200 KANSAS UNIVERSITY SCIENCE BULLETIN. 



found ; 20 per cent of the vascular bundle is devoted to phloem, 

 as in Townsendia. Neither seive tubes nor seive parenchyma 

 cells are found. The whole work of conduction is assumed by 

 the undivided mother cells of the sieve tubes. Lesquerella is 

 a very low plant and it seems that the food can be conducted 

 longitudinally fast enough and in sufficient quantities without 

 the aid of the other phloem elements. In figure 51, c, are 

 shown a few phloem cells as seen in cross section ; in figure 52, 

 as seen in longitudinal section; at the angles of these cells 

 occur small intercellular spaces, A. 



In the stem of Lesquerella the storage of food is provided for 

 by means of the thin-walled parenchyma of the cortex and the 

 xylem parenchyma and the medullary rays. Figure 53 repre- 

 sents a few cells of the thin-walled parenchyma of the cortex 

 as seen in cross section. Figure 54 represents a few cells of the 

 xylem parenchyma as seen in longitudinal section. In all of 

 these tissues starch and proteid were found in small quantities, 

 but neither sugar nor oil. 



Figure 50 is a diagrammatic drawing of the cross section of 

 the stem traced as seen when projected upon a screen. From 

 this may be derived a general idea of the various tissues of the 

 stem, their relation to one another, and the proportion of the 

 stem devoted to each: A, borke; B, collenchyma; C, scleren- 

 chyma; D, phloem; E, xylem; 1, tracheal tissues; 2, wood 

 fibers ; 3, xylem parenchyma ; F, medullary ray ; a, leaf -trace. 

 The Root. 



The Tegumentary Tissues. — The tegumentary tissues of the 

 mature root consist of a cutinized epidermis and cork tissue 

 which are similar to those tissues found in the stem, both in 

 structure and proportion. 



The Strengthening Tissues. — The strengthening tissues 

 found in the root of Lesquerella consist of collenchyma, stone 

 cells and wood fibers. These tissues show no difference what- 

 ever from those found in the stem. 



The Tracheal Tissues. — The tracheal tissues in the root con- 

 sist entirely of scalariform and spiral tracheal tubes. In a 

 root where the cross section area was 18.75 sq. mm., there was 

 found devoted to the conduction of water 4 per cent. Here the 

 cross-section area of the xylem is 6.7 per cent of the entire 

 root. 



In the following table is given the average diameter and the 



