HOP-PICKERS OPHTHALMIA. 



277 



coarser than those upon the leaves and bracts. These sharply- 

 pointed processes are scattered all over the surface of the bracts, 

 with the apices of each spine directed towards the distal end of 

 the bract as regards its point of attachment to the pedicel. The 

 spines on the leaves are confined more to the edges, and do not 

 appear to be so hard and dense and sharp as those upon the 

 bracts. In Fig. 70 some of the characteristics of these spinous 

 processes are shown. 



Fig. 69. — Spine-shaped hairs of the hop-bracts, a, Entire spinous process ; 

 b, fractured ; t, showing hollow central canal (transverse section). 



In staining with various dyes, the outer portion of the hair 

 accepts the staining re-agents less readily than the softer internal 

 parts. When for any reason they are fractured between the 

 facetted point of attachment to the bract and their pointed 

 extremity, the fractured ends are not unlike those of a mature 

 bone or a dry branch of a tree, with a less dense central portion. 

 The bracts are also covered with glandular structures and lupulinic 

 grains. Emphasis is placed on the fact that these hairs are denser 



