326 BOTANICAL GAZETTE [MAY 
shows one layer of typical palisades above a pneumatic tissue of 
roundish to more or less oblong cells with wide intercellular spaces. 
However, the stratum of pneumatic tissue which borders on the dorsal 
epidermis is in some places developed almost as palisades, the cells 
being more regularly oblong and more compact; as will be shown 
later, a palisade tissue is very typically represented on both sides of 
the dorsal keel of the midrib. No crystals were observed in the 
mesophyll, but long fusiform cystoliths are frequent in the epidermis, 
especially on the dorsal face. 
Collenchyma and stereome seem to be entirely absent from the 
lateral portion of the blade, and thus the lateral veins are directly 
imbedded in the chlorenchyma. They are very fine, orbicular in 
cross-section, and surrounded by a thin-walled, colorless parenchyma 
sheath. 
A more complicated structure is to be found in the median portion 
of the blade with the strong midrib. Near this part of the blade the 
leaf is thicker, due to an increase in height of the palisade tissue, 
while in the midrib a prominent broad and very obtuse keel is to be 
observed on the dorsal face, and a similar, though much less pro- 
jecting one, on the ventral. The epidermis is very small-celled in this 
part of the blade and covers a broad strand of thick-walled collen- 
chyma in about three layers on the dorsal face. There is also collen- 
chyma on the ventral face, and this is extremely thick-walled and 
represented either by two separate strands near the middle, or by a 
single one exactly above the center of the midrib. A large, thin- 
walled colorless tissue occupies the greater portion of the keel, but 
occurs also above the mestome bundles which compose the midrib. 
The chlorenchyma is on faces of the midrib interrupted by the collen- 
chyma; it occurs as two strata of high palisades on the ventral face, 
and as one or two strata of lower palisades (fig. 23) in the sides of the 
keel; thus, as stated above, this tissue is not confined to the ventral 
part of the bladealone. The pneumatic tissue is also well developed, 
but only near the dorsal keel. There are three mestome bundles in 
the midrib; one very broad, in transverse section crescent-shaped 
with the concave face turned upward, and two very small lateral 
ones, orbicular in cross-section. A thin-walled endodermis covers 
the leptome side of these three mestome strands, but not the hadrome. 
