22 ME. BEEKELEY OX THE POTATO MUEEAIX. 



place, where the disease appeared so early, and where indeed it 

 has been so severe, it does not appear to depend on free moisture 

 to the extent wiiich is your opinion of tlie matter. In the dis- 

 tricts of the porous greensand formation, which have generally 

 yielded our best crops, they have this year suffered the most ; 

 while in the cold, wet districts of tlie London clay, and 

 beds of plastic clay, and upper fresh-water formations, the crops 

 have been mucii less attacked. In one instance, in a clay soil, 

 and where the air had not been admitted by hoeing up, the po- 

 tatoes were almost unattacked. From all I can collect in this 

 district, exclusion of air appears to have been the greatest pre- 

 servative, either by depth of planting or even by agency of free 

 moisture on the surface. Though there has been so little dura- 

 tion, at any time during the summer, of weather free from rain, 

 yet the actual quantity of water which has fallen has been much 

 less than usual. Our springs have been very low, and during 

 the harvest period, when fortunately there was a short continu- 

 ance of dry weather, the effects of drought were most speedily 

 visible." 



It may be doubted, too, whether the water of vegetation has 

 always existed in the tubers in a greater proportion than usual. 

 The quantity of water in potatoes is stated by Boussingault as rang- 

 ing from 75"9 to 79*4 per cent. ; according to Payen it is some- 

 what lower. My own observations do not show any excess of 

 moisture in potatoes taken from tlie ground in the month of Oc- 

 tober, the crop being in an extremely diseased state. They 

 exhibited 74 per cent., the central substance of the tubers giving 

 73*5. Potatoes, from a cellar at the same time, in good con- 

 dition, gave 77*1. Mr. G. Phillips found on the 2nd of Oc- 

 tober 75-7 in a sound potato taken from the ground. In 

 another variety he found 78'0, and in a diseased white potato 

 79.* The potatoes, after they become diseased, probably when 

 placed in a moist situation, imliibe a certain quantity of moisture. 



Did the disease really arise from the water of vegetation exist- 

 ing in too great abundance, and lience inducing putrefaction of 

 the cellular substance, it woidd be difficult to say why it has not 

 existed to a considerable extent before. This spotted form of 

 decay is certainly not familiar to the cultivator, however long it 

 may have existed, though other forms are. 



I think then it is at least plain that no supposed peculiarities 

 of season are sufficient without some more specific cause to ac- 

 count for the general prevalence of this disease. 



* Monsieur Stas however asserts that all the potatoes of this year contain 

 less water and starch and more coagulable albumen than usual. He states the 

 water at 82-2. fComptes Rendu?, 184.5, p. €91.) 



