The encyclopdia britannica; a dictionary of arts, sciences, literature and general information . simplest cases the sides and base of the chambers perform the workof assimilation ( Corsinia). Usually the surface is extended bythe development of partitions in the chambers (Reboulia), or by thegrowth from the floor of the chamber of short filaments of chloro-phyWous cells (Targionia. Marchantia, fig. 6). The stomata may besimply surrounded by one or more series of narrower cells, or, as inthe thallus of Marchantia and on the archegoniophores of other forms, may become barrel-shaped structure
The encyclopdia britannica; a dictionary of arts, sciences, literature and general information . simplest cases the sides and base of the chambers perform the workof assimilation ( Corsinia). Usually the surface is extended bythe development of partitions in the chambers (Reboulia), or by thegrowth from the floor of the chamber of short filaments of chloro-phyWous cells (Targionia. Marchantia, fig. 6). The stomata may besimply surrounded by one or more series of narrower cells, or, as inthe thallus of Marchantia and on the archegoniophores of other forms, may become barrel-shaped structures by the division of thering of cells bounding the pore. In some cases the lowermost circleof cells can be approximated so as to close the pore. In Dumortierathe air-chambers are absent, their formation being only indicatedat the apex. The sexual organs are always situated on the morphologicallyupper surface of the thallus. In Riccia they are scattered singlyand protected by the air-chamber layer. The scattered position ofthe antheridia is also found in some of the higher forms, but usually. From Strasburgers Text-book of Botany. Fig. 6.—Marchantia polymorpha. (X 240.) A, Stoma in surfaceview. B, Air-chamber with the filaments of assimilating cells andstoma in vertical section. they are grouped on special antheridiophores which in Marchantiaare stalked, disk-shaped branch-systems (fig. 5). The individualantheridia are sunk in depressions from which the spermatozoidsare in some cases forcibly ejected. The archegonial groups inCorsinia are sunk in a depression of the upper surface, while inTargionia they are displaced to the lower side of the anterior endof a branch. In all the other forms they are borne on special arche-goniophores which have the form of a disk-shaped head borne on astalk. The archegoniophore may be an upgrowth from the dorsalsurface of the thallus ( Plagiochasma), or the apex of the branchmay take part in its formation. When the disk, around whicharchegon
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectencyclo, bookyear1910
