CRYPTOGAMS 



349 



406. The sporophyte. — The spores found in such abun- 

 dance on the fertile pinna; are all alike, and each one is 

 capable of germinating and continuing the work of reproduc- 

 tion as effectually as the sexual spores of the bryophytes. 

 The fertile frond, or part of a frond, on which they are borne 

 is called a sporophyll (spore-bearing leaf), and the entire 

 plant is the sporophyte, which, with its crop of spores, makes 

 up one generation. 



It is important to observe that in the ferns and in all pteri- 

 dophytes the sporophyte is the conspicuous and highly 

 organized body that is commonly recognized as the normal 

 growing plant; while with the bryophytes just the reverse 

 holds true, — the sexual generation, or gametophyte, repre- 

 sents the normal plant structure, while the sporophyte is 

 an insignificant appendage 

 which never attains an 

 independent existence. 

 Broadly speaking, in bryo- 

 phytes, it is a spore fruit ; 

 in the pteridophytes and 

 spermatophytes a highly 

 developed plant. 



407. The gametophyte. 

 — When one of these asex- 

 ual spores germinates, it 

 produces, not a fern plant 

 like the one that bore it, 

 but a small, heart-shaped 

 body like that shown in Fig. 501. Examine one of these bod- 

 ies carefully with a lens. Observe that there are no veins nor 

 fibrovascular bundles, and the whole body of the plant seems 

 to consist of one uniform tissue. Compare it with the forked 

 apex of a branching thallus of a liverwort. Do j^ou perceive 

 any points of similarity ? The two are, in fact, morphologi- 

 cally the same. This heart-shaped body is called a prothal- 

 lium, and is the gametophyte of the fern. It may be of 



501 



502 



Figs. 501, 502. — Prothallium of a common 

 fern (Aspidium): 501, under surface, showing 

 rhizoids, rh, antheridia, an, and archegonia, 

 ar ; 502, under surface of an older gameto- 

 phyte, showing rhizoids, rh, young sporo- 

 phyte, with root, w, and leaf, b. 



