296 Evans .— Vegetative Reproduction in Metzgeria. 
axis acquires the form and structure of the specialized gemmiparous 
branches described above. Except under the last conditions the new 
gemmae are always marginal and show no peculiar features. 
It follows from the above description that the development of gemmae 
in M. fruticulosa is often associated with a more or less incomplete 
differentiation of the gemmiparous plant; in other words, that the growth of 
the plant is concluded while it is still in an embryonic or juvenile condition. 
Even the prostrate thallus, which has been spoken of as normal, presents 
certain juvenile features, and apparently never reaches the stage of develop¬ 
ment in which sexual branches can be produced. These facts naturally bring 
the validity of the plant, as a species, into question, and it seems possible 
that it may simply represent an immature stage of some other member of 
the genus. If the known range of M. fruticulosa is taken into considera¬ 
tion, it will be seen that three other species, M. pubescens, M. furcata, and 
M. conjugata , have a very similar distribution. With the very distinct 
M. pubescens it can hardly have any close connexion, but with the other 
two species it shares numerous characters in common. In M. furcata, 
var. ulvula , however, another plant is met with in which the thallus usually 
fails to develop beyond a certain stage. Since this variety ulvida is 
entirely different from M. fruticulosa in appearance and method of growth, 
it is scarcely probable that they can both represent juvenile conditions of 
the same species. The fact that the marginal hairs are not displaced, and 
that they are occasionally geminate, indicates an approach to M. conjugata^ 
but its identity with this species could only be proved by culture experi¬ 
ments. It should be noted, however, that the gemmiparous plants which 
Goebel (’ 98 #, p. 275) refers to M. conjugata are apparently what is here 
described as M. fruticidosa , but Goebel does not state that he demonstrated 
the connexion between his plants and undoubted M. conjugata. Until this 
is done it seems allowable to keep the two species distinct. If it becomes 
necessary to unite them in the future the plant should still bear the name 
fruticulosa , since this has a priority of over eighty years. The history of 
M. fruticidosa and the various views which writers have held concerning 
it are clearly shown by the following synonymy, taken mostly from 
Lindberg’s Monograph:— 
Metzgeria fruticulosa, (Dicks.) comb. nov. 
Riccia fruticulosa , Dicks., PI. Crypt. Brit., i, 8. T785. 
Jungermannia fruticulosa Smith, Engl. Bot., xxxv, pi. 2514. 1813. 
Jungermannia fur cat a, var. aeruginosa, Hook., Brit. Jung., pi. 55. 
1816. 
Fasciola violacea , Dumort., Comm. Bot., 114. 1822 (not Junger¬ 
mannia violacea , Ach.). 
Echinogyna violacea , Dumort., Syll. Jung. Eur., 84. 1831. 
