LIVERWORTS 123 



Some species are found associated with Mosses, growing 

 amongst their stems and leaves, and appearing delicate, 

 pale, and even threadlike by contrast with their sturdier 

 associates. Other species grow flattened and branching 

 on the trunks of trees, still others on almost bare soil, 

 and some are aquatic. The Liverworts are well de- 

 scribed as amphibious; they are mostly terrestrial, but 

 as their male elements, the spermatozoids, are biciliate, 

 and must needs swim to the archegonia in order to fer- 

 tilize the egg-cells, the plants are aquatic so far as 

 dependence upon a sufficiency of water for this purpose 

 is concerned. 



Strasburger, in his Textbook of Botany, divides the 

 Hepaticse into four Orders : The Ricciacece, the Marchan- 

 tiacece, Anthocerotacece, and the Jungermanniacece. 

 Kerner adopts the same divisions. Professor D. H. 

 Campbell, in his Structure and Development of Mosses 

 and Ferns, divides the Liverworts into two Orders, 

 the Marcliantiales and Jungermanniales, and questions 

 whether the Anthocerotes should not properly be taken 

 out of the Liverworts entirely, and be given a place 

 intermediate between them and the Ferns, etc. In the 

 present sketch it will be sufficient for us to follow the 

 divisions of Strasburger. 



The Ricciacece. — There are 110 species in this Order, 

 no less than 107 belonging to the genus Riccia. The 

 majority of these are small. They are of the thalloid 

 type, and occur in the form of small rosettes on clay 

 soil. Riccia natans is aquatic, and floats on the surface 

 of water like Duckweed ; R. fluitans grows submerged in 

 water; but both species can adapt themselves to damp 

 soil, on which they, like most Riccias, form flat rosettes 



