MacMillan: OBSERVATIONS ON PTERYGOPHORA. 737 
with smaller. Outside of the rings will be found the cambial 
zone in which regular divisions take place in all three planes of 
space. Exterior to the cambial zone lies a thin outer cortex 
composed of cells very much smaller than those of the inner 
area, provided with thick walls and constituting a kind of bark 
for the trunk. In some material the general cambial zone can 
be very distinctly seen, ten or twelve cells in thickness and 
separated from the epidermis by twenty or more layers. Not 
infrequently the cells at the periphery of a ring of growth have 
more densely granular contents than those of the general sec- 
ondary cortex tissue. Thus, occasionally in the stipe there may 
arise the anatomical conditions which seem to be more normally 
characteristic of the holdfast. The photographs of different 
cross and longitudinal sections which are presented will serve 
to make these points clear where the description is necessarily 
difficult to follow. 
The /amina.—As before stated only the central lamina is pro- 
vided with a midrib, the pinne being quite devoid of such a 
structure. The midrib of the central lamina arises through an 
hypertrophy of the cortical tissue, in which th: pith-plate does 
not seem to partake. The general structure of the lamina as 
seen in cross section does not present many peculiar features, 
but is much like that already described for other genera. There 
is on each surface an isomorphic epidermis composed of small 
quadrate chlorophyll-containing cells, and these merge insensi- 
bly into the subepidermal tissue, which in some instances is 
two or more layers in depth. The cells then become much 
larger in diameter and the contents less dense. Among these 
cortical cells occasional very large polysaccharid idioblasts are 
found, and in the chocolate-colored pinnz of plant ‘* C,” these 
cells are very numerous and densely packed with spherical 
bodies, doubtless belonging to the category of reserve carbohy- 
drates. Owing to the nutritious character of such pinnae, they 
are very commonly perforated by animals, sometimes giving a 
colander appearance like that of Agarum, and covered with 
epiphytic and endophytic vegetation, a further study of which 
should be made. These reservoir cells may perhaps be packed 
with food materials previous to the production of sori and the 
polysaccharids utilized in the elaboration of the sporangia and 
paraphyses. In any event they seem to be emptied of their 
contents underneath most of the soral areas that I have exam- 
