IOWA ACADEMY OP SCIENCES. 
145 
There is more stereome above and below the secondary bun- 
dles, than in E. mexicana, and strong groups are found about 
the intermediate bundles. 
CONCLUSIONS. 
The results of this study are embodied in the analytical key 
which follows. The characters given will clearly separate the 
different species, though, with the exception of the peculiar 
glands of E. major ^ the differences between E. mexicana and E. 
major are not well marked. For instance, the number of cells 
of colorless parenchyma is constant in neither species, nor is 
there an absolute line of demarcation between these cells and 
the mesophyll. Again, while the carene bundle of E. mexicana 
is classed as an intermediate bundle, it will be noticed that the 
three large cells which form the superior part of the chloro- 
phyll-bearing parenchyma sheath resemble very closely, in 
their shape, cell- wall, and the almost entire absence of chloro- 
phyll, the adjacent cells of colorless parenchyma. 
In conclusion, the author wishes to acknowledge his obliga- 
tion to Prof. L. H. Pammel, under whose efficient direction the 
work has been done, for his invaluable assistance and advice; 
also to Miss Charlotte M. King, artist for the botanical depart- 
ment, for kind suggestions and assistance. Thanks are also 
due to Mr. P. R. Clements, of Lincoln, Neb., and Mr. W. D. 
Barnes, of Blue Grass, Iowa, who kindly furnished specimens 
for study. 
ANALYTICAL KEY. 
All mestome bundles provided with a chlorophyll-bearing parenchyma 
sheath; mestome sheath composed of a single row of cells radially arranged; 
stereome above and below all bundles. 
A. Superior epidermal cells of nearly equal size and all larger than the 
largest of the inferior epidermal cells; trichomes one-celled, long, 
slender, pointed. E. reptans. 
B. Superior epidermal cells unequal in size and not larger than the 
inferior cells; trichomes short and thick. 
I. Chlorophyll-bearing parenchyma sheath in bundles of secondary 
type (vein 3) distinctly pyramidal in outline, apex directed toward 
superior surface; lateral cells of sheath elongated transversely 
to the section. E. pectinacea. 
II. Chlorophyll-bearing parenchyma sheath in bundles of secondary 
type (vein 3) round or oval in outline, 
a. Carene not enlarged (or but little), especially on inferior side, not 
easily distinguishable from vein 2; trichomes equal in length to 
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