CHAPTER XXXV 

 VEGETATIVE MULTIPLICATION OF FLOWERING PLANTS 



Most flowering plants may increase in number by either of two methods : 

 ( 1 ) the formation of special reproductive cells and seeds — sexual repro- 

 duction, or (2) the development of a separate individual from one or 

 more vegetative cells of a plant — vegetative multiplication or vegetative 

 propagation. The vegetative organ, or any fragment of it, from which the 

 separate individual develops may be referred to as a vegetative propa- 

 gule, in contrast to a seed. 



If two or more separate individuals develop from single vegetative 

 cells or from branches of the same plant, they are merely isolated parts 

 of it. They are "chips off the same block," not a new generation of plants. 

 These facts are most readily appreciated when vegetative multiplication 

 by cuttings is considered. 



We mav, for example, cut a thousand twigs from a willow tree in early 

 spring and place the basal end of each twig in moist aerated soil. These 

 severed twigs are cuttings. Within a few weeks roots develop from the 

 lower nodes of each cutting, and branches grow from the buds above 

 the soil. Thus within a short period of time we can secure a thousand 

 young willow trees, which may in turn become large trees. 



These thousand separate trees, however, are as much alike inherently 

 as are the unsevered branches of a single tree; and in all matters per- 

 taining to pollination, sex, and hereditv they should be considered as 

 branches of the tree from which the cuttings were taken. Branches of 

 each of these thousand trees mav in turn be used as cuttings, and so on 

 ad infinitum. In this manner a single generation of a willow tree may be 

 perpetuated and multiplied indefinitely. It is often convenient to have a 

 name to refer to all the individuals which through repeated vegetative 

 multiplication have a common origin. Such individuals are collectively 

 called a clone. Their common origin is the embryo of the first individual 

 of the clone (Fig. 175). 



All the individuals of the Concord grape constitute one clone, for this 

 variety of grape has been perpetuated by vegetative multiplication since 



400 



