292 THE AMERICAN MONTHLY [Nov 
Fig. 19 represents a small portion of the Peltandra 
petiole in cross section. Fig. 20 is a view of one of the 
diaphragms enlarged 75 times. The cells show numer- 
ous grains of starch or chlorophyll. Richardia africana 
has the same structure as the Peltandra. 
The sheathing petioles of Canna indica have about 25 
air-passages arranged like those of the Musa. The dia- 
phragms are from three to six millimetres apart and are 
thickish and somewhat obliquely placed. The intermedi- 
t 
SS 
is 
tae . W/7 & Y 
ate chambers are filled with spongioid tissue, and this 
grows in close contact with the partitions so that it is 
very difficult to isolate them for examination. The dia- 
phragms themselves are of the Peltandra type. 
Some of the coarse grasses, like Zizania, have sheaths 
furnished like the Canna. Some have diaphragms with- 
out intermediate tissue. 
The leaves of Acorus calamus and the petioles of Sym- 
plocarpus fetidus have very numerous air-passages with 
ethmoid diaphragms. Very good examples have been 
i ir 
