. Lectures on the evolution of plants. Botany; Plants. 140 EVOLUTION OF PLAJTTS except for the conspicuous lobes referred to above. The reproductive organs are very much like those of the eusporangiate ferns, and the spermatozoids, which are large and multiciliate, closely resemble those of Fig. 36 (EquisetinesS). — A, upper part of a sporiferous shoot of ahorse- tail {Equisetum pratense), showing the division into nodes and inter- nodes, the rudimentary sheath-leaves, sh, and the strobilus or cone of sporophylls, c; B, a cross-section of an internode of M. maximum, showing the arran
. Lectures on the evolution of plants. Botany; Plants. 140 EVOLUTION OF PLAJTTS except for the conspicuous lobes referred to above. The reproductive organs are very much like those of the eusporangiate ferns, and the spermatozoids, which are large and multiciliate, closely resemble those of Fig. 36 (EquisetinesS). — A, upper part of a sporiferous shoot of ahorse- tail {Equisetum pratense), showing the division into nodes and inter- nodes, the rudimentary sheath-leaves, sh, and the strobilus or cone of sporophylls, c; B, a cross-section of an internode of M. maximum, showing the arrangement of the vascular bundles, v, and the air-spaces, or lacunae, I; C, longitudinal section of the apex of a young shoot of E. maximum, showing the single large apical cell, x; T>,a, single sporophyll of the same species with the sac-shaped sporangia, sp; E, median sec- tion of the sporophyll; F, a ripe spore, with the elaters, el. The sporophyte, however, shows many points of dif- ference which are early manifest. Thus, in the embryo, it is the stem-quadrant which grows most actively, while the development of the leaves is subordinated to it, as it is throughout the life of the sporophyte. In- stead of the short stem and large leaves of the ferns, the stem in Equisetum is very much elongated, while the leaves are reduced to the toothed sheaths which sur-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Campbell, Douglas Houghton, 1859-1953. New York, London, The Macmillan company
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Keywords: ., bookcentury1900, bookdecade, booksubjectbotany, booksubjectplants
