III.] SEEDS THRO WN B Y THE PARENT PLANT. 53 



dispersion of the seeds, or, speaking botanically, the 

 fruits, by the wind. When the grass is short, as, for 

 instance, in lawns, the intelligent plant keeps its stalk 

 also short. Some plants, as we shall see, even sow 

 their seeds in the ground, but these cases will be 

 referred to later on. 



In other cases the plant throws its own seeds to 

 some little distance. This is the case with the common 

 Cardamine hirsuta, a little plant, I do not like to call 

 it a weed, six or eight inches high, which comes up of 

 itself abundantly on any vacant spot in our kitchen- 

 gardens or shrubberies, and which much resembles 

 that represented in Fig. 3S. but without the subter- 

 ranean pods b. The seeds are contained in a pod 

 which consists of three parts, a central membrane, and 

 two lateral walls. When the pod is ripe the walls are 

 in a state of tension. The seeds are loosely attached 

 to the central piece by short stalks. Now, when the 

 proper moment has arrived, the outer walls are kept 

 in place by a delicate membrane, only just strong 

 enough to resist the tension. The least touch, for 

 instance, a puff of wind blowing the plant against a 

 neighbour, detaches the outer wall, which suddenly 

 rolls itself up, with such force as to fly from the plant, 

 thus jerking the seeds to a distance of several feet. 



In the common Violet, beside the coloured flowers, 

 there are others in which the corolla is either absent 

 or imperfectly developed. The stamens also are 

 small, but contain pollen, though less than in the 

 coloured flowers. In the autumn large numbers of 

 these curious flowers are produced. When very young 

 they look like an ordinary flower-bud (Figs. 37 and 38, 

 a), the central part of the flower being entirely covered 



