. Morphology of spermatophytes. [Part I. Gymnosperms]. Gymnosperms; Plant morphology. OYCADALBS 11 or they may occur in definite groiips of two to five, wliicli may be called sori, as in Cycas, Stangeria, and Zamia (Fig. 9). The first full account of the development of the microspo- rangium was published by Treub ^â ^ in 1881, who investigated especially Zamia muricata. The latest investigation is that of Stangeria paradoxa by Lang,^^ who has confirmed Treub's re- sults in a general way, and has cleared up certain points which were doubtful. The first indication of a sporan- gium is the differ
. Morphology of spermatophytes. [Part I. Gymnosperms]. Gymnosperms; Plant morphology. OYCADALBS 11 or they may occur in definite groiips of two to five, wliicli may be called sori, as in Cycas, Stangeria, and Zamia (Fig. 9). The first full account of the development of the microspo- rangium was published by Treub ^â ^ in 1881, who investigated especially Zamia muricata. The latest investigation is that of Stangeria paradoxa by Lang,^^ who has confirmed Treub's re- sults in a general way, and has cleared up certain points which were doubtful. The first indication of a sporan- gium is the differentiation of a hypodermal plate of cells (four in Stangeria), which constitutes the archesporium (Fig. 10). This arche- sporium has been homologized with the hypodermal plate of cells which appears in the development of the microsporangia of heterosporous Pteridophytes. It should be remem- bered, however, that the periblem always gives rise to the archespori- um, and that this region, in the ab- sence of a dermatogen, is superfi- cial in the Pteridophytes. It would seem to follow, therefore, that a true homology would regard the archesporium as superficial in Pteri- dophytes and hypodermal in Sper- matophytes. In presenting Treub's results for Zamia, in which the archesporium is spoken of as a hypo- dermal group of cells, GoebeP'^ re- marks that " there is without doubt a unicellular ; In Stangeria, however, Lang was unable to trace the plate of four cells to a single one, and a one-celled archesporium for the micro- sporangia of Cycads still remains to be proved. Each cell of the archesporial plate divides by a periclinal wall into a tabular outer and a larger inner cell (Fig. 10). The outer daughter plate is sterile, and there is no evidence that it contributes to the sporogenous tissue, as in some Pteridophytes. It is com-. FiG. 8.âZamiamwricata: A, stam- inate strobilus, two thirds nat- ural size; B, transverse section of ^ ; C, single peltate stame
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Keywords: ., bookauthorcoulterj, bookcentury1900, bookdecade1900, bookyear1901
