22 PLANT-BREEDING 



from the visits of insects by paper bags and sowing, each 

 year, the seeds of some few normal individuals of the race 

 This pedigree embraces, now, about a dozen generations, 

 the first few of which were biennial, but the later annual. 

 From tliis stock of normal plants it has regularly repeated its 

 first mutation, producing some latas in almost every genera- 

 tion. The number of these mutants was, on the average, 

 about i^ per cent, the mutants themselves being always alike. 



Moreover, my pedigree culture has produced quite a 

 number of other mutants. The most frequent among them 

 is a dwarfish variety, the first flowers of which open when the 

 stem is only some few inches high. It is called Oenothera 

 nanella and occurs as frequently as the (Enothera lata. It 

 is completely fertile and produces an abundance of seeds, all 

 of wliich give the same dwarf type, without (>ver reverting to 

 the high stature of the parent species. I have cultivated 

 these dwarfs during five, and more, generations and have 

 found them true to their type. 



The first generations of my pedigree culture had to meet 

 with all the difficulties of a new experiment with unknown 

 and partly unsuspected results. Accordingly, they yielded 

 only a small number of mutants. As soon as the method had 

 been elaborated, this number rapidly increased. In the 

 spring of 1895 I sowed seed enough to have about 14,000 

 young seedling plants, which I cultivated until they clearly 

 showed whether they would mutate or not. The mutating 

 individuals were than isolated and grown under very favor- 

 able conditions, but of the normal plants the larger part were 

 destroyed. All in all, I isolated 60 dwarfs and 73 lata and 

 five wholly different new types. Two of them were rare, one 

 having been found only in one (O. gigas)and the other in two 

 individuals (O. leptocarpa). Two others were less rare, the 

 rubrinervis appearing in eight, and the albida in fifteen speci- 

 mens. The fifth was the most frequent of them all, spring 



