[Chap. XXXV VEGETATIVE MULTIPLICATION 419 



apple, pear, and quince. Intergrafting among genera is possible in plants 

 of the potato family, and in plants of the sunflower family, but inter- 

 grafting between families of plants is rare. The idea that horticulturists 

 can make a kind of "table d'hote" plant through multiple grafting of 

 tomatoes, cucumbers, potatoes, apples, beans, and other plants is not 

 based upon reliable data. 



Effects of scion and stock upon each other. Removing a cutting from a 

 plant and placing it in soil, or grafting it on to the stem or root of another 

 plant, does not change its heredity. Both the stock and the scion retain 

 their inherent qualities, but do not acquire new ones from each other. 

 Each of them, however, is a part of the environment of the other. They 

 become physically united as parts of the same individual, and as such 

 they are subject to the interrelation of the parts of an individual as 

 described in Chapter XXI. 



The scion is dependent upon certain processes in the roots of the stock, 

 and the stock is dependent upon certain processes in the leaves of the 

 scion. Sugar, hormones, and other soluble substances pass from one 

 to the other. Nicotine, for example, may pass from a tobacco scion into 

 the roots and tubers of a potato stock. It is reported that when potato and 

 tomato are intergrafted with jimson weed, an alkaloid, atropin, from the 

 jimson weed accumulates in the tuber of the one and the fruit of the 

 other. As a result of these interrelations, the growth of roots and tops, the 

 size and flavor of fruits, and the time of flowering may be altered. 



Graft chimeras. A stem primordium mav develop bv the division and 

 enlargement of cells at the area of contact of scion and stock. If some of 

 the cells of this primordium develop from one or more cells in the base 

 of the scion and some of them develop from adjoining cells in the stock, 

 the young stem tip will be composed of the two kinds of cells, which may 

 be referred to briefly as "scion cells" and "stock cells." Since this stem 

 tip is the forerunner of a leafy branch, these cells are the remote fore- 

 runners of all the tissues that develop in it (Fig. 32). Consequenth 

 whole tissues in the leaves and stems of this branch may be composed 

 entirely of the one or the other kind of cell. The epidermis, for example, 

 may be composed entirely of scion cells, and the other tissues entirely 

 of stock cells. Such compound structures are called chimeras; and since 

 they develop from the junction of a graft, they may be called graft 

 chimeras to distinguish them from mutant chimeras, which originate 

 within cells by processes described in Chapter XXXIX. 



In time flower primordia may develop on stem tips of this branch. 

 These flower primordia may develop entirely from scion cells, entirely 



