194 ON SEEDLINGS 



their nests, and I am inclined to suspect that they mistake 

 them for the pupae of other ants. 



Some Violets throw their seeds. In the Dog Violet 

 (V. canina) the capsules, though pendent when young, at 

 maturity raise themselves l above the rest of the plant, and 

 open by three equal valves resembling an inverted tripod. 2 

 Each valve contains a row of three, four, or five brown, 

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

 wider, end. The two walls of each valve, as they become 

 drier, contract, and 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 

 throw a seed nearly ten feet. 



On the other hand, in Viola hirta the capsules hang down, 

 and it has been said actually bury themselves in the ground. 

 ' 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 erect theirs and throw 

 the seeds to a distance ? If this arrangement be best for Viola 

 canina, why has not V. odorata also adopted it ? The reason is, 

 I believe, to be found in the different mode of growth of 

 these two species. V. canina is a plant with an elongated 

 stem, and it is easy therefore for the capsule to raise itself above 

 the grass and other low herbage among which Violets grow. 



' V. odorata and V. hirta, on the contrary, have in ordinary 

 parlance no stem, and the leaves are radical, i.e. rising from 

 the root. This is at least the case in appearance, for, botani- 

 cally speaking, they rise at the end of a short stem. Now 

 under these circumstances if the Sweet Violet attempted to 

 shoot its seeds, the capsules not being sufficiently elevated, the 

 seeds would merely strike against some neighbouring leaf, and 

 immediately fall to the ground. Hence, I think, we see that 

 the arrangement of the capsule in each species is that most 

 suitable to the general habit of the plant.' 



Cotyledons. The only seedlings I have seen of this Order 



1 Lubbock's Flowers, Fruits, and Leaves, p. 55 (fig. 38 c). * Ibid. p. 56. 



