Evans: HepaTicaAE oF Puerto Rico 509 
turn it and at the same time to carry it a short distance away from 
its parent axis. 
By means of the discs on the underleaves, which have the 
power in common with rhizoids of secreting a gelatinous substance, 
the propagulum attaches itself firmly to the substratum. Some- 
times the attachment is made still firmer by rhizoids which grow 
out from the marginal cells of the disc (f 73). In the similar 
discs of Odontolejeunea the power of developing rhizoids is pos- 
sessed by all the cells of the disc, instead of by the marginal cells 
alone, as in these propagula. When the propagulum has thus 
established itself, its growing region continues to develop and pro- 
duces an axis bearing normal leaves and underleaves. 
The propagula of L. stenophylla are less highly specialized than 
those of the two preceding species. The branches upon which 
they are developed usually bear abortive leaves, consisting of a 
short lobe and an extremely rudimentary lobule, and the -growth 
of these branches is soon arrested by the production of the pro- 
pagula. In this species the first underleaf is larger than the suc- 
ceeding ones and shows a well-developed disc. The lobes of the 
first and second side-leaves are squarrose and more or less toothed 
and the lobule of the first leaf at least is very rudimentary. The 
third leaf, however, and sometimes even the second, develop nor- 
mal lobules, and the fourth and fifth leaves show fairly character- 
istic lobes. 
Leafy propagula of the type just described occur also in sev- 
eral species of Drepanolejeunea, Their discovery may likewise be 
expected in other epiphyllous Lejeuneae and especially in those 
which do not develop disc-shaped gemmae. ‘ 
YALE UNIVERsITy. 
Explanation of Plates 
The figures were drawn by the writer with the aid of the camera lucida. Most of 
them were prepared for reproduction by Miss Edna L, Hyatt. 
PLATE 23 
Leptolejeunea exocellata (Spruce) Evans. 1. Stem with two perianths, a 2 in- 
florescence and a S inflorescence, postical view, X47. 2. Cells from middle of lobe, 
X 425, 3- Cells from apex of lobe, 300. 4. Cells from base of lobe, showing 
ocellus partially overlapped by adjacent cells, 400. 5. Transverse section 
through lobe and lobule, showing basal ocellus, 300. 6. Apex of lobule, >< 300. 
