82 



MOSSES AND FERNS 



CHAP. 



older plant. Leitgeb (Fig. 17, PI. IX.) shows a condition 

 that looks as if at an earlier stage a two-sided apical cell had 

 been present, but he says nothing in regard to this. The 

 sexual organs appear while the plant is extremely small. Leit- 

 geb says he observed the first, indications of them on individ- 

 uals only one millimetre in diameter, and before the first papil- 

 late hair on the ventral surface had been formed. 



In the commonest California!! species, 5\ cristatus the 

 spores separate completely at maturity. The early stages of 

 germination are like those in S. terrestris. There is usually 

 a two-sided apical cell at first, which later is replaced by the 

 type found in the adult thallus. 



FIG. 34. Geothallus tuberosus. A, Male plant, Xis; B, section of female plant, Xi55 



t. young tuber. 



Where there is an excess of moisture the thallus may be- 

 come much larger than usual, this being especially noticeable 

 in the male plants. There is often, under these conditions, 

 a development of leaf-like marginal lobes. This excessive 

 vegetative development of the thallus is accompanied by a 

 marked diminution in the number of the sexual organs. 

 (Campbell (17)). 



Geothallus. 



Evidently closely allied to SpH&rocarpus is a remarkable 

 Liverwort, as yet found only near San Diego, in Southern 



