HOW PLANTS ARE SCATTERED 



377 



the structure of the seeds themselves, sometimes to that 

 of the fruit in which they are enclosed ; the essential 

 point is to have transportation to a long distance made 

 as certain as possible, to avoid overcrowding. 



446. Explosive Fruits. — Some dry fruits burst open 

 when ripe in such a way as to throw their seeds violently 

 about. Interesting 

 studies may be made, 

 in the proper season, 

 of the fruits of the 

 common blue violet, 

 the pansy, the wild 

 balsam, the garden 

 balsam, the crane's- 

 bill, the herb Robert, 

 the witch-hazel, the 

 Jersey tea, and some 

 other common plants. 

 The capsule of the 

 tropical American 

 sand-box tree bursts open when thoroughly dry with a noise 

 lite that of a pistol shot. 



447. Winged or Tufted Fruits and Seeds. — The fruits 

 of the ash, box-elder, ehn, maple (Fig. 169), and many 

 other trees, are provided with an expanded membranous 

 wing. Some seeds, as those of the catalpa and the trunlpei^ 

 creeper, are similarly appendaged. The fruits of the 

 dandelion, the thistle (Fig. 267), the fleabane, and many 

 other plants of the group to which these belong, and the 

 seeds of the willow, the milkweed (Fig. 267), the willow- 

 herb, and other plants, bear a tuft of hairs. 



Fig. 266. — Fruits of Linden, witli a Bract joined 

 to the Pedvinole and forming a Wing. 



