28 i 
Evans.—■Vegetative Reproduction in Metzgeria. 
becomes broader, the costa appears or increases in complexity, postical 
hairs and slime papillae are formed, and the differentiated thallus soon 
shows the normal branching by dichotomy. The course of development, 
however, is usually affected by two tendencies, both of which seem to be 
especially potent in the present species. One of these is the tendency 
towards reversion, which has already been discussed under some of the 
preceding species ; the other is the tendency which the apical region shows 
of acquiring the characteristics of permanent tissue, thus bringing the 
growth of the young thallus to an end. The cessation of growth and 
division in the apical cell may take place in any stage of differentiation, 
and is apparently associated with an early development of secondary 
gemmae. 
Metzgeria oligotricha, sp. nov. Pale green, growing in depressed mats: 
thallus prostrate, repeatedly dichotomous and frequently giving off ad- 
ventive branches from the postical surface of the costa, well-developed 
branches about 1-5 mm. wide, up to 4*5 mm. long between the forks, plane 
or nearly so ; costa bounded both antically and postically by two rows of 
cortical cells; wings usually from ten to fifteen cells broad, the cells 
thin-walled throughout, averaging about 55 x 37 /z and not varying much 
in size in different parts of the thallus ; hairs few and irregularly scattered, 
restricted to the margin and to the postical surface of the costa, the marginal 
hairs often from 150 to 300 /z long, slender, straight or irregularly curved, 
but never hooked at the apex, usually truly marginal, but sometimes 
displaced to the postical surface: inflorescence dioicous : ? branch broadly 
orbicular-obovate, about 0*23 mm. long, with numerous long hairs on the 
margin and postical surface ; calyptra clavate, about 1 mm. long, sparingly 
pilose: cf branch not seen : sporophyte (not quite mature) showing an oval 
capsule about 35 x 28 /z and a stalk about 30 /z long : gemmae marginal, 
broadly ligulate, usually one cell thick throughout, stalk distinct, apical cell 
single, hairs marginal, not displaced, scattered, long and straight. 
On trunks of trees. Cuba : without definite locality (Wright, Hep. 
Cubenses, distributed as M. furcata , mixed with Dendroceros Breutelii and 
other Bryophytes). Jamaica: Morce’s Gap, July 12, 1903 (A. W. E., 
No. 37, mixed with M, hamata). Porto Rico: Mount Morales, near 
Utuado, March 19, 1906 (Howe, No. 1118). The specimens from Jamaica 
may be considered the type. 
In the structure of its costa M. oligotricha agrees with both M. uncigera 
and M. hamata. It differs from M. uncigera in its larger size and larger 
alar cells, and in its longer marginal hairs which are never hooked at the 
apex even on the gemmae. The latter are also distinguished by their early 
development, the original projecting cell not undergoing a preliminary 
division before functioning as the mother-cell of the gemma. It differs 
from M. hamata in its plane thallus and in its sparse marginal hairs which 
are never geminate. From M. furcata, with which it is also allied, it differs 
in the structure of the costa, which is bounded postically by two instead of 
