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violet spot more or less distinct at the base of each petal ; 

 on uplands the spots are less common, and the flower is 

 variable in this respect. A colony of V. cucullata was 

 found by the writer in a moist field, all the flowers of which 

 had white spots instead of blue ! These two colors, the 

 same as were produced artificially, were doubtless caused 

 by insects. 



Those artificially produced were not induced evidently 

 by any additional nutriment, or localization of new color 

 material, but rather by some chemical change in the sap 

 already present in the cells, caused by the stimulating effects 

 of the friction. 



A red variet}^ of poppy with large, round, white spots 

 instead of black, suggests a similar origin. 



Insects often indirectly change a color by changing the 

 character of the vegetable tissue. This is apparent in galls 

 and other excrescences produced by bites, punctures, or 

 stings. A small worm hatched from a minute egg in the 

 stem of Solidago rugosa, will cause by its irritation an en- 

 largement of the stem. This swollen part, if exposed to 

 the sun, generally becomes of a purple color, whereas the 

 rest of the stem and leaves is perfectly green; in like 

 manner red nodules are caused on the ribs of the green 

 leaves, and tendrils of the wild grape vine, and red excres- 

 cences on the oak and wild cherry, and white balls on oak 

 leaves, etc. The puncture of an insect may change the 

 green calyx of Oenothera biennis also to red. The change 

 of color in these examples follows some change in the char- 

 acter of the tissue and a change in form. Changes in the 

 forms of flowers and many peculiar outgrowths from the 

 petals are also caused by insect agency. 



If one sees the lip of an orchid, two, four or six times as 

 broad as the other segments and knows that that lip is 

 habitually used as an alighting place for the insects visiting- 

 it, he hardly needs a demonstration to prove that its enlarged 

 size was due to their presence. 



