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102 Evans : Genus of Hepaticae from Hawaiian Islands 



described, it is clear, therefore, that the postical segment which is 

 to give rise to a flagellum first divides in the usual way into one 

 internal and two external cells, but that the external cell which 



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normally broadens out and redivides, here develops at once into a 

 branch, leaving only one cell to give rise to the primordial papilla 



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and underleaf. It should be noted also that the flagellum some- 

 times occurs on the right side of the underleaf and sometimes on 

 the left side, and that both conditions are occasionally found on 

 the same stem. 



.The peculiar branching just described is of particular interest 

 because it shows that the terminal branching of Leitgeb is not 

 restricted to the postical half of a lateral segment, as that author 

 supposed, but may also occur in either half of a postical segment. 

 The fact that these branches are always specialized as flagellar is 

 undoubtedly due largely to their place of origin, and does not 

 affect the point in question. It is, of course, possible that this 

 same type of branching may yet be detected in other genera of the 

 leafy Hepaticae. 



The cells of the Hawaiian plant, as is the case with so many 

 alpine and arctic species, are interesting for their extremely thick 

 walls. The thickening is particularly well seen in the cuticle of 

 the leaves. On both surfaces these are densely covered with ver- 

 ruculae which are very distinct on young leaves but become more 

 or less obliterated with age. The trigones of the leaf-cells (Fig. 

 5) are also conspicuous and project out into the cell-cavities, which 

 are usually distinctly stellate. The trigones are sometimes circular 

 or oval in outline and sometimes tri- or quadri-lobed. Between the 

 trigones the walls are less thickened and sometimes remain very 



Along 



(Fig. 6) 

 difficult 



it is usually 

 In the cells 



of the axis the thickening is also very 4 pronounced (Fig. 7). The 

 superficial cellsare here isodiametric, but the internal cells are several 

 times as long as broad. Except for the strongly developed cuticle 

 the thickening is irregular and the cells are provided with pits, 

 which occur in both transverse and longitudinal walls. 



The essential characters of Austin's species, both generic and 

 specific, are given in the following description : 



