross morphology and chiefly the older stages, it seemed advisable to investigate in detail the successive stages of the development of young basidiocarps fromn the minute primordia to forms with basidia. Interesting problems arose such as the origin of the basidiocarp primordia, the differentiation of the hyphae, the origin and differentiation of the glebal cavities, the binucleate condition, and the presence of hemispherical pads. This led to an investigation of the rhizomorph in connection with the formation of the fruiting body primordia.