324 Memoirs u/' the Caledonian Horticultural Socieij/. 



had conie with tlie manure; but, in other iiibtaiiccs, 1 found roots equally 

 diseased to which no manure had been applied. In some experiments 

 instituted by his (Jrace the Duke of Bedford, which 1 have liad tlie iionour 

 to conduct, on the nature of salt as a manure, simple, and combined with 

 other substances, as stable-dung in ilifterent states, lime, soot, oil-cake, 

 &c., applied in different modes, and in various proj)ortions, to soils differ- 

 ing essentially from each other in their natural pro|)erties, as loams, sili- 

 ceous sandy soils, clayey soils, peats, and heath or moor soils, for the 

 growth of the different useful species of agricultural plants; the results, as 

 it immediately regards this particular affection of turnips, have not been so 

 ilecisive in favour of salt or lime as I had anticipated ; for the disease 

 appeared in every case, though in different degrees. Combinations of salt 

 and lime were evidently the most effecual, as no instance occurred of the 

 bulb being affected below the surface of the soil. That portion of it, how- 

 ever, which was above the surface was affected with galls, the same as in 

 the bulbs grown on soils of the same nature, to which no application of 

 manure had been applied. On a space of the same soil, to which salt 

 simply had been applied the preceding spring, and from which time the soil 

 remained fallow, the crop was good. One plant in ten, however, was 

 affected with the disease below the surface as well as above it. The salt 

 in this instance had been applied at the rate of 86 bushels per acre, and 

 mixed with the surface -iin. deep ; it was applied in the first week of May, 

 1818. On one portion of it barley and turnips were sown, but they did 

 not vegetate, the dose being too great. The season following, however, 

 the crops were good. On the same soil lime was applied at the rate of 

 120 bushels per acre, and the disease was not less general than in the 

 former case. Lime was applied to a clayey loam, and to siliceous sandy 

 soils, at the rate of 120 bushels per acre to 25, and salt from 80 bushels to 

 o per acre, but without any decisive effects in the prevention of this dis- 

 ease of turnips. The maximum and minimum of salt were here nearly 

 ascertained. In every distinct soil, the quantities applied were the same, 

 and the trials made imder the same circumstances. With regard to the 

 mode of applying salt and lime for turni|)s, that of niixing it with the soil, 

 previously to sowing the seed, or applying it to the surface alter sowing, 

 proved best ; for, when salt and lime are mixed, and deposited with the 

 seed, vegetation is retarded from two to twelve days, and more, beyond the 

 natural period. This fact was proved on the seed of eight different spe- 

 cies of plants, sown on four different kinds of soil. However beneficial, 

 therefore, salt or lime, in other respects, is to the soil (a subject not within 

 the j)resent enquiry), and though they seem, when combined, to modify 

 this disease, yet it appears they are not, either in a simple or combined 

 state, a specific remedy for this disease in turnips 



" I have procured seed from roots perfectly free from this disease, sowed 

 in a situation excluded from the neighbourhood of any other species or 

 variety of 7/rassica; which, when sown on land that, to niy knowledge, 

 never was sown w ith turnip seed before, and on old garden land, in both 

 cases produced bulbs more or less affected by this disease. Whether the 

 reverse of this takes place, I have not had an opportunity to obtain satis- 

 factory proofs ; and until the minute particulars of the economy or natural 

 habits of the insect, which is doubtless the innnediate cause of the disease, 

 is intimately known, it will be difficult to proceed in devising any plan of 

 prevention, with a hope of certainty of success. One point is clear and 

 evident, that whatever increases the vigour and rapid growth of the tiu-nip 

 plant, in its early stages of growth, checks with considerable force the pro- 

 gress and bad effects of this formidable disease 



" This disease appears to lessen the nutritive powers of the turnip, in 

 various degrees, according to its violence." 

 13 



