152 ASCOMYCKTIX 



The Eroa'sccac may be grouped, according to the symptoms 

 of the disease produced, as follows ; for this purpose we shall 

 class all the species as one genus, ' Exoascus ' (or Tallinn a): 



I. Species which cause deformation of the ovary or other part 

 of the fruit. 



E. pruni (Fuck.) on Prunus (Jomcsfica, P. Padus, P. rir- 



giniana. 



E. Rostrupianus (Sad.) on Primus spinusa. 

 E. communis (Sad.) on Prunus pumilla, P. maritima, P. 



iiiyra, P. tiiiicririniii. 

 E. Farlowii (Sad.) (E. varius, Atk.) on Prunus serotim/, 



causing also deformation of twigs. 

 E. lonyipes (Atk.) on Prunus americana. 

 E. confusus (Atk.) on Primus virginiana. 

 E. rhizipes (Atk.) on Prunus triflora. 

 E. cecidomophilus (Atk.) on insect-galls on the fruits of 



Prunus virginiana. 

 E. mirabilis (Atk.) on Prunus angustifolia, P. liortulana, 



P. americana. 

 [Also species on Prunus subcordata, P. CMcasa, and P. 



pennsylvanica.] 

 E. alni incanac (Ktihn) (E. amcntorum, Sad.) on Alnus 



incana. 



E. alni ylutinosac (Tubeuf) on Alnus ylutin<>*<i. 

 E. Robinsonianus (Giesh.) on Alnus inca/i/i. 

 E. Johansonii (Sad.) on Po'puhis trcmnla, P. tri'iimloidcs, P. 



grandidentata. 

 E. rhiwpliont* (Johan.) on Popuh's ll>n. 



II. Species which (1) produce witches' brooms, or (2) at least 

 cause deformation of shoots ; asci produced on the leaves. 



(1) E. cpipliyllns (Sad.) (E. l>orcaUs, Johan.) on Alnus 



incand (uniform grey coating of asci on both sides 



of leaf.) 

 E. turf/ ii/ us (Sad.) on Bctula ro-rueosa (coating of asci on 



under surface accompanied by slight crumpling of 



leaf). 

 E. betulinus (Kostr.) on Bctula puli-^rns and B. odorata 



(coating of asci on under surface). 



