544 Evans: HEpATICAE OF PUERTO RICO 
Homalo-Lejeunea * is proposed as their practical equivalent. When 
Schiffner + raised Homalo-Lejeunea to generic rank he appreciated 
this fact and designated the genus by the name Marchesinia. Itis 
worthy of note that Spruce’s subgeneric name has never been 
applied to a formally published genus, although species of Homa- 
loleyewnea may be found described in the literature. 
The species of Marchesinia, like those of the preceding genus, 
are among the most robust of the Leyewneae. At the present time 
about fourteen species are recognized ; of these the type species, 
M. Mackaii (Hook.) S. F. Gray, has a local distribution in 
Europe, two are known from Africa, a few others from the 
Galapagos and Hawaiian Islands, and the remainder from tropical 
America. They grow occasionally on rocks but more frequently 
on the bark of trees or on rotten logs, and certain species are 
found on both inorganic and organic substrata. The plants some- 
times grow mixed with other bryophytes but usually form pure 
mats of considerable extent. They are more or less pigmented 
with brown or purple and in some of the species are distinctly 
glossy. 
The stems are at first prostrate and often look very muchas if 
they might belong to the genus Symbiezidium. In most species, 
however, secondary stems are soon developed, which separate 
more or less completely from the substratum, These stems give 
the plants a more characteristic appearance, and in old tufts it 
becomes difficult to find traces of the original prostrate stems. 
The secondary stems are irregularly pinnate and sometimes grow 
for a considerable distance without branching. In most of the 
species the female stems exhibit a striking false dichotomy, owing 
to the development of subfloral innovations in pairs. 
The leaves are more or less imbricated and, so far as their lobes 
are concerned, bear much resemblance to those of the preceding 
genus. In certain species, however, the apical region is constantly = 
or occasionally dentate (PLATE 32, FIGURES I, 2, I 7). The lobule 
exhibit considerable variety in form and in size but possess certain 
structural features in common. In normal cases, for example, the 
free margin bears a distinct apical tooth'; this may be blunt, consist- 
* Hep. Amaz. et And. 132. : 
ft Engler & Prantl, Nat, Pdanzenfam. 13: 128. 1895. 
