56 REASON OF DIFFERENCES. [chap. 



(Fig. 39) resembling an inverted tripod. Each valve 

 contains a row of three, four, or five brown, smooth, 

 pear-shaped seeds, slightly flattened at the upper, wider 

 end. Now the two walls of each valve, as they become 

 drier, contract, and thus approach one another, thus 

 tending to squeeze out the seeds. These resist some 

 time, but at length the attachment of the seed to its 

 base gives way, and it is ejected several feet, this 

 being no doubt much facilitated by its form and 

 smoothness. I have known even a gathered specimen 



Fig. -y^.— Viola canina. Seed vessels with seed. 



throw a seed nearly 10 feet. Fig. 40 represents a 

 capsulegafter the seeds have been ejected. 



Now we naturally ask ourselves what is the reason 

 for this difference between the species of Violets ; 

 why do V. odorata and V. hirta conceal their capsules 

 among the moss and leaves on the ground, while V. 

 canina and others raise theirs boldly above their heads, 

 and throw the seeds to seek their fortune in the world ? 

 If this arrangement be best for Viola canina, why has 

 not Viola odorata also adopted it ? The reason is, I 

 believe, to be found in the different mode of growth 



