Organography of plants, especially of the archegoniatae and spermaphyta . idium, each of them divides by two anti-clinal walls into the two sterile cells respect-ively b and c, d and e. Fig. 137, B^ and themother-cell of an antheridium out of whichthe two mother-cells of the spermatozoidsare developed. The dorsiventrality of theprothallus is here very apparent. The cellsb, c, d, e, which remain sterile, and which inmy view are wrongly designated wall-cells,take no part in the opening of the anthe-ridium. It is indeed clear that in so small antheridia the openingmechanism may be very simple. On
Organography of plants, especially of the archegoniatae and spermaphyta . idium, each of them divides by two anti-clinal walls into the two sterile cells respect-ively b and c, d and e. Fig. 137, B^ and themother-cell of an antheridium out of whichthe two mother-cells of the spermatozoidsare developed. The dorsiventrality of theprothallus is here very apparent. The cellsb, c, d, e, which remain sterile, and which inmy view are wrongly designated wall-cells,take no part in the opening of the anthe-ridium. It is indeed clear that in so small antheridia the openingmechanism may be very simple. One might endeavour to interpret thissimple structure as not a reduced, but a primitive rudimentary one, inasmuchas it conforms somewhat with that of the antheridia of Algae like Oedogo-nium. But general consideration of the reduction of prothalli makes theview of it as a reduction the more probable, as does also a comparison withwhat is found in the allied (although not very nearly so) Azolla, whosesingle antheridium possesses a lid. The proof of either view is Fig. 137. Salvinia natans. Developmentof the male prothallus. A^ division of themicrospore into three cells I, IT, TIT. B,mature prothallus from the side ; C, matureprothallus from below. Cell /has dividedinto the cells of the prothallus a and />.Cell //has divided into the two sterile cellsd and c, and the two spermatogenous cellsJl, each of which has formed two mother-cells of spermatozoids. Cell ///has dividedinto the two sterile cells d and e and thetwo spermatogenous cells jj. Each pair ofcells J, J, and s^ s., represent one antheri-dium. After Belajeff. A, magnified , and C, magnified 640. Lehrb. THE ARCHEGONIUM 183 B. THE ARCHEGONIUM. The term Archegoniatae used to embrace both the Pteridophyta andthe Bryophyta shows that the structure of the archegonia in both groups isalike. The archegonium of the Pteridophyta has its venter embedded in thetissue of the prothallus. In Marattia and such heterospo
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