328 BOTANICAL GAZETTE | [NOVEMBER 
species. The thickening may be observed in the cells of the 
stems and branches, but is best studied in the leaves. Here it is 
most pronounced in the angles of the cells, where it forms dis- 
tinct and often conspicuous trigones, but it affects the cuticle of 
the leaves as well. In this region the thickening is fairly uni- 
form, and we sometimes find a uniform thickening also in the 
vertical walls of the marginal cells. Intermediate thickenings 
seem never to be present. 
In O. Macounit the thickenings of the cell wall are especially 
pronounced, the trigones being extremely large, and the cuticle 
thickened in a corresponding degree (figs. 5,6). The trigones, in 
fact, project far out into the cell cavities, which become in con- 
sequence distinctly stellate with narrow rays, the latter of course 
forming pits for communication between adjoining cells. It 
is often possible to recognize in a trigone a distinct line of demar- 
cation separating the original trigone, as laid down in the devel- 
oping leaf, from a secondary deposit. This line of demarcation 
is clearly brought out by treatment with sulfuric acid in the 
presence of iodin, which serves at the same time to demonstrate 
the presence of cellulose in the wall. The trigones of this species 
are especially likely to be confluent; in some cases this is true of 
the original trigones; in other cases the coalescence is brought 
about by the secondary deposit, which causes at the same time 
the obliteration of a pit. Much of the thickening of the cuticle 
is also due to the secondary deposit. The cells of the under- 
leaves are sometimes rather thin-walled, and sometimes have 
thicker walls than the leaves themselves (fig. 73). The last is 
true also of the leaves on gemmiparous branches, of the peri- 
gonial and perichaetial bracts, and of the lower part of the peri- 
anth (jig. 23). In most of these regions there is a tendency for 
the cells to be arranged in longitudinal rows, and the excessive 
thickening brings about an extensive coalescence of trigones. 
These are commonly united in such a way that the pits connect- 
ing the cells laterally are filled up by the secondary deposit, 
while those connecting the cells longitudinally are retained. 
Through this process the lower part of the perianth becomes a 
series of flattened thick-walled tubes, which are continuous except 
* ae 
