NORTH AMERICAN PARASITIC PZXOASCE^. 



91 



B. The nncelium is perennial in the buds of the liost- 

 plant and develops, at the time of new growth in the young 

 leaves, only between the cuticle and epidermal cells. Branch 

 distortion and -'witches' broom*' formation present. 



1. Asci \\\\\\ stalk-cells. 



Exoasnis dcforuuiiis^ ( Berk, j Fuckel. 



2. Asci without stalk-cells. 



a. On foliage leaves. 



Exoascns barter iospcnum (Johans.) Sadeb. 



b. On floral en^'elopes. 



Exoascus auicntornin Sadeb. 



C. The resting mycelium spreads intercellularly, causing 

 distortion of the leaves. [No American form. | 



TAPIIRINA Fries. 



A mycelium perennial in the host-plant does not occur. 

 The continuance of the species is insured only by the infec- 

 tion of the spores. After the germination of the spore a 

 sub-cuticular mycelium develops, which spreads over a larger 

 or smaller part of the leaf and very soon, in a succession 

 of a great number of swellings and protuberances, part apical 

 and part lateral, the hyphii? are differentiated into a fertile and 

 sterile part. The fertile hypha^ develop, on taking up rich 

 nourishment from the host-plant, into the hymenium, while 

 the sterile remaining part gradually loses its contents, becomes 

 shiny, and finally entirely disappears. The entire sub-cutic- 

 ular mycelium is not used up in the formation of the asci. 

 The external visible signs of disease are limited to larger or 

 smaller spots on leaves, only Taphn'nopsis. causing irreater dis- 

 tortion. 



^'I. The mycelium and the Inmenium formation is always 

 sub-cuticular ( Entaphriua ) . 



I. The fertile hypha? are entirely used up in the formation 

 of the asci. 



