THE DIRECT CAUSE OF TEACH LEAB" CURL. 31 



TlIK FUNGUS CALSINO THE J)1SEASK. 



The fungus causinijf poach k^af curl, now known as E.i'o<i.snis (Icforinans 

 (U(>rk.) Fuckel, is a incnil)cr of tlie sul)faiuil3' of fungi known as 

 Ki-ixixouv. The ^i^Y>r^y6V'^^ are low or simple Aiicomi/cete-s^ov fungi l)ear- 

 ing their spores in cases or asci. 



The classification of the Exoanceiv, which now lays greatest claim to 

 scientific permanence is that outlined in the recent writings of Sade- 

 beck, who has given careful study to these forms.' 



Of the five genera which he recognizes, onlv the last directlv concerns 

 us at this time, as it is to this genus {Exoascus) that the peach curl 

 fungus belongs, as well as numerous other species injurious to horti- 

 culture. In considering this genus Sadebeck" has grouped thirty of 

 its species according to certain characters of development. He recog- 

 nizes the following characters of the genus: 



Exoascus Fuckel. 



A. The inycelimn is perennial in tlic inner tissues of the axial organs. 



(t. Tlie development of the liynieniuni occurs only in the floral leaves of the 

 host plant. Eight species. 



1). The development of the; hymenium occurs only in the f(»liagc, leaves of the 

 host plant. Seven species, including E. (h'formans.^ 



c. The development of the hymenium occurs upon tin- leaves as well as upon the 

 fruits. One specie's. 



B. The mycelium is perennial in the buds of the host plant and develops only 

 subcuticularlv in the leaves. 



^Sadebeck, Dr. R., Die parasitischen Exoasceen, Hamburg, 1893, p. 43. 

 Sadebeck recognizes five genera in the Exoascex, which he arranges and character- 

 izes in the following manner: 



EXOASCEA'J : Ascomycetes whose asci are not united in a fruit body. 



A. The asci arise as swellings at the end of the Ijranches of the mycelial 

 threads. 



1. Endoinyces Tulasne. Four-spored asci, no conidia within the same; the sterile 

 threads develop chlamydospores and oidia. 



2. MagnimcUa Sadebeck. Parasitic. Asci with more than four spores; usually 

 conidia formations in the ascus. Oi'dia and chlamydospores wanting. 



B. The asci take their origin from a more or less loose hymenium. 



3. Ascocorticium Bref. Saprophytic on bark. The ascus layers are arranged in a 

 loose hymenium upon the mycelium. 



4. Taphriita Fries. Parasitic. Without perennial mycelium. In the formation 

 of the ascogenous cells differentiations of material occur. Forming leaf spots.' 



5. Exonscvf^ Fuckel. Parasitic. With i)erennial mycelium. In the formation of 

 the asci no differentiations of material appear. The subcuticular mycelium changes 

 directly to ascogenous cells. Causing sprout deformations. 



^Sadebeck, Dr. E.., Einige neue Beobachtungen und kritische Bemerkungen iiber 

 die Exoascacese, pp. 277,278, reprint from den Ber. d. deutsch. bot. Ges., 1895, 

 Bd. XIII. 



^Dr. von Derschau has described the occasional fruiting of Exoaseus deformans in 

 the blossoms of the peach. The figures given by this author do not show the nor- 

 mal development of ascogenous cells in the blossoms which are so common in the 

 leaf blade of the j)each. His figures show the asci as arising from lateral branches 

 of a continuous mycelial hyplia, and this mycelium is situated beneath the epidermal 

 cells instead of between the cuticle and epidermis (Landw. Jahrb., Berlin, 1897, pj). 

 897-901, and Table XLI) . 



