268 KANSAS UNIVERSITY SCIENCE BULLETIN. 



0.0027 millimeters thick and the lower averages 0.0041 milli- 

 meters thick. 



The chief part of the internal tissue of the leaf is composed 

 of aqueous or thin-walled parenchymatous tissue. This tissue 

 encloses the median vein, together with its branches, lying 

 immediately below the short chloroplast-bearing cells. The 

 lumen of the aqueous tissue cells averages 0.2437 millimeters 

 longitudinally and 0.0875 millimeters radially. The walls are 

 0.0058 millimeters thick. These cells have a few chloroplasts 

 (fig. 29), and frequently calcium oxalate crystals. Their fre- 

 quency is shown in figure 22. 



Figure 30 shows the leaf in cross section. Figure 34 shows 

 the details of the median vein in cross section, and figure 26 

 a part of the same in longitudinal section. The water-conduct- 

 ing tissue consists of trachese averaging 0.00875 millimeters in 

 width, with annular thickenings. The phloem parenchyma and 

 undivided mother cells have walls averaging 0.00134 millime- 

 ters in thickness. 



On the upper side of the leaf, from its connection to the 

 stem, extending about one-third of the length of the leaf, is a 

 depression (a, fig. 30). Below this the cylinders of palisade 

 parenchyma and short chloroplast-bearing cells are broken, 

 and through the gap the aqueous tissue extends to the epider- 

 mis, the cells of which in this region are elongated parallel 

 with the long axis of the leaf (a, fig. 24). 



On the under side of the leaf, near the tip, the palisade pa- 

 renchyma cylinder and the cylinder composed of short chlo- 

 roplast-bearing cells are again broken. Beneath the epider- 

 mis, which in this region has elongated cells, are lignified bast 

 fibers. As the tip is neared, more of the leaf is devoted to 

 these bast fibers, until the median vein is entirely surrounded 

 by bast fibers. This forms the spine. Figure 31 is a cross 

 section near the tip of the leaf, and figure 32 a cross section 

 through the spine. Figures 30, 31 and 32 are all drawn to the 

 same scale, so that the decrease in diameter as the leaf nar- 

 rows into the spine is shown. Figure 25 shows the tip of the 

 leaf longitudinally. The spine averages 1.3 millimeters long 

 and 0.225 millimeters wide. The bast fibers average 0.26 

 millimeters long and have walls 0.005 millimeters thick. 



The following list of the families having an anomalous stem 



