200 Retrograde Varieties 



Once sure of this preliminary condition, the 

 experiment simply consists in growing a variety 

 at a given distance from its species and allow- 

 ing the insects to transfer the pollen. After 

 harvesting the seed thus subjected to the pre- 

 sumed cause of the impurities, it must be 

 sown in quantities, large enough to bring to 

 light any slight anomaly, and to be examined 

 during the period of blooming. 



The wild seashore aster, Aster Tripolium, 

 will serve as an example. It has pale violet or 

 bluish rays, but has given rise to a white va- 

 riety, which on testing, I have found pure from 

 seed. Four specimens of this white variety 

 were cultivated at a distance of nearly 100 

 meters from a large lot of plants of the bluish 

 species. I left fertilization to the bees, har- 

 vested the seeds of the four whites separately 

 and had from them the following year more than 

 a thousand flowering plants. All of them were 

 of the purest white, with only one exception, 

 which was a plant with the bluish rays of the 

 species, wholly reverting to its general type. As 

 the variety does not give such reversions when 

 cultivated in isolation, this sport was obviously 

 due to some cross in the former year. In the 

 same way I tried the white Jacob's ladder, 

 Polemonium coeruleum album in the neighbor- 

 hood of the blue-flowered species, the distance 



