CHAPTER II 



MUSCINEyE (BRYOPHYTA) HEPATIC^ MARCHANTIACE^ 



The first division of the Archegoniatae, the Muscineae or 

 Bryophyta, comprises the two classes, Hepaticae or Liverworts, 

 and the Musci or Mosses. In these as a rule the gametophyte 

 is much more developed than the sporophyte, and indeed in 

 many forms the latter is very rarely met with. They are 

 plants of small size, ranging in size from about a millimetre 

 in length to 30 centimetres or more. A few of them are 

 strictly aquatic, i.e. Riella and Ricciocarpus among the Hepa- 

 ticae, and Fontinalis of the Mosses ; but most of them grow 

 upon a solid substratum. A favourite position for many is 

 the trunks of trees or rocks. Many others grow upon the 

 earth. They vegetate only when supplied with abundant 

 moisture, and some forms are very quickly killed if allowed to 

 become dry ; but those species which grow in exposed places 

 may be completely dried up without suffering, and some of 

 those that inhabit countries where there are long dry periods 

 may remain in this condition for months without losing their 

 vitality, reviving immediately and resuming growth as soon as 

 they are supplied with the requisite moisture. 



The germinating spores usually produce a more or less 

 well-marked " protonema," from which the gametophore arises 

 secondarily. The protonema sometimes is persistent and forms 

 a dense conferva-like growth, but more commonly it is tran- 

 sient and disappears more or less completely after the 

 gametophore is formed. No absolute line, however, can be 

 drawn between protonema and gametophore, as the former 

 may arise secondarily from the latter, or even from the 

 sporophyte. With very few exceptions, i.e. Buxbaumia, the 



