10 I.UTHER BURBANK 



If you dotely exmmine the calln will 



obterrc that what you would caniaiiy 

 of as a single bluiau is in reality a cast or 

 shield — in point of fact a modified leaf- 

 twisted into a sort of oonmcopia and nd justed 

 about a central stalk or "spad hieh 



many minute and inconspieiious bk>saouis are 

 dustered. 



The object of this arrangement is doubtleat 

 in part to give protection to the flowers, but 

 largely to supply a conspicuous signal to attract 

 nil^t-roiring insects* in particular various spedcs 

 of mall gnats and flics. 



In point of fact the white canopy of the calla 

 affords a ver>' convenient place of refuge for 

 numerous small insects. 



Tests have shown that the air inside the calla 

 "blossom,*' particularly toward its base, where 

 the insects congregate, is perceptibly wsriner 

 than the outside air. 



It has been proved by recer 

 that the chemical processes associatcu wim piunt 

 growth generate heat. Germinating seeds, for 

 example, give out a measurable quantity of heat. 

 So it is not strange, perhaps, that the partially 

 confined air at the base of the tubular calla 

 flower cnse is at all times a little warmer than 

 the surrounding atmosphere. 



