STUDIES OF SPORE-PLANTS 



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FIG. 72. A, fern spore germinating; s, spore; rh, rhizoid. B, a later stage of 

 germination; ap.c, apical cell or growing point. C, full-grown pro- 

 thallium, seen from the lower side, many rhizoids, ovaries (ov), sper- 

 maries (sp). D, section of spermary, immature sperm-cells in center ; 

 unshaded cell belongs to the prothallium, beneath which spermaries are 

 suspended. E, a sperm-cell, coiled body, and a group of cilia for use in 

 swimming. F, section of an ovary, with egg-cell (o). The wide-open 

 neck of the ovary is in nature filled with a mucilage through which sperm- 

 cells swim to the ovum. G, prothallium with a young fern plant de- 

 veloped from a fertilized ovum in an ovary, rh, rhizoids ot the pro- 

 thallium; rt, root of the young plant; ct, a cotyledon; st, beginning stem; 

 I, first true leaf forming. (From Parker's Biology, with modifications.) 



