. An introduction to vegetable physiology. Plant physiology. REPRODUCTION 431 opens a little at the apex when the archegonia are mature, in order that fertilisation may be possible. "When we pass to the Phanerogams two further advances may be seen. The spore never escapes from the sporangium, and the prothallium does not emerge even in part from the spore, which does not open. In these plants the megaspore is represented by the cell known formerly as the embryo-sac, the sporangium being the ovule. Among the Phanerogams we have two types of prothallium which are characteristic of the Gyvmo
. An introduction to vegetable physiology. Plant physiology. REPRODUCTION 431 opens a little at the apex when the archegonia are mature, in order that fertilisation may be possible. "When we pass to the Phanerogams two further advances may be seen. The spore never escapes from the sporangium, and the prothallium does not emerge even in part from the spore, which does not open. In these plants the megaspore is represented by the cell known formerly as the embryo-sac, the sporangium being the ovule. Among the Phanerogams we have two types of prothallium which are characteristic of the Gyvmosperms and the. Fig. 177-—Germination of Megaspore of arch archegonia; oos, oospheres; em', embryo. The spore has been ruptured and the upper portion removed. i Angiosperms respectively. Fig. 178 shows the structure in the former ; the spore or embryo-sac is filled with the pro- thallium, formerly called the endosperm, at the apex of which are several archegonia each containing a female gamete or oosphere. After fertilisation the resulting zygote gives rise to a young sporophyte or embryo, which becomes embedded in the endosperm. The structure thus formed, consisting of the sporangium or ovule, with the solitary spore it contains, the latter having in its interior the embryo surrounded by the prothallus, constitutes the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Green, J. Reynolds (Joseph Reynolds), 1848-1914. Philadelphia, P. Blakiston
Size: 1585px × 1576px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1900, bookdecade1900, booksubjectplantphysiology
