Anatomy of the Dicotyledons.
About: This article is published in American Midland Naturalist.The article was published on 1950-11-01. It has received 2511 citations till now.
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TL;DR: Rays composed of upright cells, nonconversion of the uniseriate rays to multiseriate or heterocellular rays, and decrease in vessel element and tracheid length with age are generally accepted criteria for paedomorphosis in dicotyledonous woods.
Abstract: Wood and bark of 12 collections ofEmpetraceae representing three genera containing seven species (one with two subspecies) are analyzed with respect to quantitative and qualitative features. Empetraceae have vessels somewhat angular in transection, with scalariform perforation plates and scalariform to opposite vessel-ray pitting. Imperforate tracheary elements are all tracheids. Axial parenchyma is sparse and not subdivided. Rays are characteristically uniseriate and composed of upright cells (older stems have rays with both upright and procumbent cells). These features ally Empetraceae closely to Ericaceae and Epacridaceae. The narrow vessels, quite numerous per mm, denote a high degree of wood xeromorphy; growth rings and tracheid presence also may be indicative of adaptation to drought or physiological drought due to cold. Rays composed of upright cells, nonconversion of the uniseriate rays to multiseriate or heterocellular rays, and decrease in vessel element and tracheid length with age are generally accepted criteria for paedomorphosis in dicotyledonous woods, and these apparently apply to Corema and Empetrum as well as small shrubs similar to them: Cassiope (Ericaceae), Empleuridium (Celastraceae), Myrothamnus (Myrothamnaceae), and Tetratheca (Tremandraceae). Data on bark are presented for all taxa ofEmpetraceae.
19 citations
TL;DR: The morphological and palynological evidence positions Warionia between the tribes Cardueae and Cichorieae suggesting that it could be a remnant of the ancestral stock that gave rise to both tribes.
Abstract: The genus Warionia , with its only species W. saharae , is endemic to the northwestern edge of the African Sahara desert. This is a somewhat thistle-like aromatic plant, with white latex, and fleshy, pinnately- partite leaves. Warionia is in many respects so different from any other genus of Asteraceae, that it has been tentatively placed in the tribes Cardueae, Cichorieae, Gundelieae, and Mutisieae. Until now, a comprehensive study of Warionia to have a complete context for discussing its taxonomic position is lacking. The general morphology, anatomy, palynology and chromosome number of W. saharae are investigated here, and the species is described and illustrated. Laticifers in leaves and stems indicate a relationship with Cichorieae, and are associated with the phloem, in contact with it or with the surrounding sclerenchyma sheath. The pollen features indicate a strong relation with Cardueae, namely the structure with Anthemoid pattern where the columellae are joined to the foot layer, the ectosexine with thin columellae, the endosexine with stout and ramified columellae, the conspicuous spines with globose bases and conspicuous apical channels, and the tectum surface very perforate. Chromosomal counts resulted in 2 n = 34. The morphological and palynological evidence positions Warionia between the tribes Cardueae and Cichorieae suggesting that it could be a remnant of the ancestral stock that gave rise to both tribes.
19 citations
Journal Article•
TL;DR: The xylem structure of Eliaea shows more primitive features than that of Cratoxylum, but the flowers seem to be more specialized, and the possible implications of these findings for plant geography are discussed.
Abstract: The floral and vegetative anatomy of the closely allied guttiferous genera Cratoxylum (Indo-Malesia) and Eliaea (Madagascar) is described. Although the two taxa have many features in common, differences are substantial enough to recognize them as distinct genera, as appears from the following survey: Cratoxylum Ovary with 12 or more ovules Ovary with 3(or 4) incomplete true septa Styles and filaments glabrous Secondary xylem with scarcely pitted fibres Vessels solitary and in radial multiples Silica bodies present in ray cells of wood Eliaea Ovary with 6(—8) ovules Ovary with 6(or 8) incomplete septa, three being true, three false Styles and filaments mostly villous Secondary xylem with densely pitted fibretracheids Vessels almost exclusively solitary Silica bodies absent The vascularization and insertion of the hypogynous scales in both genera favours the view that these structures may be interpreted as staminodial derivatives. In some species of Cratoxylum a further differentiation into taxa of lower rank is suggested by the presence or absence of abaxial epidermal papillae on the leaves; this is related to geographical distribution. Floral and xylem specialization of Cratoxylum and Eliaea are discussed. The xylem structure of Eliaea shows more primitive features than that of Cratoxylum, but the flowers seem to be more specialized. The possible implications of these findings for plant geography are discussed. In Cratoxylum the section Isopterygium (C. arborescens and C. glaucum) is very different in its wood anatomy from the other representatives of Cratoxylum. This difference (concerning parenchyma distribution) is correlated with the evergreen habit in the section Isopterygium. The other sections of Cratoxylum are deciduous. A comparison with some data from literature about other groups with deciduous and evergreen members is made.
19 citations
Cites background from "Anatomy of the Dicotyledons."
...Detailed data on xylem specialization are to be found in Bailey and Tupper (1918), Frost (1930), Tippo (1938), Metcalfe and Chalk (1950), and Carlquist (1961)....
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...Detailed data on xylem specialization are to be found in Bailey and Tupper (1918), Frost (1930), Tippo (1938), Metcalfe and Chalk (1950), and Carlquist (1961). For our purpose it suffices to summarize the following trends: 1) long fusiform elements (particularly vessel members) are more primitive than short...
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TL;DR: Al accumulation is almost limited to the subfamily Rubioideae, however, not all tribes show the character, especially the predominantly herbaceous Anthospermeae, Paederieae, RubieAE, and Spermacoceae.
Abstract: The chrome azurol-S test, which is a chemical spot-test for Al accumulation in wood, was applied to 443 wood samples of members of the Rubiaceae. A positive reaction was found in 103 specimens. Comparison of the results with earlier analyses of leaves of Rubiaceae shows that Al accumulation occurs more frequently in leaves than in wood. The strongest Al accumulators occur in the neotropical genera Psychotria subg. Heteropsychotria, Coussarea, Faramea, and Rudgea. The distribution of Al accumulators is discussed in view of recent tribal and subfamilial classification of the Rubiaceae. The major conclusion is that Al accumulation is almost limited to the subfamily Rubioideae. Within the Rubioideae, however, not all tribes show the character, especially the predominantly herbaceous Anthospermeae, Paederieae, Rubieae, and Spermacoceae. Al accumulation in the Urophylleae, Pauridiantheae, Craterispermeae, and Knoxieae supports earlier associations of these tribes with the Rubioideae.
19 citations
TL;DR: Investigation of the stem anatomy confirms the relationship with Sarcostigma, especially the presence of successive cambia, but the new genus differs, amongst other anatomical characters, in lacking islands of included phloem within the xylem.
Abstract: A new genus of Icacinaceae, Sleumeria, is described from northern Borneo. The only known species, Sleumeria auriculata, is a large woody scrambler with spirally arranged leaves with entire margins and prominent reticulation, hairs that dry a distinctive yellow-brown, and racemose or compound racemose inflorescences. The habit, leaf arrangement, and inflorescence type place Sleumeria in a group of climbing Icacinaceae near to Sarcostigma, but it is distinguished from that and other closely related genera by the combination of distinctly pedicellate flowers arranged singly or in pairs along the inflorescence rachis, swollen sagittate anther connectives, and a spherical ovary with a distinct filiform style with an unlobed stigma. Investigation of the stem anatomy confirms the relationship with Sarcostigma, especially the presence of successive cambia, but the new genus differs, amongst other anatomical characters, in lacking islands of included phloem within the xylem.
19 citations