42 Farmer. — Studies in Hepaticae : 
prosenchymatous pitted cells of the branch never unites with 
that of the mother-axis, but it ends blindly in the base of the 
branch. The cells in this region are short, and their cavities 
are large, and this is of course due to the fact that at this 
early period, the longitudinal divisions which cause the fibres 
to be so narrow in the more developed parts of the branch, 
were much less frequent at the time of its incipient growth, 
while at the same time transverse divisions were much more 
abundant than is subsequently the case. 
A biological result of this lack of union is seen in the 
relative independence of the daughter-axes and the ease with 
which they become severed from the mother-shoot, to form 
fresh plants. 
Structure of the Fronds . — The ‘ frond ’ is formed, as has 
already been stated, by rapidly succeeding dichotomy 
accompanied by a development of the thallus-wings, which 
are suppressed on the creeping portions of the plant. The 
apex exhibits the same structure as in the subterranean 
parts, though it is more difficult to determine its structure 
here. The actual apical cell lies at the base of a sinus, 
caused by the rapid growth of the segments, and it is 
bathed in the mucilage poured out by the hairs formed 
for this purpose. The fresh apices which arise as the 
result of the pseudo-dichotomy in the frond do not behave 
like those of the creeping stems ; on the contrary they 
develop immediately, and thus the mid-ribs of the different 
axes are not here disconnected, but form a forked system 
corresponding to the branches of the frond. The edges of the 
lamina are toothed, and these teeth are situated as filiform hairs 
on a multicellular base, but they do not appear to be formed 
in a definite manner from the segments. The occurrence of 
adventitious ventral shoots on the fronds has already been 
alluded to. They may have been formed near the apex of the 
frond, but I do not think this is the case. Moreover, the 
structure of their apical cells is different from that of growing 
axes, since they always exhibit a triangular outline in longi- 
tudinal sections of the frond (PI. VI, Fig. 12), and this probably 
