148 
ALEXANDER W. EVANS 
less convex. At the apex of the branch the few leaves which are 
still attached bend backward almost as strongly as the underleaves. 
After the leaves have fallen away the surface of the branch appears 
irregularly roughened from projecting cells, but it is difficult to deter- 
mine the actual lines of attachment. The upright leafless branches, 
with their persistent and crowded underleaves, present a very dis- 
tinctive appearance. Aside from P. torulosus branches of this char- 
acter have not been noted in the Lejeuneae Holostipae. They may 
be compared with the flagelliform branches found in FruUania Bo- 
landeri and in the two species of Rectolejeunea noted above. 
The behavior of the caducous leaves after they have fallen away 
was observed in but a single instance. In this case a new shoot 
had grown out from the lower surface of the lobule not far from the 
apical tooth. This shoot was leafy from the very base and had im- 
mediately formed undivided underleaves as well as leaves. The 
latter, although small, showed distinct lobules. In the few Lejeuneae 
where germination has been observed the spore first gives rise to a 
row of cells (sometimes very short), then to a flat thallus and finally 
to a leafy shoot. In certain other genera the leafy shoot at its be- 
ginning is destitute of underleaves and shows undivided leaves, even 
though the adult shoot bears well-developed underleaves and bilobed 
leaves. It is of interest to note that the shoot growing out of the 
caducous leaf in P. heterophyllus showed none of these embryonic 
features. At the same time it would be premature to draw any 
general conclusions from a single example, and it is probable that cases 
of more pronounced reversion may yet be discovered. It is also 
probable that the new shoots do not always arise from the lobule. In 
Rectolejeunea flagelliformis , where the caducous leaves lack lobules, 
the new shoots grow out from the margin of the lobes, and it would be 
natural to suppose that the Ptychocoleus might show the same phe- 
nomenon. 
The lobular teeth in P. heterophyllus are usually five to seven and 
are remarkable for their uniform structure and regular spacing. On 
account of their being so strongly inflexed it is easy to overlook them, 
and their features can only be made out satisfactorily by careful dis- 
section. Each tooth consists of a single projecting cell borne on a 
broader basal cell, and the apical tooth is indistinguishable from the 
others except by its position. The proximal tooth, however, is often 
less«definite. The apical sinus, in explanate lobules, continues the 
