DISPERSAL OF FRUITS AND SEEDS 223 



of the Poppy (Fig. 159, 4) is permanently covered, the small 

 seeds escaping through pores just below the lid. In Cam- 

 panulas with pendulous capsules the pores are at the base 

 of the capsule (Fig. 159, 5). In either case a strong wind 

 or jerk is necessary to shake out the seeds. 



B. Dispersal by water. The dry fruits and seeds of 

 plants growing along the sides of rivers and lakes may be 

 blown into the water and float a short distance before 

 sinking, or washed ashore farther down stream, where 

 they may germinate ; generally, however, they sink 

 rapidly. If carried seaward, most of them soon lose their 

 power of germination after entering salt water. Trunks 





Fig. 159. Censer Fruits. 1, follicles of Marsh Marigold ; 

 2, capsule of Red Campion ; 3, capsule of Snapdragon dehiscing 

 by pores ; 4, capsule of Poppy ; 5, capsule of Campanula. 



and branches of trees carried down stream often bear 

 seeds and fruits embedded in the mud adhering to them, 

 over long distances. Fragments of plants, especially of 

 water-plants capable of rooting, are often carried consider- 

 able distances, and provide an effective means of dispersal. 

 The Canadian Water-weed (Elodea), so common in our 

 ponds and canals, has spread extensively in Europe by 

 this means. 



The seeds of the White Water-Lily are surrounded by 

 a spongy aril, and between it and the seed-coat is air, which 

 enables the seeds to float until the air escapes, when they 

 sink to the bottom. In the Frog-bit and some Pond-weeds, 

 buds are formed in the autumn which become detached 



