Botany and Zoology. 415 



Europe and Madeira, and which is " the conidial form of some 

 species of the Ascomycetes, probably some Erysiphe,'"' although 

 supposed to have come from America,' is not a common or conspicu- 

 ous infestor of our native vines ; but that the commonest, at least 

 in New England, is Perenospora viticola, which is limited to the 

 leaves and stems, and does not attack the fruit. Being often 

 found on every leaf, of a vine, it would be expected to injure the 

 grape crop. " Such, however, is not the case. The fungus does 

 not attack the grapes themselves, nor does it, at least in New 

 England, appear until about the first of August, and its withering 

 effect upon the leaves is not very evident before September. As 

 far as out-of-door grape culture in the northern States is concerned, 

 we are inclined to believe that, practically, no harm is done by 

 Perenospora viticola^ but that, on the contrary, the fungus is 

 really beneficial. Our native vines have a luxuriant growth of 

 leaves ; and the danger is that, in our short summers, the grapes 

 may not be sufficiently exposed to the sun to ripen. But the 

 Perenospora arrives, with us, at a time when the vine has attained 

 its growth for the season, the important point being then to ripen 

 up the grapes which are concealed by the foliage. By the shrivel- 

 ing of the leaves, the Perenospora enables the sun to reach the 

 grapes without loss to the vines, as is shown by the fact that the 

 vines continue to live on, year after year, without apparent in- 

 jury." The botanical history, literature, and forms of this fungus 

 are fully illustrated, two plates show the structure and fructifica- 

 tion of this and some allied species; and a synopsis of the half- 

 dozen species of Perenospora detected in the 'United States, and 

 five of Cystopus, is appended. 



List of the Fnngi found in the vicinity of Boston. Confined 

 to the species which have come under the author's own observa- 

 tion. 



The Black Knot (of Plum and Cherry trees). This interesting 

 and important memoir is illustrated by three beautiful plates, 

 showing this disease in various stages, and the whole structure, 

 development and fructification of Sphoria mortosa of Schucinitz, 

 the fungus which produces this black knot, wliich so deforms and 

 injures plum and cherry trees throughout the Northern States and 

 Canada. The remedy is the knife or the axe. For prevention Dr. 

 Farlow recommends the extirpation of choke cherry trees, upon 

 which the pest largely breeds in the vicinity of Boston. Farther 

 west it would all the more be necessary to destroy all the wild 

 plum-trees (Prunus Americana), which are fearfully infested. 



N"o. 25, the last paper of the 'volume, is Prof. Sargent's 



Report of the J)irert<rr of the Arnold Arboretum ; — from which 

 we learn that: " Probably over 100,000 ligneous plants have been 

 raised during the nine months," and as many as 5,542 trees and 

 shrubs have'been presented to various establishments and indi- 

 viduals throughout the United States interested in agriculture," 

 besides those sent to Kew and elsewhere abroad. A catalogue of 

 the species raised is appended. a- «• 



