96 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



No systematic experiments liave been attempted in this country to 

 prove the general value and efficacy of the various fungicidal prepara- 

 tions which have been proposed from time to time by individual cul- 

 tivators for certain plant diseases. The general impression prevails 

 that sulphur is a universal panacea for all the ills, of a fungus origin, 

 that plants are heir to, but the value of this substance is limited to a 

 smalfgroup of these parasites, and here even its action is not always 

 certain. There exist prejudices, however, in favor of the use of sul- 

 phur as a fungicide which operate against the introduction and use 

 of other and more active remedies. There has been also a certain 

 feeling of indifference on the part of farmers and fruit-growers rela- 

 tive to this subject, doubtless due to the greatness of our country and 

 the variety of our resources, but more especially to the almost entire 

 absence of information respecting the nature and habits of the fungi 

 themselves. With increasing cost of production and greater compe- 

 tition the producer is feeling more and more keenly the losses which 

 diminish his profits; he has come to realize fully the gravity of the 

 ravages wrought by fungi, a fact well attested by the numerous let- 

 ters received from agriculturists and fruit-growers throughout the 

 country, earnestly asking information on this subject and the assist- 

 ance that will enable them to prevent the depredations of these para- 

 sites. 



The most important work of this section during the past season has 

 been the preparation of a special report (Bulletin No. 2) of the Botan- 

 ical Division, on the " Fungus Diseases of the Grape- Vine." In con- 

 sideration of the importance of the subject treated in this report, 

 together with the fact that the edition printed is already nearly ex- 

 hausted, it has seemed advisable to present here an abstract of some 

 of the leading topics discussed in it. 



I. — The Downy Mildew. 



Peronospora viticola, De By. 



(Plate I.) 



The Downy Mildew is common to both the wild and cultivated 

 grapes of this country, and from the former it doubtless was conveyed 

 to the latter in the earliest days of American gra^e culture. 



In some respects it may be deemed a more serious enemy to viti- 

 culture than Black-rot, for by its action on the leaves it affects the 

 nutrition of the vine, weakening the vitality of the latter and event- 

 ually destroying it. This action upon the leaves interferes with the 

 development of woody tissue in the growing shoots and prevents the 

 ripening of the fruit, and the wine produced will be inferior both in 

 quantity and quality. 



The Downy Mildew attacks all the green portions of the vine — the 

 leaves, young shoots, and berries — and is a true parasite, closly allied 

 to the fungus of the potato-rot. The fungus consists of a mycelium, 

 which grows within the tender tissues of the vines attacked, and of 

 the reproductive bodies or spores. 



The mycelium. — The vegetative portion, or mycelium, of the fungus 

 grows between the cells composing the tissues of the leaves, young 

 grapes, and shoots, never through them, and the threads, or hyphas, 

 of which it is made up, branch most irregularly and vary greatly in 

 diameter. These threads have no cross partitions, or septa, but are 

 continuous throughout their whole length, and are filled with a col- 



