202 Evans: Notes on genus Herberta 



in much the same way. The entire cell-cavity is eventually lined 

 by a uniformly thick layer of deposit, the only thin places left 

 being the pits in the vertical walls (Text figs 5,6). Even some 

 of the pits may be obliterated with age. When this takes place 

 the deposit either fills the pit-chamber altogether or bridges it 

 across, leaving a minute vestige of the chamber next to the closing 

 membrane (Text fig. 7). When the cells are mature it is some- 

 times possible to detect evidences of the original bands of thicken- 

 ing and of the scallops along the vertical walls, but the free walls 

 present an absolutely uniform appearance. Although the thick- 

 enings look very much as if they were formed by the coalescence of 

 trigones and intermediate thickenings, it is clear from their 

 method of development that they are not directly comparable 

 with the trigones and intermediate thickenings of other Hepaticae. 



Although the description just drawn from //. juniperina prob- 

 ably applies in its essential features to the entire genus, the 

 details are not always as clear in some of the other species. In 

 H. adunca, for example, it is difficult to demonstrate bands of 

 thickening except in the basal portion of the vitta, and it is doubtful 

 if they ever form complete rings. The scalloped appearance of 

 the vertical walls is likewise much less evident. Possibly the more 

 indefinite conditions found are associated with the fact that the 

 thickening of the walls in H. adunca is usually much less marked 

 than in //. jitniperma. 



The leaf surface in Herberta, the so-called cuticle of authors, is 

 striolate or verruculose. The roughness is sometimes very ap- 

 parent and sometimes made out with difficulty. Whether dififer- 

 ences in the degree of roughness yield constant dififerential char- 

 acters in separating species is perhaps doubtful, although such 

 differences seem very striking when certain species are compared. 



The androecia in Herberta are relatively short and usually 

 include from four to eight pairs of bracts, those at the upper and 

 lower ends being somewhat transitional in character. The male 

 plants tend to produce smaller leaves than female plants or vigor- 

 ous sterile plants, and although the bracts are considerably larger 

 than the leaves borne between the successive androecia, they 

 scarcely equal in size the normal leaves on female individuals. 

 Several years ago Schiffner made the remarkable discovery that 



