52 SURVEY OE THE REPRODUCTIVE PROCESS 



For the normal fructification of mosses a certain dryness 

 and insolation are required. In a moist and gloomy 

 atmosphere the stems, instead of bearing fruit, are con- 

 verted into leafy shoots, from which other like shoots may 

 be budded oif, the pullulation being continued indefinitely, 

 and the development of fructification postponed, till some 

 chano:e occurs in external circumstances. For a time the 

 pullulations continue in adhesion to the parent stock, 

 forming a ramose vegetation, but the common axis being of 

 a perishable nature they are eventually set free by its 

 decay. In this way even mosses which rarely fructify 

 may extend themselves very widely, rivalling, as has been 

 remarked, the largest forest trees, both in the space covered 

 by their derivative phytoids, which physiologically are 

 parts of themselves, and in their aggregate longevity. 

 Free gemmee, also, which are detached at once to form 

 new plants, are not uncommon, both among mosses and 

 Hepaticse. 



§ 7. REPRODUCTION IN FILICES AND EQUISETACE^. 



In these orders we have antheridia and archegonia, 

 bearing a general resemblance to those of mosses ; they 

 are not formed, however, in connection with the leafy axis, 

 which bears only the gemmae known as spores, but in 

 minute detached parenchymatous phytoids, termed pro- 

 thallia, into which the spores germinate, and from which 

 the embryo emerges as the result of impregnation. 



Two views may be taken of the homologies subsisting 

 between these plants and the mosses. A physiological 

 correspondence being admitted by all between the gemmi- 

 parous production of spores in both cases on the one hand, 

 and the formation of antheridia and archegonia on the 

 other, some eminent cryptogamists — as Hofmeister and 



