252 



Journal of Agricultural Research VoI.xvu.No. 



mottling. In order to study the behavior of the plants from which the 

 scions were taken, these plants as well as the scions and stocks were 

 labeled. Their performance is indicated in Table II under the heading 

 of "Condition of parent vine." The grafts were made when the plants 

 were from 4 to lo inches in height. In the majority of cases the cleft- 

 graft method was used. After the insertion of the scion the contact 

 between scion and stalk was effected by wrapping tightly with adhesive 

 tape. The performance of these grafts is recorded in Table II. 



Table II. — Grafts of potato vines, Presque Isle, Me., igi8 



These results indicate plainly that distinct mottling of the healthy 

 scions grafted upon diseased stocks had developed by the end of four or 

 five weeks, whereas no mottling developed on either the parent plants 

 or the healthy scions grafted upon healthy stocks. (See PI, 27, A, B.) 

 A few new shoots from stocks supporting affected scions showed mottling, 

 but since only a small number of these grafts were made the results are 

 inconclusive. 



In the winter of 191 8-1 9, 61 Green Mountain grafts were made at 

 Orono, Me., by means of the cleft-graft method already described. Of 

 the 50 which survived, 14 consisted of healthy scions on healthy stocks 

 and remained entirely healthy for from 43 to 82 days, 9 making new growth 

 from the stock and i from the scion; 15 consisted of healthy scions on 

 mosaic stocks; and 7 of these, or 41 per cent, developed mosaic on the 

 scion in from 21 to 44 days, although the plants from which the scions 

 came remained healthy. In the 7 mosaic scions there was usually a con- 

 tinuation of leaf expansion, and the mosaic symptoms developed in the 

 youngest leaves. The scions which remained healthy usually showed no 

 good growth. Of 21 grafts consisting of a mosaic scion and a healthy 

 stock, the one whose stock produced the most new growth showed 



