INTRODUCTION 15 



accuracy for all ordinary purposes — and measures up to 

 10 cm. 



In seeking expert help in identification care must be taken 

 to state very clearly in the case of supposed fungus galls 

 what information is desired. To my knowledge a cecidolo- 

 gist sent a cankerous outgrowth from a branch to a well- 

 known mycologist asking him to identify the fungus. He 

 examined the specimen, found a saprophyte on the bark, and 

 sent back its name. The collector, knowing nothing about 

 fungi, jumped to the erroneous conclusion that the sapro- 

 phyte was the cause of the gall growth. 



The shape, size, and position of the gall are secondary 

 characters in diagnosis. The occupants must be examined 

 carefully in all cases with a microscope or powerful pocket- 

 lens, for it sometimes happens that galls of similar appear- 

 ance caused by totally different creatures occur on the same 

 species of plant. Many egregious blunders have been made 

 (and unfortunately published) by cecidologists who have 

 omitted to observe this elementary precaution — e.g., galls 

 caused by eelworras have been ascribed to the presence of 

 dipterous larvae. 



The collector's field outfit should consist of a good-sized 

 vasculum (16 x 8 x 4J inches is as handy as any), a strong 

 pocket-knife, a stout prunmg-knife, a hand-saw with adjust- 

 able blade, a few small tin boxes, and a good pocket-lens. 



Fig. I.— Seed Pods of Lotus comiculatus, swollen and deformed 

 THROCGH THE PRESENCE OF THE Larvae OF Contarinia loH. (l/l.) 



