252 



BOTANY OF THE LIVING PLANT 



occurred with one of Tomato (24), giving 96, which on reduction to form the 

 m-cells appears as 48. If this be so, then 5. darwinianum is a true graft- 

 hybrid. (For an explanation of the behaviour of chromosomes in Reduction 

 see Chapter XXXV.) 



The horticulturalist also induces the formation of adventitious buds, 

 and some plants respond freely. If a lamina of Begonia or of Gloxinia 

 be cut transversely across the main ribs, and be cultivated in heat on 

 damp soil, buds may be formed in relation to any cut vein. These buds 



root themselves in the soil as 

 new plants. It is stated that 

 each bud arises from a single 

 cell of the parent leaf. (Fig. 

 176.) Certain Fern-rhizomes, 

 and even the bases of their 

 leaves behave in a similar 

 way ; but it is in the Mosses 

 that there is the most re- 

 markable profusion of this ad- 

 ventitious development from 

 single cells of the injured part. 

 If moss plants be chopped up 

 into small pieces, any piece 

 in which an uninjured cell 

 remains may start a new 



vegetative 



growth 



a 



, and lead 

 new moss 



Fig. 176. 



Part of leaf of Begonia, bearing adventitious buds 

 after cultivation, in heat, on moist soil. 



ultimately to 



plant. 



There are certain weeds of 



farm land which depend upon 

 a somewhat similar vegetative multiplication for their survival, when 

 the land is worked by plough and harrow. The Couch Grass [Triticum 

 repens), and the Common Horsetail (Equisetum arvense) are cases in 

 point. Any node serves to provide new buds ; and as the long under- 

 ground rhizomes are broken up in preparing the soil, this does not 

 eliminate, but tends to spread the weed. 



It thus appears that vegetative extension and propagation of the 

 individual is a very wide-spread feature, both in Flowering Plants 

 and in those lower in the scale. It is effective in wild life, as well 

 as under the hand of the gardener. A very considerable proportion 

 of the perennial plants which we see have been so produced. This 

 applies especially to the Grasses and Sedges, whose perennial 



