VEGETATIVE REPRODUCTION 



161 



extreme cold, and the food destined for them goes into 

 the little plants instead. 



7. Multiplication by Detached Shoots — e.g., some aqua- 

 tics' (see p. 53). 



It is clear from this that the vegetative mode of repro- 

 duction in aU its various forms is really one of bvd- 

 detachment. Bulbs, corms, and bulbils are obviously 

 only buds rich in food-reserves. 

 Cuttings, fragments of rhizomes, 

 ruimers, duckers, and tubers are 

 modified bud-bearing shoots. In 

 viviparous roots and leaves buds 

 arise on organs which normally do 

 not bear them. It seems, indeed, 

 as if any part of a plant, which con- 

 tains soft tissue capable of growth, 

 may produce buds if a sufficient 

 stimulus is present. One condi- 

 tion is always necessary — abimd- 

 ance of food at the points where 

 the buds are destined to form. 

 The stimulus in most cases is pro- 

 vided by some check taking place 

 in the ordinary processes of growth, 

 and a transference of vegetative 

 activity to new centres — the 

 brood-buds. The bud is, there- 

 fore, the basis of vegetative multi- 

 plication in the higher plants, and 

 its success is due to — 



1. The reserve - food stored 

 up in the bud itself or in 

 organs closely connected with it. 



2. Its power of developing adventitious roots, with- 

 out which independent life would be impossible. 



3. Its xerophytic nature, enabling it to remain in a 

 resting or dormant condition during the periods un- 

 favourable to vegetative growth. 



4. In many cases to the protection secured to it by 

 living underground. 



Fig. 65. — Poa alpina, 



SHOWING EePLACEMENT 



OF Floweks by ViviPAa- 

 ous Plantlets. (After 

 Kebner.) 



11 



