Theory of Plant Breeding 



cent, of a certain iris and which belonged to the inner 

 row of three stamens which are usually absent. 



By breeding from these exceptional irises he, in 1894, 

 found that 89 per cent, had extra stamens, and in 1895 

 that 56 flowers out of 486 had six stamens, and also 

 had all three petals changed so as to resemble the sepals.-^' 

 So that pure races may occasionally revert even to 

 extremely distant ancestors. 



Another different question, which is also full of interest 

 to all practical horticulturists, is the influence of the 

 stock upon the scion, and vice versa. Mr. Daniel has 

 published many observations upon this question and 

 upon grafting generally. When, for instance, a perennial 

 sunflower was grafted upon an annual one the stock 

 became perennial, and other characters of the scion also 

 made their appearance on the stock. 



Such characters as variegation, early flowering, fertility, 

 resistance to cold and to parasitic fungi, have also been 

 produced in the graft when attached to a suitable stock.^^ 



It was by the use of American stock which were un- 

 affected by the Phylloxera that the French and other 

 vineyards were saved from destruction, but in this case 

 the grafts were not (at least so far as the author is 

 aware) influenced by the American stock. 



But these difficult questions must not be allowed to 

 occupy too much space, and we cannot do better than 

 close this chapter with an illuminating remark by the 

 late Professor Weldon, ^' There is probably no group of 

 plants or of animals which cannot be directly modified 

 by a suitable change in some group of environmental 

 conditions." ^^ 



1 Thomson. ^ Dg Vries. ^ Korschinsky. 



* Garjeanne. ^ Molliard. ^ Henslow. 



' Arnott. * Blaringhem. ^ Von Wettstein, Henslow. 



1" Bateson. i' Wilks. ^^ ^nd " Hurst. 



^* Saunders. ^^ Davenport. ^^ Chittenden. 



^' and 1* Heinricher, Jones. ^* Weldon. 



306 



