20 PLANT DISEASES AND FUNGI. 



estimated at about one-sixth of the crop. In Maine the reporter 

 says : " I call to mind one season when we lost more than half our 

 crop, about mid-winter, by rotting. The apples began rotting under 

 the ' scab ' spots, and eventually the fruit entirely decayed." This 

 same " apple scab " is destructive in our own orchards, but to what 

 extent no one has taken the trouble to inquire ; and in the Australian 

 colonies it is another of the foes with which the cultivator has to 

 contend. 



In countries where the cultivation of the grape-vine is of com- 

 mercial importance, vine diseases, apart from the Phylloxera, cause 

 immense injury. The Commissioner of Agriculture in the United 

 States reports : " In my opinion, which is based upon special reports, 

 and on other available and trustworthy information, the annual loss 

 from ' grape rot ' during the last ten years, in the principal vine- 

 growing regions of the United States, has not been less than one- 

 fourth of the entire crop."^ Again, a reporter from Ohio states that : 

 " In years past grape rot has destroyed hundreds of tons of grapes 

 here, so that nearly every vineyard has been dug up. I have seen 

 the produce of whole vineyards destroyed in three or four days." 

 And yet this is but one of the many diseases of the vine, and is not 

 the same with the white American mould which is finding its way 

 into Europe. 



Details are unnecessary of the damage done to other important 

 crops, which are now matters of history, such, for instance, as the 

 widely-spread potato disease, of which we have had a plentiful 

 experience here and in Ireland ; of the coffee disease which ruined 

 the plantations in Ceylon, and brought the planters to despair ; of 

 the disease which fell upon the opium poppy in India, and at once 

 reduced the area of cultivation ; of the damage sustained by the 

 cocoa-nut palm in tropical South America and the West Indies ; and 

 even of the larch disease, which has long been a terror in Northern 

 Europe and in Scotland. In all these cases the pecuniary loss must 

 have been enormous, and more than enough to justify the demand for 

 a closer and more systematic investigation into the history and 

 mystery of plant diseases, with a view to their remedy. 



At the outset of this inquiry we are met by the general question 

 of the causes of disease in cultivated plants, and are compelled to the 

 confession that there are several primary causes, of which parasitic 

 fungi is but one, although one of the most important. Another is due 



2 "Report to Commissioner of Agriculture," Washington, 1886. 



