HOW PLANTS ARE SCATTERED 



375 



out long, leafless runners which root at intervals and so 

 propagate the plant, carrying the younger individuals off 

 to a considerable distance from the parent plant. 



Living branches may drop freely from the tree and then 

 take root and grow, after having been blown or been car- 

 ried by a brook or river to a favorable spot, perhaps hun- 

 dreds of yards away. The so-called snap-willows lose 

 many live twigs under conditions suit- 

 able for starting new trees. 



A slightly different mode of dis- 

 persal from that of 

 the raspberry is one 

 in which buds sepa- 

 rate from the plant 

 and serve to propa- 

 gate it. In the blad- 

 derwort (Fig. 264), 

 at the close of the 

 growing season, the 

 terminal buds are released by the decay of the stem and 

 sink to the bottom of the water in which the plants live, 

 there to remain dormant until spring. Then each bud 

 starts into life and gives rise to a new individual. 



444. Dispersal of Seed-Plants by Bulblets. Almost 

 every farmer's boy knows what "onion-sets" are. These 

 are little bulbs, produced at the top of a naked flower- 

 stalk or scape by some kinds of onions which do not 

 usually flower or bear seed. Tiger-lilies produce some- 

 what similar bulblets in the axils of the leaves, and there 

 is a large number of species, scattered among numerous 

 families of plants, all characterized by the habit of producing 



FIG. 264. A Free Branch and Two Buds of 

 Bladderwort. 



