THE FUNGUS CAUSING THE KOT, 27 



ti\ I' in New Jersey, it has also been found in West Vir<2:inia. Massachu- 

 setts, Wisconsin, and Xova Scotia. 



THE FUNGUS (ACANTllOKIlVNCin S VACCINII. SIIKAr) CAUSING THK ROT. 



The fungus producing the rot differs in several resi)ects from any 

 species which we have been able to find described. The rarity of its 

 occurrence in a fruiting condition in the field probably accounts for 

 its not having been discovered before. It has been found occasion- 

 ally in considerable (quantity on fallen leaves of diseased vines, and 

 frequently appears on apparently healthy leaves from diseased 

 vines whit;h are kept in a sterile moist chamber for a week or two. It 

 grows readily on various culture media and produces an abundance 

 of ascogenous perithecia. 



Ascogenous form. — The perithecia aiv oi-dinarily sparsely scat- 

 tered over the under surface of the leaf, being buried beneath the 

 epidermis, Avhich is very slightly elevated and punctured l)y the short 

 neck and ostiole (PI. Ill, fig. 12). They usually vary in diameter 

 from 300 to 400 /x. The short neck of the perithecium is beset with 

 black, nonseptate spines 50 to TO fi long by 8 to /x thick at the base. 

 These black spines are a constant and characteristic feature of the 

 fungus, occurring in all of our cultures, as well as under natural 

 conditions (PI. Ill, fig. 13). On leaves the perithecia are somewhat 

 depressed globose, but in artificial cultures, where there is no 

 l^ressure from above as there is in the tissue of the liost, they are 

 somewhat pyriform. The Avail of the perithecium is membranous or 

 submenbranous in texture and consists of a single layer of cells. Tlie 

 asci are clavate, short-stipitate, and range in size from 136 to 180 by 

 30 to 48 fx. They are accompanied by rather stout, sepate paraphyses, 

 occasionally branched mwr the end and varying in dimensions from 

 200 to 340 by 5 to 8 /t. The ascospores are somewhat biseriate or 

 irregularly uniseriate. They are hyaline until almost mature, but 

 finally assume a pale yellowish brown color. In shape they are 

 oblong elliptical, and the protoplasm is densely granular. They vary 

 in size from 27 to 36 by 12 to 20 /x. 



Fruiting specimens on leaves have been collected in May, July, 

 August, September, and October, and have been found in Xova 

 Scotia, Massachusetts, Xew Jersey, West Virginia, and Wisconsin. 



Xo conidial or pycnidial form of this fungus has ever occurred in 

 any of our numerous cultures, and no such form has been found asso- 

 ciated with it in nature under such circumstances as to suggest a 

 genetic relation. 



Appressoria. — A rather remarkable body is produced by the germ 

 tube of the germinating spore. This is a more or less disciform, 

 dark-colored, rather opaque organ, w-ith an irregular, rather deeply 

 110 



