41 6 Minnesota Plant Life. 



Especially in the flowering dogwoods and dwarf cornels, with 

 their conspicuous bracts below the heads of flowers, did there 

 arise an adaptational response to the tastes and habits of insects, 

 equivalent to that secured in sunflowers by the specialization of 

 the ray flowers. In the bunching of the edible fruits of dog- 

 woods and in their high coloration, the fruit-cluster, as such, 

 became a definite factor in the mechanism of seed distribution ; 

 for the aggregation of the fruits made them more attractive to 

 birds and animals, therefore more likely to be disseminated than 

 if they had been scattered loosely over the general surface of 

 the plant. In composites, winged distribution has, for the most 

 part, been adopted, and in this family highly colored, pulpy and 

 edible fruits do not exist. The aggregation of the flowers, how- 

 ever, is perfected and the co-operation of the calyx, from which 

 the pappus is formed, makes the distribution of the fruits quite 

 as certain as among the dogwoods. 



A sunflower head may, upon the whole, be regarded as the 

 most perfect structural response to the static conditions of the 

 plant world, just as the human head, with its wonderfully per- 

 fected brain and sense organs, may be regarded as the highest 

 structural response to the dynamic conditions of the animal 

 world and of animal life. 



