202 Retrograde Varieties 



quite the same way, and since it is obviously 

 impossible to attribute them to an innate ten- 

 dency to reversion, they afford an absolutely 

 irrefutable proof of the assertion that pollen 

 is often brought by insects from one lot of 

 plants to another. In this way I obtained a 

 hybrid between the common Jacob's ladder and 

 the allied species Polemonium dissectum. With 

 a distance of 100 meters between them I had 

 two hybrid seeds among a hundred of pure 

 ones. At a similar distance pollen was carried 

 over from the wild radish, Raphanus Raphanis- 

 trum, to the allied Raphanus caudatus, and I 

 observed the following year some very nice hy- 

 brids among my seedlings. A hybrid-bean be- 

 tween Phaseolus nanus and P. multiflorus, and 

 some hybrids between the yellow daisy, 

 Chrysanthemum segetum and the allied Chrys- 

 anthemum coronarium or ox-eye daisy which 

 also arose spontaneously in my garden between 

 parents cultivated at recorded distances, might 

 further be noted. Further details of these ex- 

 periments need not be given. Suffice to say, 

 that occasional crosses between species do 

 occur, and not even rarely, that they are easily 

 recognized as such and cannot be confused with 

 cases of atavism, and that therefore they give 

 proof to the assumption that in the same way 

 crosses ordinarily occur also between varieties 



