Text-book of botany, morphological and physiological . capsule increases, thecentral cell first divides into two, and then, by successive bipartitions, into eightspore-mother-cells, which become isolated in the cavity of the sporangium which isfilled with granular fluid, and assume a round form. The inner parietal layerremains in the condition of a delicate epithelium till the time of the formation ofthe spores, but disappears when they are ripe; so that here also the wall of thesporangium finally consists of only one layer. In Marsilea and Pilularia, where theenvelope of the sporocarp is very
Text-book of botany, morphological and physiological . capsule increases, thecentral cell first divides into two, and then, by successive bipartitions, into eightspore-mother-cells, which become isolated in the cavity of the sporangium which isfilled with granular fluid, and assume a round form. The inner parietal layerremains in the condition of a delicate epithelium till the time of the formation ofthe spores, but disappears when they are ripe; so that here also the wall of thesporangium finally consists of only one layer. In Marsilea and Pilularia, where theenvelope of the sporocarp is very hard, it remains thin and colourless, the sporangiaforming small hyaline sacks; in Salvinia, where the \vall of the sporocarp is thinand delicate, the cells of the wall of the sporangium assume, at the period of ripe-ness, greater consistency and a bro\vn colour, as in Ferns. Until the commence-ment of the division of the spore-mother-cells into four, the development ofall the sporangia proceeds similarly; the differentiation into macrosporangia and. FlC. 295.—Transverse section of the sporocarp oi Pilulariai^lohiili/era below the middle, where the macrosporang^ia andmicrosporanjjia ma and 7ni are intermingled ; g the fibro-vascular bundles, h hairs, e epidermis of tlie outer surface. 39<5 VASCULAR CRYPTOGAMS. microsporangia arises, at least according to observations made on Pilularia, in thefollowing manner^: — If a microsporangium is about to be formed, each of themother-cells is broken up into four tetrahedral spores, which all develope intomicrospores; in the macrosporangium, on the contrgjy, the mother-cells remain,with one exception, undivided; this one first of all divides in exactly the samemanner as the mother-cells of the microspores (Fig. 297, /); but only one of the four daughter-cells developes any further;in the three others the formation of arough exospore is commenced coveredby an outer gelatinous layer; this lattersoon becomes absorbed, the three aborti
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
