204 KANSAS UNIVERSITY SCIENCE BULLETIN. 



27 : 1000. On either side of the leaf are found 640 stomata to 

 1 sq. mm., a much larger number than was found in the leaf 

 of Townsendia. The stomata are at the surface of the leaf in- 

 stead of being sunken, as is often the case with xerophytes. 

 In figure 67 are shown a few stomata as seen in surface view. 

 In figure 68 is shown a stoma as seen in cross section. 



Figure 69 represents a small portion of a leaf as seen in 

 cross section: A, upper epidermis; B, lower epidermis; C, 

 palisade tissue ; D, vascular bundle. 



SUMMARY. 



1. Size and Habit of Lesquei'ella spathulata. — Lesquerella 

 spathulata, a perennial from a branched caudex, is a low plant 

 growing from one to two inches high. It was found growing 

 on a rocky clay bluff, occurring not as isolated individuals, but 

 in colonies. 



2. Tegumentary Tissues. — In the mature stem of Lesque- 

 rella the tegumentary tissues consist of a cutinized epidermis, 

 cork, and borke. In the mature root the tegumentary tissues 

 consist of a cutinized epidermis and cork. 



The tegumentary tissues of the leaf consist of an epidermis, 

 all the walls of which are cellulose except a thin film of cutin 

 on the outer tangential wall. There is, in addition to the ordi- 

 nary epidermal cells, stellate trichomes on both sides of the 

 leaf, which would be effective in protection against too intense 

 illumination and in the reduction of transpiration, as well as 

 in the storage of water. 



3. The Strengthening Tissues. — The strengthening tissues 

 consist of collenchyma, bast fibers, stone cells and wood fibers. 

 The wood fibers constitute a very important part of the 

 strengthening system. These have remarkably thickened 

 walls, the cavities in some cases being almost obliterated. 

 Contrary to the general rule, the wood fibers are found among 

 spiral tracheal tubes, both wood fibers and spiral tracheal 

 tubes having been formed by the cambium. 



4. Tracheal Tissues. — The tissues devoted to the conduction 

 of water constitute 2 per cent of the stem and 4 per cent of the 

 root. This seems a comparatively small area devoted to this 

 purpose, but growing, as Lesquerella does, in a location where 

 the water supply is poor, it would not require very extensive 



