58 



HORTICULTURE FOR SCHOOLS 



Roots do not usually develop from the callus, but callus 

 formation generally must precede root formation. 



83 . Leaf - cuttings. Some 

 plants possessing thick fleshy 

 leaves with an abundance of 

 stored food can be propagated 

 by leaf-cuttings. Leaves of 

 Bryophyllum placed on moist 

 sand in the cutting-bed will pro- 

 duce plants from the notches 

 in the leaves (Fig. 33). Most 

 leaves have to be wounded in 

 order to be able to send out 

 shoots in this manner. The Rex 

 begonia leaf will produce plants 

 if its ribs are wounded and 

 it is pegged down in sand. It 

 is not necessary to use the whole 

 leaf, a piece planted edgewise being sufficient. In the same 

 way, tomato leaves, if the bud at the base is included, will 

 produce plants. Other kinds which may 

 be propagated in this manner are the 

 cabbage, rose, lemon, and lilac, but few 

 are so reproduced commercially. Leaf- 

 cuttings produce plants true to variety 

 except that they do not transmit the 

 irregular white or yellow spots or 

 blotches on leaves known botanically 

 as variegations. 



84. Tuber -cuttings. Tubers are 

 thickened underground stems having an 

 abundance of stored food, and pos- 

 sessing buds capable of producing plants. 

 The stems grow from the buds or eyes, 

 and from the stems roots develop. When a portion of the 



FIG. 32. Callusing of cuttings. In the 

 longitudinal section the callus orig- 

 inating at the cambium has forced 

 out the several layers of bark. 



FIG. 33. A leaf-cutting. 



