18 



BULLIFORM CELLS. 



been called hygroscopic 

 cells. They are usually 

 more or less wedge-shap- 

 ed, with the point of the 

 wedge towards the out- 

 side of the lea*. In Zea 

 mays (Indian corn) 

 these cells are raised 



FIG. 20. This illustrates the cross section at the , 



margin of a leaf of Amphicarjmm Purshii, shown in above the other ceils 

 three places, at o, there is a growth of peculiar cells 



surrounding the base of a hair, at ft, we have another anc [ p u g ou t }ik e a 

 view, and at c, where no hair is seen, the large group 

 of hypodermal fibers is covered by an ordinary epi- i i > nv 

 dennis. 1 x 40.-(Sudworth.) blister. 



When viewed on the surface of 

 the leaf, the bulliform cells are 

 usually seen to have the propor- 

 tions of length and width much 



some 



FIG 21. A portion of a cross-section , ,, , ., 



of a leaf of Zea mays, showing one cases these cells are as long as wide, 



band of bulliform cells raised above 



the surface, i x i7.-(Sudworth.) w jth outlines somewhat wavy. 



The number of rows in a species is always the same, but varies 

 with the species from 3-12 in a band. If there are many rows, 

 the cells are shallow ; if few rows, the cells are deep ; if three 

 only, those at the side are small, and the middle one is very large. 

 The arrangement of these cells is invariable in a species, but in 

 a genus they vary much. The following examples are given : 



^^^ ^_ 



like those next to then , In 



FIG. 23. Cross-section of a leaf of Ownodon Dactyton, showing a very large bullifo 

 cell, with one or two small ones on each side of it. 1 x 130. (Sudworth). 



