98 PLANT STRUCTURES 



it multiplies the product of the sexual spore. A glance at 

 the formula given above shows that if there were no sporo- 

 phyte (S) the oospore would produce but one gametophyte 

 (G). By introducing the sporophyte, however, as many 

 gametophytes may result from a single oospore as there are 

 asexual spores produced by the sporophyte, which usually 

 produces a very great number. 



In reference to the sporophytes and gametophytes of 

 Bryophytes two peculiarities may be mentioned at this 

 point : (1) the sporophyte is dependent upon the gameto- 

 phyte for its nourishment, and remains attached to it ; 

 (2) the gametophyte is the special chlorophyll-generation, 

 and hence is the more conspicuous. It follows that, in a 

 general way, the sporophyte of the Bryophytes only pro- 

 duces spores, while the gametophyte both produces gametes 

 and does chlorophyll work. 



It is important also to note that the protected resting 

 stage in the life history is not the sexual spore, as in the 

 Algae, but is the asexual spore in connection with the 

 sporophyte. These spores have a protecting wall, are 

 scattered, and may remain for some time without germi- 

 nation. 



If the ordinary terms in reference to Mosses be fitted 

 to the facts given above, it is evident that the " moss 

 plant " is the leafy branch of the gametophyte ; that 

 the " moss fruit " is the sporophyte ; and that the alga- 

 like part of the gametophyte has escaped attention and 

 a popular name. 



The names now given to the different structures which 

 appear in this life history are as follows : The alga-like part 

 of the gametophyte is the protonema, the leafy branch is 

 the gametophore ("gamete-bearer") ; the whole sporophyte 

 is the sporogonium (a name given to this peculiar leafless 

 sporophyte of Bryophytes), the stalk-like portion is the 

 seta, the part of it imbedded in the gametophore is the 

 foot, and the urn-like spore-case is the capsule. 



