316 Alexander W. Evans, 



The specimens are sterile but are apparently referable to this 

 species. It was originally described from Peruvian material in 

 the herbarium of Kunze. It is now known to have a wide distribu- 

 tion in tropical America and has been reported from Mexico, 

 Colombia, Brazil, and Ecuador, as well as from Peru. 



X, Dicranolejeunea (Spruce) Schiffn. 



Several genera of the Lejeuneae have recently been discussed 

 at length by the writer in connection with the Hepaticae of Porto 

 Rico. Since Dicranolejeunea has not yet been detected on that 

 island the present opportunity is taken of calling attention to its 

 peculiarities. So far as known the genus is entirely tropical in its 

 distribution. In his Species Hepaticarum Stephani recognizes 

 three species from Africa, three from Asia, and twenty-two from 

 North and South America, thus showing its preponderance in neo- 

 tropical regions. The species flourish best at relatively high alti- 

 tudes, alto ugh a few have been reported from near the sea level. 

 The bark of trees is the favorite habitat for the majority of the 

 species ; a few grow on the leaves of woody plants or on rocks ; while 

 others form more or less compact tufts on banks rich in humus. 

 Sometimes a species is able to grow on several substrata. 



Under favorable conditions the plants show a yellowish or brownish 

 pigmentation. Apparently in all cases the stems are at first pros- 

 trate, and oftentimes this habit is retained through life. In other 

 cases the prostrate stems give rise to erect, ascending, or pendulous 

 branches, or secondar}^ stems, which become subdivided and con- 

 tinue their growth indefinite!}'. Under these circumstance it may 

 become difficult or impossible to demonstrate the prostrate stems 

 at all. A similar distinction between a primary prostrate axis 

 and secondary stems occurs in many genera of the Hepaticae, 

 such as Porella, Mastigolejeunea, and Bryopteris. Sometimes it 

 represents a constant feature of an entire genus; sometimes, as 

 in Dicranolejeunea, it is restricted to certain species. 



The branching in Dicranolejeunea is of two types, just as in 

 Stictolejeunea, Bryopteris, and most species of Brachiolejeunea. 

 The Frullania type, in which a leaf without a lobule is situated 

 at the base of the branch, occurs on robust shoots and is associated 

 with vigorous growth (Fig. 7, B; 8, C). The Radula type, in 

 which the leaf at the base of the branch bears a distinct lobule, 

 occurs on older shoots, especially where the development of re- 

 productive organs brings about a retardation or cessation of growth. 



