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Summary Ultrastructural investigations reveal the presence of transfer cells in tissues belonging to both generations at the sporophyte-gametophyte junction. The foot epidermal cells possess an organelle-rich cytoplasm whereas cells of the vaginula contain more elaborate wall labyrinth. Also visible are differences in the extent of retraction of cytoplasm in these two types of cells.  相似文献   

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《Journal of bryology》2013,35(2):449-454
Abstract

Orthotrichum consimile Mitt. has been found in eight Belgian localities. No differences were found between European and North American plants in the spore diameter and height of the connecting membrane uniting the endostome segments at the base. O. consimile was found at altitudes ranging from 110 to 400 m in disturbed habitats on Sambucus nigra and Salix spp. A map showing its distribution in Europe is given.  相似文献   

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Acylation of 2-amino-1,3,4,6-tetra-O-benzoyl-2-deoxy-α-D-glucopyranose yielded various 2-acylamido-1,3,4,6-tetra-O-benzoyl-2-deoxy-α-D-glucopyranoses, which on treatment with hydrogen bromide-acetic acid gave halogenoses, oxazolinium bromides or 2-bromo-oxazolidinium bromides depending on the N-acyl substituent. It was found that acetyl bromide-hydrogen bromide is a particularly suited reagent for such transformations.  相似文献   

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Acknowledgments

We appreciate the invaluable contributions of the following reviewers during the editing of Vol. 8 Nos. 1–2.  相似文献   

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The survival of the NHS lies largely in the hands of government, and this article suggests steps that it should take to deal with pressures on the NHS in terms of funding, managing efficiency, and demands. Changes to the system of funding may be unfeasible, but management could be improved by research to allow greater understanding of the local effects of national policies. Alternatively health authorities could be given more freedom to manage funds, although this would have to be accompanied by stiff sanctions for those who failed. Demand could be contained by strengthening policies to ensure that new technologies are cost effective. The government could try to reduce demands arising from increased expectations by encouraging informed public debate about priorities and influencing the availability of private health care. All these efforts should be guided by the values underpinning the NHS, which should be debated and decided collectively and confirmed in a new charter for NHS''s 50th anniversary in 1998.  相似文献   

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A. Dorn  P. Hoffmann 《Tissue & cell》1981,13(3):461-473
Deposition, detachment and removal of the three embryonic cuticles are studied. The menbrane-like cuticle 1 covers the embryo during katatrepsis and ‘disappears’ thereafter. Cuticle 2 deposition starts shortly before dorsal closure. Its apolysis is accompanied by contractions of the embryo. Ecdysis of cuticle 2 takes place during hatching. Only cuticle 3 (= first larval cuticle) shows differentiations like sensilla and cornea. Peaks of ecdysteroid (and probably JH) titre are observed during apolysis of cuticle 1 and cuticle 2 (Dorn, 1981). Transition from ectoderm to epidermis proper takes place shortly before and during onset of cuticle 2 synthesis.  相似文献   

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The distinct characters of the flower of Plagiostachys elliptica, S. Q. Tong et Y. M. Xia are: (1) each flower possesses two large lateral staminodes, which are adnate to the lip (labellum) to form a deeply 3 lobed labellum;(2) connective extends into a curved, beak like conspicuous appendage (anther crest) and envelops the upper part of style. In the Zingiberaceae, these characters are only present in the genus Zingiber.Furthermore, in Sect. Pleuranthesis of Zingiber the spike also arises from side of the leafy stem. Pollen grains of the species are with cerebelloid sculpture,that is the character of the Subtype Cerebelloid areolate in Zingiberaceae, and are similar to those sculpture and morphology of Sect. Zingiber of the genus Zingiber and differ from those of Plagiostachys, of which pollen grains are with longer spines and belong to the Group long spinate of Subtype spinate. The endotesta of seeds in this species is composed of one layer of brick shaped parenchymatous cells, which is similar to the parenchymatous endotesta of Zingiber seeds and obviously differs from that of seeds of Plagiostachys, which consists of one layer of sclereids. Therefore,Plagiostachys elliptica S. Q. Tong et Y. M. Xia should be transferred from Plagiostachys to the genus Zingiber, and a new combination——Zingiber ellipticum (S. Q. Tong et Y. M. Xia) Q. G. Wu et T. L. Wu is made in this paper.  相似文献   

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A new species of the isoetalean leaf genus Lepidophylloides is described. This Guadalupian species from the Paraná Basin, Lepidophylloides corumbataensis, found as silicified microphylls in the Corumbataí Formation in the municipality of Piracicaba, São Paulo state, in southern Brazil, is the first species of the genus to be formally described for Brazil, and possibly the first for Gondwanaland. This is also the first time that surviving palisade tissue has been found in a species of Lepidophylloides. The new species is compared to known species and shown to be distinct from all previously described from Euramerican and Cathaysian floras. The organization of the xylem in arch-like or crescent-shaped bundles suggests a relation to Cathaysian species. The close association with Lycopodiopsis derbyi stems (which have true leaf scars and must have suffered leaf abscission) suggests that they are different organs from the same species.  相似文献   

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