No. 551] 



NOTES AND LITERATURE 



(iS7 



found in Biccia. The elaboration of the sporophyte can also be 

 followed. Biccia, as is well known, has the simplest known sporo- 

 phyte, in this respect being in a much lower plane than Sphcero- 

 carpus, although the thallus in the latter is much less specialized 

 than in Biccia. 



The evolution of the sporophyte, as every botanist knows, is 

 associated with a reduction in the amount of tissue devoted to 

 spore-production, and a corresponding increase in the purely 

 vegetative or sterile tissue of the sporophyte. The latter, how- 

 ever, in the Marchantiales always remains relatively simple in 



In the lower Marchantiales the sexual organs are borne upon 

 the dorsal surface of the unmodified thallus, but in the more 

 highly specialized types like Fimbriaria or Marchantia, charac- 

 teristic receptacles are developed, usually composed of a number 

 of very short branches resulting from the repeated dichotomy of 

 the original thallus apex. The classification of the Marchan- 

 tiales has been based largely on the character of the receptacle 

 and the sporogonium. 



Cavers recognizes five families of very unequal size, viz., Ric- 

 ciacea?, Corsiniacese, Targioniaceae, Monocleacese and Marchan- 

 tiaceje. The latter, which aside from the Ricciaceffi, comprises 

 the greater part of the Marchantiales, was divided by Leitgeb into 

 three subfamilies, Astroporse, Operculatse and Composite, but 

 it is very doubtful whether these can be maintained. 



The Ricciacea3, the great majority of which belong to the 

 genus Biccia, are undoubtedly the simplest, and probably the 

 most primitive, members of the order. The extremely *mi P lo 

 sporophyte is almost entirely devoted to spore production, there 

 being no sterile tissue beyond a very imperfect single outer layer 

 of cells. No other liverworts approach the Ricciacea? m the sim- 

 plicity of the sporophyte. 



The second family, Corsiniace*, is intermediate in the struc- 

 ture of the sporophyte, between the Rieciaceae and the higher 

 Marchantiales. 



The third order, Targioniaceae, includes the two small genera, 

 Targionia and Cyathodium. These are very characteristic liver- 

 worts represented in the United States by a single species lor- 

 mania Injpophylla, common in the coast region of California, but 

 absent from the eastern states. This species occurs also in 

 southern and western Europe. Cyathodium includes a tew 



