. A manual of botany. Botany. PTEBIDOPHYTA im Fig. 883. and fleshy {fig. 917,^), when it is developed underground and contains no chlorophyll. It is always known as the pro- thallium. In the heteroporous forms there are two kinds of prothallia formed, one from the microspore, and the other from the macrospore. In neither case do we get the prothallium entirely set free from the spore. They are not very strongly developed, only sufficiently so indeed to permit of the production of the sexual organs. The pro- thaUium from the microspore gives rise to antheridia ; that from the macrospore to arch
. A manual of botany. Botany. PTEBIDOPHYTA im Fig. 883. and fleshy {fig. 917,^), when it is developed underground and contains no chlorophyll. It is always known as the pro- thallium. In the heteroporous forms there are two kinds of prothallia formed, one from the microspore, and the other from the macrospore. In neither case do we get the prothallium entirely set free from the spore. They are not very strongly developed, only sufficiently so indeed to permit of the production of the sexual organs. The pro- thaUium from the microspore gives rise to antheridia ; that from the macrospore to arche- gonia. In some of the iso- sporous forms the prothaUia, which are all alike as to their vegetative features, are mo- noecious, producing both an- theridia and archegonia ; m others, as in the equisetums, they are dioecious, only bear- mg one or other of them. The antheridia are either immersed in the substance of the prothallium, as in the tuberous forms, or project from the surface as in the flattened ones. They are superficial always in their origin, and consist of a wall of a single layer of cells, which/?,,,, gag. Gametophyte produced by the encloses a number of spirally macrospore of Salvinia. pro. Prothallium ., , -,- ,-n .1 -1 bearing !n, young sporophyte. After coiled ciliated antnerozoiQS pringsheim. (fig. 860, b). The archegonia are also superficial, having a venter embedded in the tissue of the prothallium, and a slightly projecting neck consisting of only a small number of ceUs {fig. 897). The structure is otherwise like that of the Bryophytes. Fertilisation is effected in the same way as in the latter group. The number of archegonia produced often depends upon whether or no the oospheres of the first-formed ones become fertilised. If not, others are developed. Vegetative reproduction of the gametophyte is not uncommon. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appea
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbotany, bookyear1895
