EvaANs: HEPATICAE OF PuERTO RICO | 281 
into approximately equal quadrants. Then, as Stevens goes on 
to show, the two apical quadrants grow more rapidly than the two 
basal quadrants, thus forcing the wall between them into an oblique 
position with respect to the median walls. The two apical quad- 
rants function as apical cells, the first segment in each being 
cut off by a wall parallel to the median wall. The segments under- 
go further divisions, the first walls being always periclinal. The 
basal quadrants also become subdivided in much the same way as 
the oldest segments. The eccentrically situated stalk cell is 
approximated more or less to the basal margin (TEXT FIGURE 2, 
C, D), and the gemma becomes free by a splitting of the walls by 
which it is attached to the stalk cell. 
When the gemmae of various species are compared it is found 
that they differ in size and in the number of cells of which they 
are composed, but that, for a given species, the number of cells 
is fairly constant. The differences in the number of cells are due 
primarily to the number of segments cut off by the apical quadrants 
and secondarily to the number of subsequent divisions which take 
place in the segments and in the basal quadrants. In the simplest 
gemmae only two segments are cut off, each of which divides once, 
while each of the basal quadrants divides into three cells, the first 
division being by the usual periclinal wall and the second by an anti- 
clinal wall in the outer cell. These divisions give rise toa gemma 
composed of sixteen cells, a condition seen clearly in A phanole- 
jeunea microscopica, A. exigua, Cololejeunea myriocarpa, and C. 
Macounii (Spruce) Evans;* occasionally, in C. myrtocarpa at least, 
one.or both of the younger segments fail to divide, so that the 
mature gemma consists of only fourteen or fifteen cells. It will 
be seen that gemmae of this type tend to be symmetrical with 
respect to a transverse median plane as well as a longitudinal plane 
(TEXT FIGURE I, A—C; PLATE 12, FIGURE IO). 
The cutting off of three segments takes place in the gemmae 
of Cololejeunea calcarea, C. Biddlecomiae, Leptocolea ovalifolia 
(Evans) comb. nov.,t and L. cunetfolia (TEXT FIGURE I, D, £). 
*Mem. Torrey Club 8: 171. pl. 22. f. 1-8. 1902. Leleunis  (Cololejeuneo) 
Macounii Spruce in Underwood, Bull. fans Club 17: 259. 1890. The species is 
probably a Leptocolea, pn from its vegetative structure; unfortunately mature 
perianths have not been seen by the writer. It is known from British Columbia aA 
= Cololejeunea iaaitidie Evans, Trans. Conn. Acad. 10: 450. pl. 58. 5 Pe 
1900. Known from the Hawaiian Islands only. 
