. Botany for high schools and colleges. Botany. O7MN08PERM^. 397 same figure.) In all cases, unless possibly tlie Gnetaceaefur- nish some exceptions, the pollen grains become more than one* celled before the formation of the pollen tube (Figs. 281-5- 0-7). When the pollen grains germinate—, send out their tubes—they always swell up and burst the extine (which slips off in the ConiferGe), and the intine is then prolonged into a tube, which is continuous with the cayity of the grain, and into which the protoplasmic con- tents pass (Figs. 286 and 287). The small cells take no active part in t
. Botany for high schools and colleges. Botany. O7MN08PERM^. 397 same figure.) In all cases, unless possibly tlie Gnetaceaefur- nish some exceptions, the pollen grains become more than one* celled before the formation of the pollen tube (Figs. 281-5- 0-7). When the pollen grains germinate—, send out their tubes—they always swell up and burst the extine (which slips off in the ConiferGe), and the intine is then prolonged into a tube, which is continuous with the cayity of the grain, and into which the protoplasmic con- tents pass (Figs. 286 and 287). The small cells take no active part in the formation of the tube, and from their similarity, both in structure and function, to the small cells in the germi- nating microspores of the Sel- aginellw, there can be no doubt that they are to be regarded as constituting a rudimentary j^rothallium. 509.—The female flower is in most cases a similar elon- gated axis, upon which are ar- ranged spirally a considerable number of phyllomes, each bearing two or more naked ov- ules. Thus in AMes pectinata the female flower is the young Fig. a bract, c, detached 1 • T -J. J? • from Uieaxis of a youHg cone oi Abies cone, which consists 0± an axis pecUnata, with the scale, s, bearing the (^n V\a- 988 J^\ hp^ivina- -nnv ovules, sA;(enl^irged). iy, upper part of \SPf J^lg. ^00, J3) Dealing nai- a mature cone ; si», axis ; c. bracts ; s, row bracts {c), which, in turn, Sfoa'^thtfp'perSa.^TiSSce'd',': develop thick scales (s, s) upon g/'^^f;; Vvt^g'Trea^ielf-lte; their upper surface. The scales Schacht. nre at first quite small (as in A), and it is only as the cone becomes older that they grow larger. Each scale bears on its inner face two inverted ovules {sh, Fig. 288, A). In Pi7ms sylvestris the structure is essentially the same as. 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 perf
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