126 STKUCTURAL BOTANY 



is true, contains chlorophyll in its outer layer, and so 

 can do some assimilation on its own account, but for the 

 bulk of its food it must rely on the store produced by 

 the thallus. Spore - production is the one function of 

 the fruit; all the parts foot, seta, and capsule are 

 means subservient to this end ; there is no vegetative 

 development worth mentioning. This is the great 

 characteristic, not merely of the Liverworts, but of the 

 Bryophyta generally the oophyte is the prominent 

 vegetative generation, while the sporophyte has little 

 more to do than to discharge its purely reproductive 

 functions as a spore-producing organ. The fruit, indeed, 

 is not always so simple as that of Pellia, but still the 

 same rule holds good. We see, then, that in this sub- 

 kingdom we have to do with plants in which the 

 sexual generation is readily comparable to that of the 

 higher Cryptogams, while the product of fertilisation 

 the sporophyte is developed on entirely different lines. 

 The Muscinese, or Bryophyta, are in fact plants with a 

 well-marked alternation of generations, in which the 

 sexual generation is the more conspicuous and indepen- 

 dent. The distinction between Bryophyta and Vascular 

 Cryptogams is so sharp and constant that the gulf 

 between them has been spoken of as the deepest in the 

 vegetable kingdom. 



B. THE MOSSES 



TYPE VIM. FUN ARIA HYGROMETRICA 



The true Mosses, the general appearance of which will 

 be familiar to everyone, are more highly organised plants 

 than the Liverworts, but at the same time are more 



