Hepaticae : Yale Peruvian Expedition of ipii. 301 



A gemma at maturity consists of a circular or slightly elongated 

 plate of cells with a single apical cell and a short and often indistinct 

 stalk composed of two cells (Fig. 1, B). It is further characterized 

 by being distinctly concave and by bearing a few rudimentary mar- 

 ginal hairs, slightty displaced to the concave surface. 



The germination of a gemma is very similar to that described for 

 other species. The concave surface becomes attached to the sub- 

 stratum b}' means of the rudimentary hairs, which grow out into 

 short rhizoids. The apical cell of the gemma then resumes its divi- 

 sions and gives rise to a flat strap-shaped thallus, which is at first no 

 wider than the gemma but which graduall}' becomes wider and differ- 

 entiates a costa. In rare cases the young plant undergoes a branch- 

 ing by an apparent dichotomy before the costa makes its appearance. 

 It is often quite impossible to determine where the gemma ends and 

 the young thallus begins, but sometimes there is a constriction at 

 the junction between the two. In some cases new marginal gemmae 

 arise, either on the original gemma itself or on the young thallus 

 while still in an undifferentiated condition. 



The gemmiparous branches (Fig. 1, A) tend to differ more or less 

 from normal branches. They not only curve away from the sub- 

 stratum but totally lack hairs on both wings and costa. At the same 

 time the wings grow narrower and narrower until they may be only 

 three or four cells wide. With this tapering of a branch its growth 

 soon comes to an end. These modifications resemble somewhat those 

 found in the gemmiparous branches of M. fruticulosa (Dicks.) Evans, 

 but apparently they never pass beyond the stages described and never 

 reach the striking conditions sometimes seen in M. fruticulosa, where 

 the branch may lose its wings altogether and become reduced to a 

 radial costa bounded by cortical cells and growing at right angles 

 to the substratum. Whether these apparent differences are actual 

 or merely due to an insufficient supply of the new species can hardly 

 be answered at the present time. 



In his Species Hepaticarum Stephani^ describes two dioicous South 

 American species in which the scattered marginal hairs occur singly. 

 They agree further with M. scyphigera in the costa, which is bounded 

 both above and below by two rows of marginal cells and which bears 

 hairs on its lower surface. One of these species is M.chilensis Steph., 

 of Chile and New Zealand, and the other is M. aurantiaca Steph., 

 of Brazil. In M. chilensis, however, the thallus is almost revolute, 

 the wings are smooth on the lower surface, the cells measure 54 X 36//, 



Bull, de I'Herb. Boissier 7 : 937, 938. 1899. 



