280 Evans .— Vegetative Reproduction in Metzgeria. 
indications of dorsi-ventrality. The gemmae often give rise to secondary 
gemmae while still attached (Fig. 6 , b), and their method of separation 
from the parent plant is similar to that described for M. furcata. The 
germination of the gemmae has not been observed. 
Metzgeria oligotricha , sp. nov. 
The gemmae in this species are rather sparingly produced and are 
borne without definite sequence on normal vegetative branches. In the 
majority of cases their occurrence 
is intimately associated with the 
death of the apex of the branch, 
or else with the passage of the 
apical cell and the youngest seg¬ 
ments into permanent tissue ; 
under the latter circumstances the 
growth of the branch is limited 
even if its cells remain alive. 
Here again, as in M. furcata, the 
original marginal cell, which pro¬ 
jects, becomes at once the mother¬ 
cell of the gemma. The gemmae 
are exceeding variable, not only 
in size, but also in the degree of 
differentiation which they show, 
in the length of time during which 
their apical cells continue func¬ 
tional, and in the number of 
secondary gemmae which they 
produce. A typical gemma is a 
flat and broad thallus, abruptly 
broadening out from the two basal 
cells. It is about ten cells (or 
o*4 mm.) wide and usually from 
two to four times as long, and 
develops a variable number of long straight marginal hairs (Fig. 7). 
In some cases the hairs appear as mere rudiments and they may even be 
absent altogether. Although a gemma is usually but one cell thick, 
a rudimentary costa occasionally begins its development close to the base. 
The presence of such a costa, however, does not necessarily indicate 
dorsiventrality because it rarely develops either postical hairs or slime 
papillae. 
The germination of a gemma seems to follow a normal course under 
favourable circumstances. It gives rise at once to a thallus which gradually 
Fig. 7. M. oligotricha. A gemma about ready to 
separate, showing a secondary gemma at the left, 
x 80. 
