22 . PROPAGATION OF ROOTS AND STEMS 



their twigs, or the storms break them off : many of these 

 twigs take root in the moist earth where willows grow, and 

 they are often carried down the streams and are washed 

 along the shoi-es of lakes. Observe the willows along a 

 brook, and determine whether any of them may liave come 

 down the stream. 



58. PROPAGATION BY MEANS OF LEAVES.— Even leaves 

 may take root and give rise to neiv plants. There are 

 examples in warm countries. The lake -cress of northern 

 streams also propagates in this way: the leaves with little 

 plants attached may often be seen floating down stream. 

 Gardeners propagate some kinds of begonias by means 

 of leaf cuttings; also gloxinias and bryophyllums. 



59. PROPAGATION BY MEANS OF BVDS.— Buds often 



become detached and j^ropagate the ])lant. Familiar 



examples are the bulblets of tiger lilies, borne 



amongst the foliage ; for all bulblets and 



bulbs are only special kinds of buds. Fig. 30. 



Some water plants make heavy winter buds, 



which become detached on the approach of 



cold weather and sink to the bottom. In 



* spring, they give rise to new plants. 



60. GRAFTS. — Sometimes a branch may 

 30. Buibiet of unite with another plant. A branch or a 

 trunk may lie against another plant of the 

 same kind, or of a very closely related kind, and grow fast 

 to it; and if its original trunk die away, the part will be 

 growing on an alien root. A branch which grotvs fast 

 to a branch of another plant, the wood of the two knit- 

 ting together, is called a graft. Fig. 31. It is necessary 

 to distinguish between a graft and a parasite: a parasite 

 prej's upon another plant, robbing it of its food, but a 

 graft becomes an integral part of the stock on which it 

 grows, and does its full work in elaborating food for 

 itself and for the stock. 



