LEJEUNEA. 67 
large cells arranged in a beaded line, like the “false nerve” of Frullania 
Tamarisci ; or, in the subgenus Stictolejewnea, solitary, and scattered over 
the leaf at equal intervals, as in the dotted leaves of a Hypericum. Tri- 
gones, so constantly present at the angles of the cells in Frullania, are 
comparatively rare in Lejeunea. The cells of the lobule are much smaller 
than those of the lobe immediately overlying them, so that one cell of 
the latter will sometimes cover 3 to 5 cells of the former. 
The underleaves are either entire (Holostipe) or bifid (Schizostipw)—a 
most important difference, dividing the genus into two primary, and for the 
most part strictly definite groups, each of which includes many natural 
subgenera. The Holostipe belong almost exclusively to the tropics and 
southern hemisphere, only a single species (L. Mackazz) reaching our own 
shores, and two or three others the southern states of N. America. 
Although far less numerous in species than the Schizostipe, they are divi- 
sible into several well-marked groups. The underleaves show several 
other modifications, the principal of which are constant in each subgenus. 
A small and very natural subgenus, Cololejewnea nobis, has the under- 
leaves altogether absent, even from the involucres; but tufts of radicles 
are (or may be) produced at the base of every leaf. A still more remark- 
able group, consisting of two small subgenera (Diplasiolejeunea and Coluro- 
lejeunea) has duplicate underleaves, one to each side-leaf. I know of no 
parallel case in any other genus of hepaticee. Radicles are often copiously 
developed on the underleaves of all prostrate Lejewnea, especially of those 
that inhabit living leaves of trees. In Odontolejewnea they spread out in 
the form of a closely-rayed star, but in most other subgenera they are 
fascicled, or brush-shaped, and in the robuster species, with assurgent 
stems, are rarely present except on the creeping caudex. 
The inflorescence is about equally divided between monoicous and 
dioicous. It is paroicous in only a very few, chiefly of the robuster, 
Species; autoicous almost throughout some subgenera that are mainly 
foliicolous ; dioicous in most species of certain ramicolous subgenera of 
cespitose habit, and in a few species of several others. The andrcecia in 
a few subgenera exist solely in the form of minute whitish catkins ; in 
others they are terminal or medial on the branch or stem, the bracts 
being continuous with the normal leaves and scarcely differing from them 
in size, but nearly equilobed, and rather cymbiform than complicate ; in 
many subgenera, however, both forms co-exist, sometimes on the same 
plant. The ¢ bracts are diandrous in the great majority of species, 
the interpolation of a triandrous bract being exceedingly rare ; a few 
subgenera, however, are constantly monandrous, as already indicated in 
the generic character, and in one subgenus (Harpalejeunea) the antheridia 
are either solitary or twin in nearly every species. The antheridia 
are globose, and the stipes slender; where there are two together, 
one is larger than the other and overarches it on a longer incurved 
stalk. 
The 9 flowers are always terminal on a branch, or (very rarely) on the 
mainstem. The flowering branch, whether long or short, may be either per- 
fectly simple, which is the case in comparatively only a few species, or ¢nno- 
vant, 7.e., continued by an innovation originating immediately beneath the 
perianth, and in many cases itself again and again innovated and floriferous 
at each successive apex. The singular feature in Lejewnea is that the iner- 
most bract is always attached (adnate) to the innovation, and is quite free 
from the floriferous axis except at the antical basal angle. This kind of 
