Evans .— Vegetative Reproduction in Metzgeria. 277 
same plan, is much more remote. In this species the thallus is strongly 
convex, the marginal hairs are longer and occur in pairs, while the leaf-cells 
are considerably larger, averaging about 57 x 37 \i. 
Metzgeria fur cat a , (L.) Dumort. 
The gemmiparous material examined of this common and widely 
distributed species came from the following localities :—Zurich, Switzerland 
(Foerster); Cumberland, Maine (Chamberlain, No. 904); Jackson, New 
Hampshire (A. W. E.); Onteora Mountain, New York (Miss Yail, No. 26). 
The plants which develop the gemmae are usually more slender and less 
highly differentiated than normal plants. The hairs, for example, are less 
numerous and are sometimes absent altogether, the cortical cells along the 
postical surface of the costa are often reduced to two rows, while the 
elongated internal cells of the costa are reduced in number and sometimes 
not developed at all. The thallus, in other words, undergoes a reversion 
to a more or less juvenile condition, as Goebel (’98 b ) has already noted. 
The gemmae are borne without definite order, and the gemmiparous branch 
usually continues its growth for a considerable period. 
The early development of a gemma is similar to that just described 
for M. uncigera . One of the marginal cells projects in the same way, 
secretes a gelatinous substance on the inside of the pro¬ 
jecting wall, ruptures the outer wall, and then forms a thin 
new wall on the inner surface of the gelatinous layer. In 
contrast to M. uncigera , however, the projecting cell be¬ 
comes at once the mother-cell of the future gemma without 
undergoing a preliminary division. It proceeds to divide 
in the characteristic way, already described in detail by 
Naegeli (’ 45 ) and other observers. With regard to the 
separation of the gemmae at maturity, this is doubtless 
brought about in some instances by a rupture across the 
base, in the way described by Kny. But this method of 
separation is often premature and is apparently abnormal. 
In normal cases the basal cells simply split away from the 
adjacent thallus cells, and the process is unaccompanied by 
any destruction of tissue. The remains of the ruptured wall of the original 
projecting cell may often be distinguished after the gemma has been set 
free (Fig. 4). 
At the time of separation the gemmae vary greatly in length, but are 
usually more highly differentiated than in the other known members of the 
genus. They quickly form the beginnings of a costa, even the basal cells 
often dividing by walls parallel with the surface. The existence of dorsi- 
ventrality is also shown very early by the development of slime papillae on 
one surface of the gemma, the first papilla sometimes appearing only a few 
4'X # / *-*' f l' M'l' IV • XX. 
small gemma just 
separated from 
the parent thal¬ 
lus. x 80. 
