THE GAMETOPHYTES OF SELAGINELLA 



335 



There are some other life habits of Selagmella wonderfully 

 suggestive of the way in which seed and the seed habit arose. 

 It is known in some species, as S. rupestris, that the micro- 

 spores are thrown out from the sporangia on the upper part of 

 the cone and sift down like pollen grains among the megaspores 



EMBRYO 

 SPOROPHYTE 



FIG. 290. The gametophytes and embryo of Selaginella 



A, male gametophyte contained within the microspore: p, persistent nucleus of 

 prothallial cell ; s, two groups of sperm mother cells. 7>, two-ciliate sperms. 



C, female gametophyte containing an embryo sporophyte: o, archegonium ; 

 r, rhizoids. D, young sporophytes held by the spore leaves of the cone. E, a 

 young sporophyte still attached to the megaspore. B, after Belajeff ; A, C, 



D, adapted after notes and sketches of Miss Lyon 



