COLLECTING ECONOMIC PLANT DATA 



45 



plant that has been dead the longest, rather than in newly infected 

 portions, that is, in dead shriveled leaves rather than in recently wilted 

 ones; in blighted leaves that have fallen; in larger, decayed spots, in- 

 stead of the smaller ones (fig. 30, E) : and on the inner and older portion 

 of a canker but not on the advancing edge. Leaf rusts and mildews 



Figure 30. — Various examples of diseased plants. A, Bracket fungus attached to a 

 piece of rotted wood (greatly reduced); B, smut of bamboo flowers; C, stem canker, 

 young and old stages; D, stem gall; E, fruit rot; older stage at right shows minute dots 

 which are the fruiting structures of the fungus. 



occur usually on the under-leaf surface, and at times may be obvious 

 from above only by a slight discoloration or yellowing, or perhaps 

 merely by a slight distortion or crinkling of the leaf. 



Workers in tropical countries will frequently encounter various kinds 

 of insects which have been parasitized and killed by fungi (fig. 33). 

 These interesting specimens should always be collected. They require 

 drying over a gentle heat and then are packed in small tin salve boxes, 



