26 Graft- Infections Disease of Datura 



plant. Its two main branches were cut off a short distance above the 

 fork and on the left branch was grafted a purple Q. cion, recognized by 

 its eroded leaves, and on the right branch was grafted a purple normal 

 cion. The infection passed down the one branch and up the other into 

 the normal cion, causing the production of a capsule with a reduced 

 number of spines and a later capsule entirely smooth. The buds in 

 the stock below the fork also grew out with Q. characters, the one on 

 the left shows a single capsule with reduced spines and one entirely 

 smooth while the one on the right shows a single capsule likewise 

 entirely smooth. The infection is usually manifest as soon as new 

 leaves are formed and gradually spreads leaving the older parts, pro- 

 duced before the infection, free from abnormality and causing the new 

 growth to be more and more distinctly Q. in appearance. 



A number of other Solanaceous species, including several different 

 genera, were tested by grafting with Quercina Jimson Weeds. None 

 was found to be so susceptible to the disease as the Jimson Weed, 

 however. 



Datura meteloides could be infected by grafting, but the disease was 

 slow in showing. The disease could be brought back to the Jimson Weed 

 by grafting on it a cion of infected Z). meteloides. In PI. V, fig. 9 a cion 

 of this species is shown grafted on the normal Jimson Weed at the left 

 (marked Nor.) and a cion from the same plant was grafted on the 

 Q. plant on the right (marked Q.). The infection of the J), meteloides 

 shows as a mottling of the leaves with lighter patches and a puckering 

 of the leaf surface. This was the condition three or four months after 

 the graft. A few months later the leaves of the cion were free from 

 abnormal colour and puckering of their surfaces, but had their margins 

 deeply eroded. On such plants the flowers are devoid of pollen. Three 

 of such infected flowers were pollinated from a normal plant of B. mete- 

 loides and selfed seed from the pollen parent were taken as a control. 

 In comparison with the 10 individuals in the control, the 291 seedlings 

 from the Q. capsules of D. meteloides were obviously stunted and their 

 leaves of a paler colour. By the time of flowering, however, all of the 

 291 plants had recovered and showed no trace of infection except one, 

 which had lacerated leaves, flowers without pollen, and somewhat eroded 

 corollas. This plant. No. 18182 (1) is shown at the left in PI. VI, fig. 10 

 beside a normal plant from the same pedigree. The Q. disease is therefore 

 not so readily transmitted through the seed in Datura meteloides as in 

 D. Stramonium, although the former species acquires the disease slowly 

 through graft infection. 



