Il6 WHEAT STEMS 



The illustration (Fig. 33) is taken from a 

 photo-micrograph of 36 diameters. It was 

 done on a process plate owing to the section 

 being exceptionally weak. The time of ex- 

 posure was 3 minutes ; the focal distance was 

 36 inches, and the objective used was the 

 1-inch. 



It will be observed that this portion of the 

 stem is a hollow cylinder. The fact is that the 

 original central cellular tissue was torn up and 

 destroyed in the process of growth. Surround- 

 ing the central hollow is the cellular tissue, 

 while the dark patches are fibro-vascular 

 bundles. The outer dark margin consists of 

 closely-packed epidermal cells. 



In the next illustration (Fig. 34) we have 

 a section through one of the nodes. The 

 epidermal cells constitute, as in the previous 

 instance, the thin outer limits of the stem. 

 The wide band inside these limits is the sheath, 

 or base of the leaf, containing fibro-vascular 

 bundles in the midst of cellular tissue. 



Further in we have the stem within the leaf, 

 also with fibro-vascular bundles. The central 



