18 MASSACHUSETTS HORTICULTURAL SOCIETY. 



These parasitic fuugi are very exclusive in their choice of a host- 

 _plant ; they are often limited to a single species, and generally to a 

 single genus. The potato " mildew," for example, attacks only the 

 potato and tomato ; the ' ' black-knot " occurs only on plum and 

 cherry trees ; one species of ' ' smut " only on onions ; another only 

 on cereals, and so on through the majority of species of parasitic 

 fungi. Were it not for this fact we might well despair of success. 

 Even as it is, there can be no question that the number of plant 

 diseases has increased alarmingly within the past twenty or even 

 ten years. Many of you remember when there was no such thing 

 in this neighborhood as potato " rot," and the potato crop was far 

 superior, both in quantity and quality, to what it is today. Ten 

 years ago Delaware, New Jersey, and even Connecticut could 

 compete successfully with the product of any peach-growing 

 region ; today, in places, the peach industry has been almost 

 ruined by "yellows," and what fruit gTows is of poor qualit}'. 

 Last year one-fifth of the oat crop of Idaho, valued at more than 

 $120,000, was destroyed by " smut," and any of our crop reports 

 will show us similar figures much nearer home. These are serious 

 facts, but still, I think neither inexplicable nor wholly beyond our 

 control. The increase in the number of fungous diseases may be 

 due to one or more of many causes. It may be that distinct 

 species of parasitic fuugi, hitherto unknown to science, have 

 appeared upon our cultivated plants — new species in the sense that 

 they have been studied and named within the memory of the 

 present generation. No doubt such species existed previouslj^, 

 but the number of expert specialists in this wide field of botany 

 was very small twenty-five years ago, and the means of investiga- 

 tion comparatively inadequate. As an illustration of the rapid 

 growth of botanical knowledge in this direction, it is striking to 

 observe that a work recently published gives descriptions of 

 39,663 species of fungi, as compared with 11,893 species known 

 in 1862, and that duriug the present year no less than 1,500 new 

 species have been discovered. It must be remembered that the 

 majority of these " new species " are merely imjoerfect, or form- 

 species, and as their life-history becomes known will be denied 

 specific value and placed under the name of their respective 

 perfect forms ; also that very few of them are parasitic, and hence 

 of economic importance; nevertheless there can be no doubt that 

 this cause has much to do with the increase in the number of 



