100 Evans : Genus of Hepaticae from Hawaiian Islands 



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apical cell divide in the usual way into one internal and two ex- 

 ternal cells. One of these two cells, however, and, apparently, in 

 most cases, the postical one, grows wider than the other and re- 

 divides, so that the segment shows three external cells side by 

 side. These three cells correspond with the three teeth at the 

 apex of the mature leaf. In the Hawaiian plant, three external 

 cells are likewise formed in the lateral segments (Fig. A, segment 



7) 



undivided, the three cells, 



therefore, not giving rise to distinct teeth. This difference is 

 probably not very significant as several species of Bazzania with 

 undivided leaves have been described. In each postical segment 

 of B. trilobata y one internal and two external cells are formed in 

 the same way as in the lateral segments, but here each of the 

 superficial cells grows wider and divides into two, and the seg- 

 ment shows, therefore, four cells side by side. Each of these 

 cells gives rise to a primordial papilla,* and these four papillae 

 are pushed out by the developing underleaves. The process is, 

 however, irregular, and the lobes of the underleaves often grow 

 out beyond the papillae, leaving them at some little distance from 

 the apex. In each postical segment of the new genus, only three 

 external cells are formed, just as in the lateral segments (Fig. A, 



segment 6). Each gives rise to a papilla and the three papillae 



are carried up side by side on the apex of the developing under- 

 leaf, which remains broad and undivided (Fig. A, segment 3 ; 

 Fig. B, segment 4). These three primordial papillae enable us to 

 distinguish at a glance a young underleaf from a young side-leaf, 

 and traces of them may often be detected even in a mature under- 

 leaf. 



The branching from the lateral segments is the same in both 

 genera and has been briefly described above. It may be remarked, 

 however, that in a branch of this sort, the leaves always maintain 

 a definite sequence ; the first leaf is always an underleaf, the sec- 

 ond leaf is a side-leaf on the side of the branch turned toward the 

 main axis, and the third leaf is a side-leaf on the side of the branch 

 turned away from the axis. The third leaf, therefore, bears the 

 same relation to the branch that the narrow leaf does to the axis. 



In my study of the new genus, I have been unable to find the 



* Leitgeb, /. c. 2 : 15. 



