18 



BULLIFORM CELLS. 



Fig. 30.— This illustrates the cross section at the , 



margin of a leaf of Arnphicarpum Pvrtfhii, shown in abOVe 

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



surrounding the base of a hair, at h, we have another aud puff 



been called hygroscopic 

 cells. They are usually 

 more or less wedge-shap- 

 ed, with the point of the 

 wedge towards the out- 

 side of thelea^'. In Zea 

 mays (Indian corn) 

 these cells are raised 

 the other cells 

 out like a 



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



of hypodermal fibers is covered by an ordinary epi- i^i:,j-^,. 



dermis. 1 x40.— (Sudworth.) Dllbtei. 



When viewed on the surface of 

 the leaf, the bulliform cells are 

 usually seen to have the propor- 

 tions of lengtli and width much 

 like those next to them. In 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 huUiform cells raised above 



the surface. 1 x i7.-(Sudworth.) with Outlines somewliat 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 : 



Fig. 22.— Cross-section of a leaf of Cynodon Dactylon, showing a very large bulliform 

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



