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Emplectopteridium alatum Kawasaki 的脉序* 总被引:2,自引:2,他引:0
Emplectopteridium alatum Kaw. 的脉序历来被描述为叶脉结网并具邻脉,主要基于具有邻脉这一特征,该种被归于美羊齿类.经笔者研究,这种植物没有邻脉而具伴网眼.这样,不但 E. alatum Kaw. 的分类位置需重新考虑,而且所谓 Emplectopteridium 演化系的基础也就完全瓦解. 相似文献
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Thomas R. Pray 《American journal of botany》1962,49(5):464-472
Pray , Thomas R. (U. South. California, Los Angeles.) Ontogeny of the closed dichotomous venation of Regnellidium . Amer. Jour. Bot. 49(5): 464–472. Illus. 1962.—The venation of the pinna of Regnellidium consists of a flabellate series of dichotomizing vascular strands, branches of a single pinna trace. At the laminal margin, the entire venation is closed by a marginal vein. The development of the pinna was investigated primarily by means of paradermal sections. During early development, the organization of the marginal meristem and its derivatives is very similar to that previously described for Nephrolepis. The arrangement of cells in the embryonic pinna is predisposed for the differentiation of dichotomizing procambial strands. During the final phases of pinna development, the marginal meristem is altered in such a manner as to result in a submarginal band of elongated cells which differentiates a marginal procambial strand connecting the tips of the dichotomizing veins. Relatively late in pinna ontogeny and after the entire procambial venation pattern has been delimited, the marginal meristem becomes inactive. The possible correlation between extended marginal growth and dichotomizing veins is discussed. 相似文献
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张奠湘 《热带亚热带植物学报》1994,2(4):45-57
本文对代表豆科云实亚科紫荆族全部五个属.即紫荆属、腺叶紫荆属、格里芬豆属、拟羊蹄甲属和羊蹄甲属的几乎全部系或亚组的134个种或种下分类单元的叶脉序进行了研究,并描述了本族20个基本脉序类型.在紫荆族中,腺叶紫荆属和拟羊蹄甲属的脉序式样非常相似;紫荆属的种类的脉式样以全绿叶,一级脉不及绿等特征组合有别于本族其它属;格里芬豆属的脉序高度特化,有别于紫荆亚族的所有类群;羊蹄甲属是叶脉序式样最多样化的类群.在羊蹄甲属中,羊蹄甲亚属和显托亚属的脉序式样非常多样化.Elayuna亚属的两个组和Barklya亚属的脉序式样非常相似.Barklya亚属的仅有种了香叶羊蹄甲的脉序仅以其叶全缘区别于Elayuna亚属.脉序性状支持把Cansenia系、白花羊蹄甲系、羊蹄甲系、绿花羊蹄甲亚组、总状花羊蹄甲亚组、Elayuna亚属、伞房系、Chloroxanthae系、棒花系、掌叶组和萼管组等作为自然类群的观点.在本族植物的脉序类型中,一级脉及缘、全缘叶、发育完好的脉岛等性状常相关出现;另一方面,一级脉不及缘,具二小叶或叶深裂,脉岛发育不完善及盲脉多分枝等性状常相关出现.如同形态和花粉性状,脉序性状能为紫荆族的分类提供另一方面的佐 相似文献
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Derral Herbst 《American journal of botany》1972,59(8):843-850
Six species of Euphorbia endemic to the Hawaiian Islands have disjunct veins as a normal component of their foliar anatomy. An ontogenic study of the foliar venation of one of these species, E. forbesii, showed a normal development of the foliar procambium as determined by previous studies of dicotyledonous leaves. The disjunct veinlets are isolated early in the histogenesis of the intersecondary veins when certain procambial cells fail to differentiate into vascular tissue. It appears that these cells develop into normal parenchymatous cells of the ground tissue. It is suggested that these cells are physiologically distinct from the rest of the procambial cells. In no instance was a tracheary element seen which appeared to have arisen independently of the normal procambial reticulum. 相似文献
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Howard J. Arnott 《American journal of botany》1959,46(6):405-411
Arnott , Howard J. (Northwestern U., Evanston, Ill.) Anastomoses in the venation of Ginkgo biloba. Amer. Jour. Bot. 46(6): 405–411. Illus. 1959.—Although the vasculature of the lamina of Ginkgo biloba has been described as open dichotomous and devoid of anastomoses, vein unions were found in a survey of 1065 leaves collected from both long and short shoots of 11 trees. When studied by directing a strong light through the lamina and by clearings, 9.9% of the leaves possessed 1 or more anastomoses. Long shoot-leaves showed 13.4% anastomoses while short shoot-leaves showed 8.2% anastomoses. Multiple anastomoses were found in almost half of the leaves bearing anastomoses. In the 105 leaves having vein unions, 163 anastomoses were counted. These anastomoses could be grouped into 4 types which are easily distinguished by the number of dichotomies involved and by the presence or absence of dichotomies above the point of vein union. Other deviations were found from the “normal” venation pattern; these consisted of unconnected veins, veins anastomosed marginally but unconnected basally, and veins ending a considerable distance from the margin. It was speculated that the anastomoses found in Ginkgo biloba are of a simple, archaic type and are apparently analogous to the anastomoses in the leaves of certain ferns and in the leaflets of various cycads. The evolutionary significance of these anastomoses must be assessed by a broad study of venation patterns in the seed-plants. 相似文献
