REMAEKS ON THE PTERIDOPHYTES 169 



is the Fern-Plant, and it early becomes independent of 

 the gametophyte. The Fern is more of a land plant 

 than the Moss, and it stands for a distinct advance in 

 the progress of land conquest by plant-life. But if the 

 Pteridophytes generally display advance upon the 

 Bryophytes, it is equally true that there exists abundant 

 evidence of advance in their own ranks. The homo- 

 sporous forms have prothalli of relatively large size, 

 upon which in most instances male and female organs 

 grow in association. There is evidence of the separation 

 of the sexes upon different prothalli in these forms, but 

 it is significant only as a mild attempt at a separation 

 which is successfully achieved in the heterosporous forms. 

 We are reminded of the old legend, which has it, in 

 regard to man and sex, that the original men were un- 

 sexual, but, in course of time, each was cleft in twain 

 by the gods, one half becoming male and the other 

 female. In the plant realm we have asexual plants, 

 sexual plants without sex-difEerentiation, and plants in 

 which such differentiation becomes more and more pro- 

 nounced. The heterosporous Pteridophytes are a dis- 

 tinct advance upon their homosporous allies. In the 

 latter, sex-distinction does not appear in the sporophyte, 

 it becomes evident only in the sexual generation; but in 

 the former, the sporophyte — i.e., " the plant " — bears 

 female megaspores and male microspores, so that sex is 

 apparent in the heterosporous forms in both generations. 

 The well-nourished megaspore illustrates the emphasis 

 which Nature has learned to place upon a sex which has 

 to do so much for posterity. The facts brought out in 

 relation to the partial germination of the megaspores of 

 Selaginella, while still in situ, are extremely significant; 



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