COLLECTING ECONOMIC PLANT DATA 



47 



pressed flat for drying. In some fruit rots the diseased areas appear as 

 circular soots of variable size (fig. 30, E). These can be sliced off, with a 

 surrounding margin of healthy tissue, in sections 3^8 mcn thick and then 

 dried in the press. Large fruiting bodies, such as the bracket fungi (fig. 

 30, A), associated with wood decay and tree rots, are collected whole 

 and merely dried. Root rots are often difficult to diagnose, especially in 

 small succulent plants. To make specimens of these, it may be best to 

 collect the entire plant, or, if too large, then at least the entire root. 

 Large roots may have to be sectioned. 



After drying, the specimens may be left in the newspaper sheets or 

 else transferred to large envelopes. Bulky material can be kept in paper 

 or cloth bags. 



Figure 32. — Leaf spot, highly magnified under hand lens, to show fruiting structures 

 of the fungus as small mounds. 



Plants often display symptoms or ailments which cannot readily be 

 traced to a specific cause. Yellowing of the leaves might be due to a 

 lack (or even excess) of certain chemical substances in the soil. A sudden 

 wilting or drooping of the leaves might be assigned to lack of water, or 

 to injury by some insect, such as a cutworm or stem borer. In fact, 

 symptoms of insect injury are sometimes similar to those caused by 

 fungi. The work of a leaf miner is often mistaken for a fungus leaf spot, 

 but the characteristic tunnels and excavations of the miner, or the insect 

 itself, usually will be revealed by holding the leaf to the light. Discolora- 

 tions and crinkling of the leaves caused by certain mites and plant lice 

 may be similar to those produced by certain fungi. Also, insect attacks 



