A. F. Blakeslee 21 



near the station, including pedigrees planted close and far apart. 

 There were at this time also 88 Q. seedlings planted in the station 

 plot. 



In that year representatives of certain of the pedigrees were grown 

 in a " spread " plot with the individuals spaced five feet apart. Plants 

 in these spread plots had an extremely high percentage of incidence 

 (26*4 °/^ out of 167 individuals), while plants from the same pedigrees 

 elsewhere in the field, but spaced the customary one foot apart, showed 

 only the usual proportion of Q. plants (I'G °/„ out of 643 individuals). 

 The larger number of Q.'s in the spread plots may have been due to 

 the relatively enormous size of these plants which were not reduced in 

 growth by their neighbours. Each plant therefore gave a greater area 

 exposed to infection, and infection once taking place was carried to all 

 the numerous branches of the plant. Infection on the branch of a 

 plant in the more crowded plots, on the other hand, was apparently 

 unable to infect more than the few branches organically connected 

 with it since plants adjacent to Q.'s and with their branches touching 

 seem no more likely to acquire the infection than if adjacent only to 

 normals. What the carrier of the virus may be is at present unknown 

 but evidence beside that just given leads to the belief that the Q. 

 disease is not communicated by mere contact. 



Apart from its appearance in our cultures, we have found Q. plants 

 upon two occasions. Once in Staten Island where several such plants 

 were discovered, and once at Woodbury, Long Island, where a single 

 Q. plant was found among a group of 182 normals. One out of five 

 seedlings from the latter plant was a Q., but none of the four seedlings 

 from the Staten Island material turned out Q. The writer has in- 

 spected relatively few Daturas growing wild. It is probable that a 

 more careful search would show the disease not uncommon in wild 

 plants. 



IV. Breeding Experiments. 



(a) Inheritance of Q. through Female Gametes. 



While it was still thought that Q. was a genetic mutant, a con- 

 siderable amount of breeding work was carried on combining it with 

 all the available types of Jimson Weeds. No varietal immunity has 

 been discovered within the species. From the four capsules produced 

 by the first Q. plant discovered in 1915, 120 seedlings were produced, 

 of which 53 were normal and 67 Q.'s. Breeding work with typical 

 plants of the latter class was can-ied on in the greenhouse in 1915-16. 



