Evans .— Vegetative Reproduction in Metzgeria. 287 
which develop from them are subject to reversion. The production of 
new gemmae on a young and undifferentiated thallus is very unusual. 
When they do occur they are invariably marginal. 
Metzgeria vivipara, sp. nov. Yellowish or brownish green, growing in 
depressed mats: thallus prostrate, repeatedly dichotomous, well-developed 
branches about 1*5 mm. wide and from 1*5 to 3-5 mm. long between the 
forks, plane or nearly so; costa bounded above by two rows of cortical 
cells and below by four rows (rarely only two or three) ; wings mostly from 
twenty to twenty-five cells broad, the cells thin-walled throughout or with 
very minute trigones, averaging about 35 x 25 /z, slightly smaller towards 
the margin ; hairs restricted to the margin and to the postical surface of 
both wings and costa, the marginal hairs often absent altogether, when 
present usually few and scattered, up to 150 /z long, straight or nearly 
so, sometimes truly marginal, but often slightly displaced to the postical 
surface, alar surface hairs and costal hairs usually more numerous than the 
marginal hairs, but sometimes more sparingly developed : inflorescence 
dioicous: ? branch orbicular-obovate, about 0*25 mm. long, sparingly 
pilose on margin and postical surface: cF inflorescence and sporophyte not 
seen : gemmae numerous, arising from the antical surface of the wings, 
ligulate, one cell thick except at the very base, stalk poorly defined, apical 
cell single, hairs marginal, short, hooked at the apex, usually single, but 
occasionally twinned, sometimes displaced to one surface. 
On trunks of trees. Porto Rico : Barceloneta, April 19, 1887 
(Sintenis, No. 144, distributed as M. furcata ); Utuado to Adjuntas, 
March 21, 1906 (Britton and Cowell, No. 1242). The second specimens 
may be considered the type. 
In its vegetative structure, M. vivipara shows a close relationship to 
M. furcata, the costa being built up according to a similar plan and the 
distribution of the hairs being much the same. It may be at once 
distinguished, however, by its antical gemmae with their slight cell- 
differentiation and hooked marginal hairs. Among other species with 
antical gemmae its closest ally is apparently M. crassipilis , which has a 
similar costa, and also bears hairs on the postical surface of the wings. The 
gemmae will serve at once to separate the two species ; in M. vivipara 
these are ligulate and bear hooked hairs, while in M. crassipilis they are 
orbicular and the hairs are straight. 
Metzgeria Liebrnanniana , Lindenb. & Gottsche. 
According to Stephani the range of this species extends from Mexico 
to Chile and eastward into Brazil. The specimens here described were 
collected in Contreras, Mexico, on October 15, 1908, by Barnes and Land 
(No. 430). They bear gemmae in great abundance. The gemmiparous 
branches, as in the two preceding species, are very slightly modified. In 
some cases a tendency towards a decrease in the number of cortical cells 
along the antical surface of the costa becomes apparent. On normal 
