1374 DISEASES NOT DUE TO PAKASITlCS OR OF I'NKXOWX OKIGIX 



As a general rule, the disease is reproduced on the first buds of the slip, 

 with the same intensity and the same appearance as it had exhibited in 

 the previous year on the corresponding leaves and the internodes of the 

 branch of the parent vine. 



Furthermore, the experiments described in this work have brought 

 out a number of shades and gradations of this phenomenon of preserva- 

 tion of bramble-leaf in the layer-slips so much so as to point to the possi- 

 bility of an effective, slow and gradual cure of plants taken from diseased 

 vines. 



The slips of the Berlandieri and their hybrids, the European-Ameri- 

 can hybrids and Riparia, above all, recovered more rapidly during the sum- 

 mer than the slips of Rupestris, and among the latter varieties the most 

 liable to the disease are the most difHcult to cure. For instance, the pro- 

 portion of plants which recovered in summer, all conditions of soil and rear- 

 ing being equal, is less in the case of the varieties of Rupestris du Lot 

 than of Rupestris metallica. 



Furthermore, the more readily the diseased slips take root in a given 

 soil, the more easily they recover. The recovery which occurs in summer is 

 proportional to the root growth, in respect both to the number and thick- 

 ness of the roots put forth by the slip. It follows rather than precedes the 

 production of root apparatus sufficing for the needs of the aerial portion. 

 The question involved therefore is that of an abundance of roots relatively 

 to the size of the slip. For instance, a plant with fine stalk recovers in summer 

 even if it has only few roots, while a slip as thick as those often taken at the 

 base of branches, needs the growth of numerous roots before equifibrium 

 is established between the demands of the foliage and the potentiafities 

 of the absorption apparatus. 



Whatever the factor influencing the production of roots, it also in- 

 fluences the recovery of the diseased branches in .summer. Thus the treat- 

 ment of the slips with different baths at the time of planting very much 

 facilitated their recovery, not owing to any disinfecting action, but because 

 some of the substances applied stimulated exchanges favourable to a great- 

 er root production. In 1907 the best results were obtained with ferrous 

 sulphate, phenol and hot water ; in 1908, with phenol, ferrous sulphate and 

 hot water ; in 1909, with formalin, phenol, acids and hot water ; in 1910, 

 with ferrous sulphate, sulphuric acid and lysol. 



The difference observed between the behaviour of diseased slips planted 

 on propagation beds already partly exhausted by use and those planted on 

 beds which had been fallowed, was still more interesting. In the latter case 

 the diseased slips at once formed a strong root system, while in partly used 

 up soil the diseased slips struck root verj^ poorly, and in summer there 

 was little or no recovery. 



The writer has made trials of different crops with a view to finding out 

 which is most adapted to rest the fatigued soil for the purpose of vine-grow- 

 ing ; leguminosae contributed largely to better rooting of the slips, and on 

 the beds where bean ensilage had been carried out the proportion of reco- 

 veries in summer was usuallv found to be higher. 



