Taxilejeunea pterogonia and certain allied species* 
ALEXANDER W. Evans 
(WITH PLATE 2 AND TWENTY-TWO TEXT FIGURES) 
The genus Taxilejeunea includes some of the largest and most 
conspicuous of the Lejeuneae with bifid underleaves. Some of 
the species abound in tropical regions, especially in mountainous 
localities, and sometimes form broad mats, with or without ad- 
mixture, on rocks, banks and other suitable substrata. The 
color is usually a pale yellowish or whitish green, contrasting with 
the surrounding vegetation. In spite of their large size the 
plants give an impression of great delicacy. When dry the leaves. 
tend to roll themselves about the stem but, when moist, spread 
out more or less widely. The lobules, when normally formed, 
are inflated and show a hyaline papilla at the base of the apical 
tooth, agreeing in this respect with Lejeunea, Rectolejeunea, Pyc- 
nolejeunea and other genera of the Lejeuneae Schizostipae. 
Unfortunately the lobule is often reduced to a minute basal 
tooth and fails to exhibit any distinctive features. The under- 
leaves are unusually well developed and sometimes approach 
or even equal the leaves in size; in other cases they are distinctly 
smaller. 
One of the most distinctive features of the genus is found in 
the branches which bear the female inflorescences. In typical 
cases these are short and have distinctly smaller leaves than the 
stem. The female inflorescence invariably innovates, commonly 
on one side but occasionally.on both, and the innovations are 
usually short and soon brought to an end by another inflorescence. 
In this way more or less complicated branch-systems of a cymose 
character are formed. In many cases the branch-system forms a 
distinct sympodium with the inflorescences ranged along its. 
upper side. In some of the species which have been referred to 
Taxilejeunea, the described conditions are not clearly exhibited- 
* Contribution from the Osborn Botanical Laboratory. 
. 107 
* 
