GRAFTAGE 109 



purple flowers. Yellow flowers are characteristic of Laburnum 

 vulgare, and purple flowers are borne by C. purpureus, but the pink 

 is truly intermediate. The wood and foliage accompanying each 

 type of flower followed the characteristics of the parent from which 

 it came. This graft was propagated and is known as Cytisus Adami. 

 Biologists are not willing to call this a graft hybrid, however, for 

 they point out that the tissues are not hybrid. The outer tissues 

 of C. Adami are distinctly C. purpureus and the inner tissues Labur- 

 num vulgare. 



Many other examples of so-called graft hybrids have been 

 found. In 1914, D. Bois, in Revue Horticole, reported the case of 

 a Pear grafted on a Quince, which sent out below the graft two 

 opposite branches; one was of the Quince growth, the other dif- 

 fered widely from both Pear and Quince. It was called Pyrocy- 

 donia Winckleri.* It is reported that this variation is propagated 

 true to type. 



The settlement of the question whether such growths are truly 

 hybrid is important, for if they are, sexual and asexual reproduc- 

 tion are identical. Hybrids are supposed to occur only as the result 

 of the union of the sex cells, not the structural cells, of a plant. 



CHARACTERISTICS OF AN IDEAL STOCK 



A good stock for budding or grafting should be: 



1. Hardy, if possible, so that the plants may live through the 

 Winter. 



2. Easily, simply and rapidly multiplied. 



3. Cheap to obtain; many stocks are grown from seeds gathered 

 from the wild. 



4. Free from susceptibility to pests and diseases. Certain 

 plants being very susceptible to pests are grafted for this reason. 

 The European Grape being readily attacked by the Phylloxera, a 

 root louse, is grafted upon the American Grape stock which is not 

 attacked. Diseases are readily communicated from stock to cion 

 or vice versa. 



5. Easy to work; looseness of bark for budding is a prominent 

 asset. 



6. Capable of making good strong unions and uniting quickly; 

 the cion should not outgrow the stock. 



7. Able to produce a good, well-balanced root system. In the 

 case of many commercial plants, a small but very fibrous root sys- 



* Bois, D. Pyrocydonia Winckleri. Revue Horticole, Jan. 16, 1914, pp. 27-29. 



