lyEAF Curl and Plum Pockets. 333 



were but a leaf form of E.farlowii if it were not for the fact that 

 I have observed two very different species of Exoascus growing in 

 very close proximity to each other on the same tree, so close in 

 fact that it is quite probable the mycelium of the two was inter- 

 mingled in the branch which bore the affected fruits and leaves. 

 These occur on Pnimcs americana under which paragraph the 

 description of the species will be found. Another reason for con- 

 sidering them distinct species is the probable fact that usually a 

 certain species quite constantly exercises a peculiar physiological 

 influence upon the host, and that if the form on the leaves and 

 twigs of P. sej'otina described here were the same species as 

 that which occurs on the fruit of the same tree, we would expect 

 it to produce a spongy abnormal growth in the buds and ends of 

 the branches just as Exoascus mirabilis Atkinson does in the buds 

 of Prumis augustifolia . For these reasons and from the fact that 

 the fungus departs too widely from the characters of Exoascus 

 deformans, it seems best to consider it as a distinct species, and I 

 propose the name E. varius for it on account of the variable pro- 

 portion which exists between the length of the ascus and stalk cell. 



Prunus maritima Wang. Beach Plum. 



Exoascus communis Sadebeck. 



This species affects the fruit of P. maritima, causing the plum 

 "pockets." The specimens which I have seen were collected by 

 Dr. Farlow at Dartmouth, Mass. ^adebeck* has recently 

 described this species as occurring on this host as well as on P. 

 pum-ilal^. and P. am.ericana Marshall, all from the United States. 

 The structure of the asci and the relation of the stalk cells to the 

 epidermis is represented in fig. 58. The asci are slender, rather 

 slightly clavate, and rounded or somewhat truncate at the free 

 ends. Sadebeck gives the measurements for the species as fol- 

 lows : The asci are 30-40 long and about 8 in diameter, the 

 stalk cells 15 to 20 high by 3-5 in diameter. Although the stalk 

 cells are often somewhat pointed below he says they do not 

 intrude between the cells of the epidermis. The measurements 

 I have taken from the asci on P. maritima vary but little from 



*Die parasitischen Exoasceen. Ab. a. d. Jahrb. d. Hamb. Wiss. Anst. X, 

 2, p. 47. 1893- 



