LUTHER BURBANK 



observe that what you would casually speak of 

 as a single blossom is in reality a case or shield — 

 in point of fact a modified leaf — twisted into a 

 sort of cornucopia and adjusted about a central 

 stalk or "spadix" on which many minute and 

 inconspicuous blossoms are clustered. 



The object of this arrangement is doubtless in 

 part to give protection to the flowers, but largely 

 to supply a conspicuous signal to attract night- 

 roving insects, in particular various species of 

 small gnats and flies. 



In point of fact the white canopy of the calla 

 aff'ords a very 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 warmer than 

 the outside air. 



It has been proved by recent experiments 

 that the chemical processes associated with plant 

 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-case is at all times a little warmer than 

 the surrounding atmosphere. 



In any event the insects find this a snug corner, 

 the attractiveness of which is further enhanced by 



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