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THE POPULAR SCIENCE MONTHLY. 



When the seeds are fully ripe, the capsule opens by three valves and 

 allows them to escape. 



In the dog-violet ( Viola canina, Fig. 3) the case is very different. 

 The capsules are less fleshy, and, though pendent when young, at 



Fig. 3. Viola canina. a, bud ; ft, bud more advanced ; c, capsule open, some of the seeds are 



already thrown. 



maturity they erect themselves (Fig. 3, c), stand up boldly above the 

 rest of the plant, and open by the three equal valves (Fig. 4) resem- 

 bling an inverted tripod. Each valve contains a row of three, four, or 

 five brown, smooth, pear-shaped seeds, slightly flattened at the upper, 



Fig. 4. 



Fig. 5. Viola canina; seed-vessel 

 after ejecting the seeds. 



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 



