LUTHER BURBANK 



But to complete the experiment, it is desirable 

 to mark the flower, and to repeat the manoeuvre 

 on several successive days. This is necessary be- 

 cause not all the flowers in the head mature at 

 the same time. The outer come to perfection first, 

 and the process of maturing advances towards the 

 center of the flower. So the first poUenizing must 

 be done just at the right time, and successive pol- 

 lenizings day by day until the entire flower has 

 come to maturity, if all the pistils are fertilized. 



It is obvious, then, that the crossing of dahlias, 

 while it presents no real difficulties, aiid is toler- 

 ably sure in its results, is a somewhat tedious and 

 laborious process where the field of operations is 

 wide. But, as already pointed out, it is not neces- 

 sary for the experimenter who is seeking merely 

 to modify existing varieties to resort to hand- 

 pollenizing. 



The varieties that will appear among any ordi- 

 nary lot of seedlings will afford him ample oppor- 

 tunity for selection. 



On the other hand, the experimenter who 

 wishes to develop new types of striking individ- 

 uality will of course crossbreed the old ones, using 

 species or varieties as widely separated as pos- 

 sible. My o-wn experiments, as already pointed 

 out, have involved the use of wild species from 

 Mexico, and the influence of these wild crosses has 



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