Evans: Genus of Hepaticae from Hawaiian Islands 101 



very youngest stage of a flagelliform branch. An apical region, 

 however, in which such a branch is found in the third postical seg- 

 ment from the apical cell, shows the following conditions (Fig. B) : 

 The underleaf developing from the segment (numbered i), is nar- 

 row and bears a single primordial papilla at the apex ; the branch 

 already shows the rudiments of three leaves (numbered la, 2a, 

 and 3a), the oldest being a side-leaf on the side away from the 

 underleaf, the second a side-leaf on the side toward the underleaf 

 and the third an underleaf, distinguishable by its three papillae 



aw 1 4*1. 



A. Normal apical region, X 235. X Apical cell. I, 2, 3, etc. Segments in 

 order of age, 3 and 6 showing the young underleaves, each tipped with three pri- 

 mordial papillae. 



B. Apical region with young branch in third postical segment from apical cell, 

 X 235. X. Apical cell of main axis. I, 4, 7. Postical segments in order of age ; 

 the lateral segments are not numbered as some of the young side-leaves have been dis- 

 sected away ; 1 shows an underleaf with a single primordial papilla, at the side of the 

 young branch. \ a , 2a 9 3^. Segments of branch, 3a showing the first underleaf, with 

 only two of its three primordial papillae visible. 



(only two of which show in the drawing). In this case, therefore, 

 as in the terminal branching from a lateral segment, the third leaf 

 bears the same relation to the flagellum that the underleaf, beside 

 *'hich this specialized branch arises, does to the main axis, and the 

 first two side-leaves are in a corresponding sequence. The same 

 sequence can often be distinguished in an older flagellum (as in 

 Fi S- 4» where the second side-leaf is largely concealed), but 

 m some cases the first kw leaves are so crowded that it is dif- 



ficult to make out their true sequence. From the preparation just 



