Evans: HEPATICAE OF PUERTO RICO 285 
next the median wall. The corresponding segment on the other 
side of the gemma divides in the same way but the outer cell does 
not become modified. It will be seen at once that when three 
organs of attachment are present the gemma shows a condition 
of slight asymmetry, in spite of the fact that the cells on each side 
of the median wall are alike in number and position. When four 
organs are present the condition of symmetry is maintained. 
Although the gemmae in the Lejeuneae have been but little 
studied by taxonomists it will be seen from the above account that 
they present characters of great constancy. They can often, in 
fact, be used in the determination of specimens which are sterile 
or otherwise imperfectly developed. This is true, for example, of 
the closely related Cololejeunea minutissima and C. myriocarpa, 
where the lobules are usually either rudimentary or abnormally 
developed. To summarize what is known about the Puerto Rico 
species it may be stated that only five of the species described 
in this paper have been proved to be gemmiparous. In the 
gemmae of two of these, Cololejeunea myriocarpa and Leptocolea 
Jooriana, no organs of attachment are present and the margin 
is crenulate throughout; in the other species, C. diaphana, L. 
scabriflora, and A phanolejeunea exigua, the gemmae develop three 
such organs and only certain of the marginal cells project. With 
regard to the number of segments cut off by the apical quadrants, 
A. exigua and C. myriocarpa have only two, C. diaphana almost 
invariably has three, while L. scabriflora and L. Jooriana have four. 
The germination of the gemmae was studied by Goebel in the 
case of L. Goebelii. He found that the apical cells first cut off 
a series of segments but that very soon one of them gave rise to 
the leafy shoot, and he considered that the tetrahedral apical cell 
of the stem was cut out directly from the two-sided apical cell 
of the gemma. Occasionally he saw the leafy plant arise from 
one of the cells next the median wall between the two basal organs 
of attachment. The writer has been able to confirm these obser- 
vations but can add very little to them. It may perhaps be of 
interest to note, however, that in gemmae with three organs of 
attachment the leafy shoot usually arises from the apical cell on 
the side with two such organs. 
YALE UNIVERSITY. 
