20 PROPAGATION BY MEANS OF ROOTS AND STEMS 



throw up shoots or new plants. Severed roots often grow. 

 Blackberries, raspberries, and many plums and cherries, 

 throw up shoots or "suckers" from the roots; and this 

 propensity is usually increased when the roots are broken, 

 as by a plow. Broken roots of apples often sprout. Plants 

 may propagate by means of root-cuttings. 



54. Occasional Buds. The buds that appear on roots 

 are unusual or abnormal, they occur only occasionally and 

 in no definite order. Buds appearing in unusual places on 

 any part of the plant are called adventitious buds. Such are 

 the buds that arise when a large limb is cut off, and from 

 which suckers or watersprouts arise, as on the apple tree. 



55. Layers. Roots sometimes 

 arise from aerial stems that are 

 partially buried. If a branch 

 touches the ground and takes 

 root, it is called a layer. Gar- 

 deners often bend a limb to the 

 ground and cover it for a short 

 distance, and when roots have 

 formed on the covered part, the 

 branch is severed from its parent 

 and an independent plant is 

 secured. See Fig. 30. 

 56. There are several kinds of layers: a creeper, when a 

 trailing shoot takes root throughout its entire length; a 

 runner, when the shoot trails on the ground and takes root 

 at the joints, as the strawberry; a stolon, when a more or less 

 strong shoot bends over and takes root, as the black rasp- 

 berry or the dewberry (Fig. 30); an offset, when a few very 

 strong plants form close about the base of the parent, par- 

 ticularly in succulent or bulbous plants, as house-leek 

 (old-hen-and-chickens) and some lilies. The rooting branches 

 of the banyan and mangrove (Figs. 15, 16) may be likened 

 to layers. 



30. A layer of dewberry. The new 

 plant has arisen at the left. 



