BRYOPHYTES 



77 



produces spores. The gametophyte is the more conspicu- 

 ous generation on account of food manufacture, which de- 

 mands a display of green tissue, and therefore among Liver- 

 worts the gametophyte is thought of usually as " the plant," 

 and the sporophyte as its " fruit." Of course the sporo- 

 phyte is in no sense a " fruit," for it has no more connection 

 with the gametophyte than a parasite has with its host. 



Since gametophytes and sporophytes will be changing 

 in appearance and relative prominence as we proceed through 

 the higher groups, it is well to begin with a sure rule for 

 recognizing them. Whatever a fertilized egg produces, no 

 matter what it looks like, is a sporophyte ; and whatever 

 a spore produces, no matter what it looks like, is a gameto- 

 phyte. If this rule is remembered, the two generations will 

 be recognized in spite of all their disguises. 



47. The Mosses. The Mosses are much more abundant 

 now than the Liverworts, and are able to live in much more 

 exposed places. In fact, Mosses are as- 

 sociated with Lichens in the ability to 

 live in conditions that are impossible 

 for other plants. That ancient Liver- 

 worts were the ancestors of Mosses is 

 generally believed, and the first question 

 is as to the differences that distinguish 

 Mosses from Liverworts. 



It will be remembered that in some 

 Liverworts the disk bearing the sex- 

 organs is lifted up from the rest of the 

 body by a long stalk (Figs. 53 and 54). 

 Since this stalk bears the sex-organs 

 (which contain the gametes), it is called 

 a gametophore (" gamete-bearer"). In 

 the Mosses this gametophore always 

 appears, but instead of being a naked stalk, as in Liver- 

 worts, it is covered with numerous small leaves (Fig. 59). 



FIG. 59. The leafy gam- 

 etophore (leafy branch) 

 of a moss rising as a 

 branch from the pros- 

 trate filamentous body. 



