ECOLOGICAL HISTOLOGY OF PRAIRIE PLANTS 
121 
THE ECOLOGICAL HISTOLOGY OP PRAIRIE PLANTS. 
. ELLA SHIMEK. 
The investigation, the result of a part of which is here pre- 
sented, was made for the purpose of ascertaining the character 
of the various structural adaptations to environment which ap- 
pear in the ordinary plants of our Iowa prairies. Of the 271 
characteristic species of our prairies 65, representing a wide 
range of families and genera, were selected for these studies. 
The material for this purpose was collected on the dry prairie 
ridges or bluffs in Harrison county, and on the less rugged prai- 
rie in the vicinity of the Okoboji lakes, and at Iowa City. 
The limits of this paper do not permit a full presentation of 
the results of the work, but a few illustrations are given to show 
the chief characters which mark the flora of the prairie as es- 
sentially xerophytic. 
The plants of the prairies usually show a reduced leaf sur- 
face, a large root system, a hairy or pubescent surface, or if 
smooth then leathery, and not infrequently may form rosettes 
for better protection. In short they present all the grosser 
structural adaptations which are usually recognized as char- 
acterizing xerophytes. 
The microscopic structure, especially that of the leaves, also 
shows xerophytic adaptations, developed in various degrees. 
Frequently the impervious cutin is thick, as shown in figures 
1 and 5, Plate XX ; sometimes the stomatal guard cells are sunken 
in pits, as is shown in figures 1 and 2; the leaf parenchyma 
usually is very compact, while the intercellular spaces' are very 
small ; and various water-storage cells are developed. 
The water storage tissues are usually of two types. The one 
consists of the bulliform cells of Duval-Joune, which form a part 
of the epidermis, as is shown in figure 8. The other is a chloro- 
phyll ess parenchyma which usually surrounds the vascular 
bundles, as shown in figure 3, and which is known as border 
parenchyma. This sometimes extends in the form of a plate 
parallel to the two leaf surfaces, as is shown in figures 5 and 6 ; 
or it forms vertical plates or columns, as is shown in figures 4 
