Vegetative Production of Flattened Protonema. 47 
of leaves containing gemmae and were quite normal. In a consi¬ 
derable number, however, the apex of the stem had ceased to grow, 
and the stem ended abruptly in dead, brown cells. These plants 
had leaves of the ordinary Tetrapliis type, which decreased in size 
downwards until at the base of the stem they were rudimentary and 
scale-like in character. But the most noticeable feature about 
these plants was the occurrence in the axils of many of the leaves 
(usually the upper leaves) of large thalloid outgrowths (Fig. 1* a). 
These outgrowths are flat expansions, one cell thick, deep-green 
in colour, and of a spathulate form, with a narrow, tapering basal 
part, and a wide, rounded apex. They resemble in every respect 
the thalloid protonemata which are so characteristic of Tetrapliis, and 
they are undoubtedly of this nature. As many as five of these out¬ 
growths, of various ages, may occur on a single stem, but the average 
number is about three. In size they are anything up to 2 mm. long, 
and 1 mm. broad at their widest part, thus being considerably 
larger than the largest Tetraphis leaf. They arise in the first place 
as narrow tongue-like green outgrowths from the stem, immediately 
above the insertion of a leaf, but not quite in its axil. Fig. 1, a, 
shows three of these thalloid protonemata (the lowest one, a, being 
the youngest) on a leafy stem. The early stages in their develop¬ 
ment are shown diagrammatically in Fig. 1, e to g. They arise by 
the outgrowth of a single superficial cell of the stem, and are thus 
always fixed to the stem by a single connecting cell. Their cells 
from the earliest beginning are packed with chloroplasts and also 
contain abundant starch. 
It is well known that similar thalloid protonemata are developed 
from the gemmae (as well as from the spores) of Tetraphis on germi¬ 
nation. Fig. 1, b, shows a gemma (g) germinating and developing 
one of these expansions (/>). In no case could the protonemata 
growing on the stem be seen to be in connection with any gemma 
or spore. 
When these thalloid expansions (growing from the stem) have 
reached a fairly large size one or more filamentous, colourless or 
brownish, rhizoidsgrow out from their narrow basal part (Fig. 1, a, c). 
These rhizoids usually become closely appressed to the stem down 
which they grow. They are of the ordinary moss type, with oblique 
cross-walls. The extreme basal cells of the protonema, where it is 
joined to the stem, are brownish in colour, and by the disorganisation 
of these cells the mature protonema can be readily be detached 
from the stem. It leaves a distinct scar on the stem at the point 
