Some 



Experiments of I^uther Bur bank 



DIAGRAM 



Showing the Zone of Life and Parallelism of Resuits in 

 Crossing and Grafting. (L. B.) 



Utter refusal to unite under any circumstances, either by /// 

 VV\ crossing or grafting. (Outside of zone of possible union. ) // 



Pollen acts as a poison. 



Union partial, mosaic or tem- 

 porary; seed rarely produced; 

 seedlings generally inherit ten- 

 dencies and qualities of one 

 parent only; second or later 

 generations revert fully. 



Union free; seedlings show 

 unbalanced condition, varying 

 widely; often unusually vigor- 

 ous; best condition for scien- 

 tific or natural selection. Good 

 qualities can be made perma- 

 nent to the race. 



Unite freely; seed of super- 

 ior germinating quality pro- 

 duced abundantly. Seedlings 

 normal with ordinary amount 

 of variability. 



Grafts blight and die as if 

 poisoned. 



Grafts often form a tempor- 

 ary union but are not in a nor- 

 mal condition. Avoided by 

 nurserymen and planters with 

 great care, as results are often 

 disastrous to the grower. 



Grafts unite readily but sepa- 

 rate under unusual stress — 

 drought, overbearing, lack of 

 nourishment, etc. Avoided by 

 nurserymen and planters. 



Mutative. 

 State. ' I 



Large Grafts unite readily, thriving 



Variation, well ; sometimes better than 

 when grafted on their own 



\\V// 



Mendelian 

 State. 



Ordinary plant life as oftenest Usual Grafts unite and thrive 

 met with. Fluctuations, we oftenest see them. 



Self-f ertile ; seed produced, 

 but as there are very limited 

 opportunities for profitable var- 

 iations, this state ultimately 

 ends in 



V 



Grafts grow on their own 

 roots. 



Extinction. 



All these varying states shade off from one to the other, 

 with few hard and fast lines of separation. 



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