142 
IOWA ACADEMY OP SCIENCES. 
Mestome bundles . — The mestome bundles are thirty -five in 
number, representing all three types. Of the primary type 
(vein 2) there are four bundles, in which the leptome, hadrome 
and thick-walled parenchyma are well developed. These veins 
(vein 2) are enlarged on the superior face but not on the infer- 
ior face. The chlorophyll-bearing parenchyma sheath consists 
of four or five cells on each side of the bundle, being interrupted 
below by stereome and above by a few cells of thick- walled 
parenchyma. 
There are thirty secondary bundles (vein 3) containing normal 
leptome, hadrome and thick- walled parenchyma. The chloro- 
phyll-bearing parenchyma sheath is subpyramidal in outline 
and composed of five to seven large, subcircular cells with two 
smaller cells below. The intermediate type is found only in the 
carene and is open below. Leptome, hadrome and thick- walled 
parenchyma are strongly developed, the latter passing down to 
the side of the leptome, which is surrounded by stereome. 
The mestome sheath is continuous above the secondary 
bundles, but above the primary bundles it is interrupted by 
stereome and above the intermediate bundles by colorless paren- 
chyma. 
' Carene . — The carene, already discussed as the intermediate 
bundle, is much enlarged on the inferior side and somewhat so 
on the superior side. It contains much mesophyll and stereome 
and some colorless parenchyma. 
Stereome occurs in small quantities both above and below the 
primary and secondary bundles and in much larger quantity in 
the carene. Directly beneath the center of the carene the 
stereome is normal in appearance (at x pi. xvii, Fig. 12a) but 
on either flank it is curiously modified (z pi. xvii, Fig. 12a.) 
The cell wall is much thinner and does not have the strong 
greenish yellow color of the normal cell wall. The inner por- 
tion of the cell is dark colored and in the very center is a small 
black dot or cavity. This modified stereome is also found in 
the same part of the carene of E. mexicana and E. major. Stere- 
ome also surrounds the leptome in primary and intermediate 
bundles. 
Mesophyll is abundant in the enlarged carene and normal 
elsewhere in the leaf. Four or five cells of colorless paren- 
chyma are found in the carene between the stereome and the 
chlorophyll-bearing parenchyma sheath. 
