. Principles of the anatomy and physiology of the vegetable cell. Plant cells and tissues. THE VEGETABLE CELL. 129 ' nation resembling that we observe in the spore. Bat the pollen-grain does not seem to be capable of a farther deyelopraent, under fayourable external cireumstances^ into a plant like the parent, yet Reisseck and Karsten observed that under certam circamstance&, e. ^., when pollen-grams were enclosed in hollow stems like that of the Dahlia, their inner coat was ca]}able of an abnormal development, and of conversion into lower forms of Fungi. ** The OduU. The Ovule {ovulwm, El
. Principles of the anatomy and physiology of the vegetable cell. Plant cells and tissues. THE VEGETABLE CELL. 129 ' nation resembling that we observe in the spore. Bat the pollen-grain does not seem to be capable of a farther deyelopraent, under fayourable external cireumstances^ into a plant like the parent, yet Reisseck and Karsten observed that under certam circamstance&, e. ^., when pollen-grams were enclosed in hollow stems like that of the Dahlia, their inner coat was ca]}able of an abnormal development, and of conversion into lower forms of Fungi. ** The OduU. The Ovule {ovulwm, Elchen),—of late years called by the ad- herents of Schleiden's theory of impregaation the seed-bud (samen- knospe) or gemraule, consists essentially of a parenchymatous papilliform growth from the ovary, of the so- called nucleus (ei-kerne, nucleus ovuli fig. 52, Fig. 52. a), the tercine of Mirbel, in which towards the epoch of impregnation one cell becomes more enlarged, displacing a greater or smaller portion of the parenchyma of the nucleus and forming the emhryo-sac (the quintine of Mirbel). In far tlie greater number of cases the ovule does not stand still at this first stage, in wMcli it consists merely of a naked nucleus, but un- dergoes, before impregnation, a more or less extensive series of changes, which relate partly Transverse section of to the formation of enveloping, membranes, en- Imb^o^^'^rm^rioat closinot the nucleus, and partly to alterations of of the ovuie 'iprmnm); f> V n. ^ ^ 1 jfii I'jy* ."» Outer Coat (,v In the majority of ovules, a second coat (fig. 52, d) is formed in the same way, lower down than the first (fig. 52, e) which it encloses. That part of the ovule where the simple or double coat is connect- ed with the base of the nucleus (fig. 52, /), is named the chalaza, and when beneath this there exists a cylindrical portion, it is called the funiculus (nahelstrang, fig. 52, g), Ohserv, Since the changes of form, which the ovules of most
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