58 EXPERIMENTS WITH KEEEKENCE TO THE POTATO DISEASE. 



Jersey Blue Potatoes planted in Jiills, the stems being lay- 

 ered and earthed up successively . — The results from hills 46 to 90 

 inclusive are given in Table IV. This differed from the pre- 

 ceding experiment in regard to layering the stems, and in their 

 receiving two earthings up instead of one. Soil for this could 

 not be dug from the alleys without interfering with the roots of 

 the potatoes ; it was therefore brouglit from another quarter. 

 In 24 out of 45 hills the tubers were all sound, but the average 

 quantity diseased was more, and the amount of sound produce less, 

 than where earthing up, without layering, was performed at once. 



A plot of ground was planted with potatoes in the Kitchen 

 Garden in the same manner as regards the depth of sets, distance 

 between the plants, and rows, as in the preceding experiments. 

 The ground was in good condition ; but had no manure when 

 the potatoes were planted. The varieties were tlie Early Manly, 

 Early Champion, and Cornish Kidney ; cut tubers were employed 

 for sets. The stems of all grew vigorously in the first instance ; 

 and in appearance the foliage was very healthy till the beginning 

 of June. But at an early stage, when the plants were only a 

 little above ground, it was found that the blanched part of the 

 stems below ground was faintly tinged with brown. The tinge 

 was at first quite superficial ; but it deepened to a more rusty 

 colour as the disease progressively effected the destruction of the 

 tissue. Fungi of course soon began to lay hold of the dead 

 matter. The spongioles were also affected ; still the plants showed 

 no signs of disease above ground till the beginninq: of June, as 

 above mentioned. After this the youngest foliage appeared of 

 too pale a green. In the middle of June blotches were observed 

 on some of the leaves. On the 18th of June the following ex- 

 periments were commenced : their results are given in Table V. 



Sulphuric acid, more or less diluted with water, was applied 

 to 6 contiguous rows of the Cornish Kidney, being distributed 

 over the tops by means of a watering-pot. The degrees of dilu- 

 tion were as follow : — 



1 . Sulphuric acid 1 part to 1 2 J parts of water, by measure. 



2. „ 1 „ 25 



3. „ 1 „ 50 



4. „ 1 „ 100 „ 



5. „ 1 „ 1.50 „ 



6. „ 1 „ 200 . „ 



The 6 row s to which the above were applied were each 22 feet 

 in length. 



Sidphuric acid 1 part to 12^ parts ofivater. — Table V. 1. 

 Tlie quantity to a row was 2 pints of sulphuric acid in 25 pints 

 of water. This, estimated per acre, amounts to 212 gallons of 

 sulphuric acid, and 2650 gallons of water. It was of course 



