104 THE UNIVERSITY SCIENCE BULLETIN. 



Many clothing hairs (fig. 77) and a few glandular hairs (fig. 78) 

 can be found on the young leaves, but only a few hairs are present 

 on older leaves. Most of the hairs are located at the edge of the 

 leaf, but on young leaves quite a number are scattered over the 

 upper and lower surfaces. 



Each clothing hair is seated on a prominent basal cell, above 

 which it consists of a chain of one or more short cells (fig. 77, a"), 

 distinguishable by a very thin cuticle from a long terminal portion 

 of one or several cells (fig. 77, u') having thin cellulose walls with- 

 out cuticle. 



The glandular hair has a basal portion made up of a chain of 

 two or more cells with a very thin cuticle (fig. 78, a"), and a ter- 

 minal portion consisting of a row of three or more cells, usually 

 all but the end cell being conspicuous on account of cell contents 

 and a thin cuticle. Cell contents are present in the large spherical 

 or ovoid terminal cell of certain of these hairs (fig. 78, h'). The 

 wall of this terminal cell stains blue in chloroiodide of zinc, and 

 does not stain appreciably in Phloroglucin or Sudan III. The 

 contents of the hair cells is discussed in the section on the nature 

 of cell contents. 



There are two types of hairs on the stem similar to the hairs on 

 the leaf. A clothing hair of the stem is shown in fig. 16, and a 

 glandular hair is shown in fig. 17. 



The stomata are of ordinary type (figs. 74, 75 and 76). Sole- 

 reder ('08) gives the absence of a definite type of stoma as a 

 noteworthy feature in the leaf of the Chenopodiese. The cuticle 

 extends over the guard cells (fig. 73, /")• The stomata are almost 

 as numerous in the upper epidermis as in the lower epidermis of 

 the leaf, there being 122 stomata per sq. mm. in the upper epider- 

 mis, and 128 p)er sq. mm. in the lower. Usually the long axes of 

 the stomata, as seen in surface view, are placed at an angle with 

 the main rib of the leaf, although many are parallel with the main 

 rib in both young and old leaves. The transverse arrangement of 

 the stomata is not uncommonly shown by narrow leaves in the 

 Chenopodieae, but also occurs on the stem, according to Solereder 

 ('08). 



The mesophyll of the leaf is approximately 65 per cent photo- 

 synthetic tissue and 35 per cent water-storage tissue (figs. 71, c 

 and d; 72, c and d; and 73, c and d). Solereder mentions the dif- 

 ferentiation of the mesophyll into assimilatory and aqueous tissue 

 as one of the leaf characters of the Chenopodiaceae correlated with 

 their dry-land habitat. 



