This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1908 Excerpt: ...indications there is no evidence among living species of methods of increase in number of sporangia. Even the apical growth of the strobilus itself is, as a rule, strictly limited. Of reduction in number of sporangia there is as little direct evidence, but it is to be remembered that complete abortion leaves no trace ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1908 Excerpt: ...indications there is no evidence among living species of methods of increase in number of sporangia. Even the apical growth of the strobilus itself is, as a rule, strictly limited. Of reduction in number of sporangia there is as little direct evidence, but it is to be remembered that complete abortion leaves no trace of what has occurred (see Chapter X.). On grounds to be mentioned below it would seem probable that such complete abortion of sporangiophores has figured in the evolution of the Equisetales, contributing to the origin of the initial vegetative system of the individual plant. The structure of the mature sporangiophore and of the sporangia in the Calamarians is so similar to that of Equisetum that, taken together 1 Organography, ii., p. 500. Fig. 207. EyuUetum arvensc, L. A, section traversing a sporangium in median longitudinal plane: the cells marked ( X ), like those in rig. 206, are traced in origin from segmentation of superficial cells subsequent to the first periclinal division. B, a similar sporangium cut transversely. X 200. with their insertion directly on the axis, there can be no doubt of their true homology.1 This is illustrated by Scott's figure of the sporangiophore of Calamostachys Casheana (Fig. 210), which shows the position and structure of the sporangia; but the number of the sporangia on each was, as a rule, only four. In some species there was heterospory, megasporangia and microsporangia being found even upon the same sporangiophore: this is illustrated by Scott in Calamostachys Casheana.1 He has also noted in C. Binneyana the abortion of certain spores of the tetrad:3 this, taken with the condition as seen in C. Casheana, indicates that in the palaeozoic genus "we are able to trace how heterospory originated. The fact...
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Add this copy of The Origin of a Land Flora: a Theory Based Upon the to cart. $11.69, very good condition, Sold by John C. Newland rated 4.0 out of 5 stars, ships from Cheltenham, Glos., UNITED KINGDOM, published 1967 by Hafner Publishing Co.
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Seller's Description:
Used-Very Good. Good hardback (no dust jacket) Facsimile of 1935 edition. 'Damaged' stamp on fore-edge-repaired damage at head of front hinge; binding tight; spine a little bumped at head & foot.
Add this copy of The Origin of a Land Flora to cart. $28.17, very good condition, Sold by The Guru Bookshop rated 3.0 out of 5 stars, ships from Hereford, WALES, UNITED KINGDOM, published 1908 by Macmillan.
