272 Evans .— Vegetative Reproduction in Metzgeria. 
Esenbeck (’ 38 , p. 488), who redescribed Hooker’s variety aeruginosa under 
the name M. furcata h gemmipara and called attention to the most striking 
peculiarities of the gemmiparous branches. He also described, as e prolifera 
and ( ulvula , forms of M. furcata in which the gemmae are marginal. 
A few years later Naegeli (’ 45 ) gave a full description of the way in which 
these marginal gemmae develop, and emphasized the fact that each one 
arises from a single cell. Further details were added by Hofmeister (’ 51 , 
p. 22) and by Kny (’ 64 , p. 7 6), the latter stating that the separation of the 
gemmae was brought about by the destruction of tissue. 
Up to this time the gemmae had been of interest more particularly to 
students of plant morphology; but Lindberg showed, in his Monographia 
Metzgeriae ( 77 ), that they deserved the attention of taxonomists as well. 
Unfortunately he failed to emphasize this fact very strongly, although he 
went far enough to refer different types of gemmae to definite species, and 
to imply by omission that they did not occur in the other species which 
he recognized. He stated that marginal gemmae occurred not only in 
M. furcata , but also in his newly described M. myriopoda , and that 
specialized gemmiparous branches were to be observed in M. conjugata, 
var. violacea , and M. furcata , var. fruticulosa, the latter being identical 
with Hooker’s variety aeruginosa. He also called attention, apparently 
for the first time, to those gemmae which arise on the surface of the wings, 
and noted their occurrence in M. Liebmanniana , M. dichotoma , M. crassi- 
pilis (published here as a sub-species of M. furcata ), and M. linearis. 
According to his statements gemmae of this character are always borne 
on the postical surface of the wings, but the writer has found them to 
be invariably antical in origin. Apparently, Lindberg’s mistake was due 
to the fact that gemmae, after becoming separated, often attach themselves 
to the postical surface of an overlying thallus and begin their germination 
in this position. 
Subsequent references to the gemmae of Metzgeria are very much 
scattered, but describe a few new observations of interest. Miss Boatman 
(’ 92 ), for example, notes the production of marginal gemmae in M. con¬ 
jugate2, while Schiffner (’ 00 , p. 60) and Pearson (’ 02 , p. 465) say that they 
are sometimes to be seen in M. hamata. Specialized gemmiparous branches 
have been studied by Ruge (’ 93 , p. 304) in an unnamed species from Ecuador, 
and by Goebel in the South American M. adscendens (’ 93 , p. 427), as well 
as in plants which he referred to M. conjugata (’98 a, p. 275). According to 
Ruge, the gemmiparous branches grow out from the antical surface of the 
costa, but Goebel states that they are simply the prolongations of ordinary 
branches of the thallus. Except for a short note by the writer (’ 09 , p. 189) 
on the antical gemmae of M. crassipilis , there are apparently no allusions 
to reproductive bodies of this type in the recent literature. Stephan i, in 
his revision of the genus (’ 99 ), makes no mention whatever of gemmae, and 
