32 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



The washing of the whole of the inside of the greenhouse with 

 carbolic (i in 8) after the removal of the top soil involves the wash- 

 ing of the subsoil which has been penetrated by the roots of the 

 tomatos. Less than J gallon to the square foot of subsoil surface 

 would be out of the question, and the treatment of I acre of 

 subsoil at J gallon to the square foot with carbolic acid (i in 8), 

 "liquid carbolic acid" being sold at 3s. per gallon, would cost 

 £4,840 X 9 X i X J X 3/20 =£408 75. 6d. 



Of course such treatment is permissible on a small scale, and the 

 recommendation answers admirably where the grower takes things 

 in time and stamps out the disease thereby on its first appearance. 

 But where, as in many nurseries, the disease has spread over a large 

 number of houses the method above advocated becomes rather costly. 



It should be borne in mind also that a large number of proprietary 

 substances are on the market, by the application of which in rather 

 small quantities the makers and vendors claim that the disease in 

 question can be eradicated. For example, the directions for use given 

 with one of these substances may be summarized as follows : 



" Apply a solution of 1 in 40 at the rate of J gallon per square 

 yard." 



Taking the price at, say, 2s. a gallon, the cost for an acre is 

 2S. x 4,840 x i X 1/40 = £6 is. At 5s. a gallon the cost would be 

 only £15 2s. 6d. 



Another substance, " for badly diseased soil," is advised at a 

 strength of 1 in 64, one gallon of solution to the square yard, the price 

 being, say, 2s. a gallon. The cost is only 2s. x 4,840 X 1/64 = 

 £7 us. 3d. an acre. 



Furthermore certain growers who have tried one or other of these 

 substances have expressed the opinion that the results were salutary. 

 Such being the case, the huge disparity between the cost of a pure 

 carbolic acid treatment and that of the substances just referred to is too 

 great to be ignored, at any rate by a tomato-grower. His disposition 

 is such that he will not have an experimental plot — even if at some- 

 body else's expense — involving a cost of £980 an acre. On the 

 other hand, he will shoulder a £6 an acre outlay with comparative 

 joy, even if the joy is somewhat tinged with scepticism. 



The leaflet (No. 75) referred to above also recommends (2) an 

 intimate mixture of the soil with gas-lime. As gas-lime is not now 

 on the market because of the substitution of " oxide " for the quick- 

 lime in gas works, this recommendation is not now a practical one. 

 Naphthalene and sulphate of potash are also mentioned. 



As not all proprietary sterilizers are composed of carbolic 

 acid, sulphate of potash, and naphthalene, it is evident that there was 

 room for experimentation with a variety of likely soil sterilizers ; so 

 trial plots with twenty-six different substances were laid down in 

 19*5. 



The houses in which the experiments were carried out were all 



