172 MASSACHUSETTS AGRICULTURE. 



In speaking of the means of checking the disease, we must 

 necessarily consider two questions : first, is the smut prop- 

 agated by the onion-seed ; and, secondly, is it brought on 

 by the exhaustion of the soil by continued crops. With 

 regard to the first question, we can state that there is very 

 little chance of the smut being propagated by seed. Very 

 few of the plants affected by the disease ever ripen seed, and, 

 of the seed-plants, the fruit does not ripen until the smut has 

 mostly disappeared from neighboring plants, so that there is 

 little chance of the ripe seeds having the spores of the smut 

 blown upon them. It would be well to let the seed soak in 

 water for some hours, that if by any accident any spores are 

 adhering to them, they may be washed off. With regard 

 to the second point, without losing sight of the fact that a 

 feeble plant is more likely, in general, to contract any disease 

 than a thrifty one, it is certain that no amount of exhaustion 

 of the soil will bring on the smut unless the spores of the 

 Urocystis are present, and, if the spores are present, the smut 

 will follow, no matter how good the soil. So far, the object 

 of the onion-raiser has been, by a change or increase of fer- 

 tilizers, to try to get rid of the disease. This is a mistake. 

 The thing is not to introduce any new substance into the soil, 

 but to get rid of something which is already there ; viz., the 

 spores of Urocystis Cepulce. Nothing which can be put into 

 the soil in the way of manure is at all likely to kill the spores. 

 A glance at fig. 5 will show that the spores of the onion- 

 smut fungus are extraordinarily well protected ; in fact, there 

 are scarcely any spores of fungi so well protected as those of 

 the species of Urocystis. A comparison of fig. 5, which 

 represents the spores of the onion-smut, with fig. 6, which 

 represents those of the corn-smut, will show why the former 

 should be more difficult to destroy than the latter. Besides 

 the tough nature of the spores proper, they are surrounded 

 by a layer of tough cells already described as accessory spores. 



The expression used by all persons with whom we have 

 corresponded in relation to the smut, that the disease is in the 

 ground, is well founded. The disease, — that is, the spores of 

 the fungus, — is in the ground, and there it will stay unless 

 removed mechanically, for no substances which can be used at 

 all as manure can be expected to destroy it. Theoretically, 