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独行菜属植物叶片脉序的比较观察 总被引:7,自引:0,他引:7
对独行菜属(Lepidium)8种,1变种进行了叶片脉的比较观察,结果表明:它们的一级脉中等粗细,基部1~2对侧生,一级脉与二级脉连志成拟环结两行羽状脉;三级脉贯穿型或结网型,叶缘末级脉为不完全型,网眼大小,形状不规则,发育均为不完善型,可为探讨十字花科的系统演化提供一些形态学依据。 相似文献
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Arnott , Howard J., and Shirley C. Tucker . (Northwestern U., Evanston, Ill.) Analysis of petal venation in Ranunculus. I. Anastomoses in R. repens v. pleniflorus. Amer. Jour. Bot. 50(8): 821–830. Illus. 1963.—The venation patterns of 1218 petals of Ranunculus repens v. pleniflorus were analyzed, with particular attention to the number and position of vein anastomoses. The essentially open dichotomous vascular pattern is complicated by the presence of vein fusions in 69.4% of the petals. The anastomosis ratio (number of anastomoses/number of appendages) is, therefore, high (1.37), compared to a maximal 0.61 for Ginkgo leaves. Of the petals having such fusions, 55.3% have more than 1 anastomosis; the maximal number of fusions found per petal is 8. The presence of anastomoses shows a high degree of correlation with petal size and petal lobing. The types of fusions (types A, B, C, D) are identical with those found in Ginkgo leaves, with the addition of 2 modifications of type C. Curiously, types C and D account for 98.7% of the total anastomoses, while types A and B are rare. An analysis of the location of each type within the petal shows that type C's are disproportionately numerous along the distal periphery, and that type-D fusions are unusually numerous in the central and basal regions. Such evidence suggests that the occurrence of a vein fusion is no “accident,” but rather that it is one manifestation of morphogenetic control. 相似文献
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Nels Lersten 《American journal of botany》1965,52(8):767-774
The histogenesis of the leaf venation in Trifolium wormskioldii was followed, using whole cleared leaflets and transverse and paradermal microtome sections. Mature leaflets are about 8 mm in length. The midvein precambium appears in leaflets 100 μ in length; secondary vein procambium is first seen in 230 μ leaflets; procambium of minor veins first appears in leaflets 400-600 μ in length. Phloem is apparent before xylem, in midvein, secondary veins, and minor veins. Vein endings are initiated and they mature last. No evidence was found to support the theory of “vein breakage.” In the greenhouse 24 days elapsed from leaf initiation to exposure of leaf tips; 6 more days elapsed until full leaf expansion. 相似文献
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Thomas R. Pray 《American journal of botany》1960,47(5):319-328
Pray , Thomas r . (U. South. California, Los Angeles.) Ontogeny of the open dichotomous venation in the pinna of the fern Nephrolepis. Amer. Jour. Bot. 47(5) : 319—328. Illus. 1960.–The venation of the pinna of Nephrolepis consists of a midvein and 2 lateral series of dichotomizing veins all of which terminate freely near the margins. The development of the pinna is analyzed with particular attention to the nature of the marginal meristem and the organization of the embryonic pinna as it appears in paradermal section. The arrangement of cells in pinna wings during the period of marginal growth displays a pattern which foreshadows the pattern of the mature venation. In contrast with the development of the leaves of angiosperms, marginal growth continues into a relatively late phase of pinna ontogeny and apparently is active throughout the phases of ontogeny concerned with blocking-out the pathways of procambial differentiation. Thus the pattern of venation appears to be correlated with the manner of activity of the marginal meristem and subsequent orientation of its derivatives. The theoretical aspects of the result of this investigation are discussed in relation to other studies of foliar venation ontogeny. 相似文献
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