SECOND GROUP. 



THE MUSCINEAE'. 



THE Hepaticae (Liverworts) and the Musci (Mosses), which are included under the 

 term Muscineae, are characterised by a very distinctly-marked alternation of 

 generations. The sexual generation which is rich in chlorophyll and self-supporting 

 is not produced directly from the germinating spore, but a simpler structure, in the 

 Mosses usually of a confervoid character, called the protonema, is first produced, and 

 on this the sexual generation arises as a lateral or terminal shoot, which in the 

 Hepaticae is often not very clearly distinguished from the protonema. 



Fertilisation in the female sexual organ of the first generation gives rise to 

 a second generation, a structure of a totally different character, exclusively intended 

 for an asexual production of spores ; this structure is not organically connected with 

 the previous generation, but it derives its sustenance from it, and in outward appear- 

 ance is simply its ' fruit,' like the smaller fructifications of the Thallophytes. To call 

 attention to the peculiar nature of this sporocarp and to exclude all false com- 

 parisons 2 , Sachs has proposed to call it a sporogonium. 



The SEXUAL GENERATION" (oophore, oophyle) produced from the spore with 

 the intervention of a protonema in the Muscineae is either a flat leafless thallus, as in 

 many of the Hepaticae {twisted in the form of a corkscrew in Riella}, or a slender 

 often much-branched leafy stem ; in both cases, which are connected by very gradual 

 transitions, numerous hair-like structures (rhizoids) are usually formed, which fix the 

 thallus 3 or the stem to the surface on which it grows. In many cases the vegetative 

 body is scarcely a millimetre in length, in others it grows into copiously branching 

 forms from ten to thirty centimetres long or even more ; the duration of its life is 

 limited to a few weeks or months in only a few and these the smallest species ; in the 

 majority it may almost be said to be unlimited, for the thallus or leaf-bearing stem 

 continues to grow at the apex or by means of new shoots, termed innovations, while 



1 See my treatise on the Muscineae in Schenk's Handbuch der Botanik, II. Bd., pp. 315-402, 

 [also Encyc. Britann. gth ed.]. 



2 It would be incorrect, for instance, to regard the ' moss-fruitj' as morphologically equivalent 

 to the sporocarp of the Marsiliaceae or to that of the Phanerogams. 



1 The thallus, or thallus-like stem of many Hepaticae was formerly called a frond (fro us} ; but 

 the term is synonymous with thallus and therefore superfluous. 



