ANATOMY OF SOME PLANTS OF A PROVINCE IN IOWA 83 
basin than in the upland prairie. Among the contributions deaHng with Iowa 
grasses are the following: Emma Pammel Hansen (12) studied the anatomy 
of Lolium perenne, Festuca elatior, F. tenella, and Bromiis patulus. Emma 
Sirrine (17) described and illustrated the anatomy of Bromus patulus, B, 
inermis, and B. secalmus. Pammel and Sirrine (13) investigated the anat- 
omy of Sporoholus heferolepis, S. cryptandrus, S. Hookeri, S. vaginaeflorus , 
Panicum capillare, P. proliferum, and P. crusgalli. These investigators 
call attention to the difference in anatomy of plants growing in dry and in 
humid environments. C. R. Ball (2) examined Eragrostis reptans, E. 
pectinacea, E. Purshii, E. Frankii, E. Mexicana, and E. major, and describes 
the epidermal cells of E. pectinacea as having thicker walls than those of 
E. Purshii, the latter being adapted to dry and sandy soil. C. B. Weaver 
(21) worked upon the anatomy of Andropogon nutans, A. scoparius, A. 
sorghum, and A. sorghum var. halepense. Miss Pammel's studies of Bromus 
show little development of buUiform cells and a homogeneous mesophyll, 
in contrast with the prominent bulliform cells of reduced spongy paren- 
chyma and the radial palisade of Weaver's Andropogon and Ball's Erag- 
rostis, both species of dry habitats. Theo. Holm (8) has studied the 
species of the genera Uniola, Distichlis, Pleuropogon and Leersia. Pammel, 
Weems, and Lamson-Scribner (11) have called attention not only to the 
use of anatomical characters of grasses for systematic distinction but to 
such structures as related to habitat. An interpretation of the above cited 
morphological facts concerning a number of species of a genus and a com- 
parison of genera with a knowledge of the habitats of these plants would 
leave no doubt as to the adaptation of species of this family to their habitats. 
In general, the anatomy of these leaves of prairie plants resembles that 
of the plants described in Harshberger's (7) pine barren studies in their 
development of epidermis and mesophyll features. 
Ella Shimek (16) has described plants of Iowa prairies with some 
illustrations of leaf characters, in which the leaf structure coincides with 
the anatomical observations of the present study. 
Summary 
The leaves of prairie plants show a xerophytic tendency in their leaf 
structure, indicated by the specialized palisade tissue, the thick-walled and 
trichomeless epidermis, the presence of water-storing tissue, and sometimes 
of trichomes. 
The mere presence of these characters is not of primary significance as 
an indication of xerophytism, but their relative development correlated 
with other morphological features of the plant such as the extensiveness of 
the root system. 
The upland plants have a thinner epidermis than those of the lowland, 
and 70 percent of those studied are without trichomes while 75 percent of 
the upland species have trichomes. 
