336 Bulletin 73. 



oval, agreeing in this respect somewhat with the spores of Exoas- 

 cus rost7-upia7ius'^ Sadeb. but not so large as in that species. 



The mycelium is very abundant in the tissues of the aflfected 

 buds, Jorming a very complex network of threads between the 

 cells of the hypertrophied tissue. The details of structure are 

 shown in figures 61 and 62. 



The same fungus also occurs in Iowa, specimens collected on 

 Primus angustifolia (P. chicasa) in Chickasaw Co. , by Prof. L. 

 H. Budd, were communicated to me by Prof. ly. H. Pammel. 



The mycelium is perennial in the branches, and in the follow- 

 ing spring the young buds from such branches are more likely to 

 suffer from attack. 



Exoascus mirabilis var. tortilis n. var. 



This form occurs on the fruit of Prunus angustifolia , very rarely 

 producing the plum " bladders," and then the fruit is only affect- 

 ed on one side and is strongly curved. Usually the attack is con- 

 fined to a rather small area or so small that a considerable portion 

 of the fruit retains its normal form and color, and it is not hollow 

 within. The structure of the fungus is but little different from 

 that on the buds, the chief differences being in somewhat larger 

 development, so that the asci are somewhat longer and the stalk 

 cells higher. The other characters, including those of the my- 

 celium are the same as in the form on the buds. The propriety 

 of separating the form on the fruit as a variety may be questioned, 

 but it seems well to do so in order to avoid possible confusion, 

 since the form on the buds is the more common one in localities 

 where I have observed it, and quite frequently trees may present 

 many buds which are affected when all the fruits are free from 

 attack. 



Erwin Smitht notes the occurrence of both these forms on P. 

 angiistifolia and its cultivated varieties in Maryland and Georgia. 

 He suggests that it may be distinct from the E. pmni. 



Many of the native trees are very seriously affected, and it 

 seems in some cases to be spreading and becoming serious in the 

 plum orchards in the southern states. 



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

 I, p. 46, 1893. 

 tjour. Mycology, p. io8, vol. VI. 



