656 THE GENUS CONIOTHECIUM . 



The Phoma pycnidia, judging by the spore characters, evidently 

 belong to Phoma mali, Schulz & Sacc. The spores are hyaline, 

 unicellular, biguttulate, straight to slightly curved, and measure 



5.6 to 7.36 X 2-76 to 3.8 /x. 



The pycnidia formed on media are usually circular or sub- 

 circular, and often more or less aggregated together (PI. 34, e). 

 Depressed pycnidia, more typical of Phoma iiiaH. liave also been 

 observed. 



Summary and Conclusion. 



The paper contains certain cultural characters of Coiiio- 

 thecium chomatosponiiii, Corda, isolated from diseased apple- 

 twigs, where the fungus j^roduces a blister disease. On the fruit 

 the fungus causes " russeting," and if infected while young, the 

 fruit cracks, or under certain conditions Vvathers and dies. 



The fungus also occurs on the branches of pear trees, and 

 isolation yielded results agreeing well with that described for the 

 apple. 



The Coniothcciinii developes between the cells. It invades 

 the middle lamellae, and as a result the cells separate, thus ulti- 

 mately ruptiu'ing the skin and producing blisters or russet mark- 



ings. 



The cracking of the fruit, caused by infection with this 

 fungus, must not be confused with cracking brought about by 

 physiological causes. 



The organism was isolated in 1913, and Phoma pycnidia 

 formed abundantly in the original culture. Subsequently, by 

 SfOwing only the Phoma spores, evidence was obtained that the 

 Coniothecium condition is only a stage in the life cycle of the 

 former — a view also advanced b}' Massec. 



The cultural characters have much in common with those 

 of Coniothecium amcutaceaniiii. Corda. as described b}' Gue- 

 guen, and had the investigation been completed, probably fm'ther 

 resemblances would have come to light. 



The Phoma which (leveloi)ed in cultures is Phoma iiiali. 

 Schulz & Sacc, and hence Coniothecium chomatosporum. Corda. 

 must be regarded as but a stage in the life circle of Phoma mali. 

 thus agreeing with the view of Massee. 



Our present knowledge of the genus CouiotJiecium does not 

 warrant us to conclude that all the Coiiiotlicciiims will uhimately 

 be related to the genus Phoma, and the subject is well wortii 

 further detailed investigation. 



The Phoma pycnidia have also l)een observed on the host 

 plants, though the Coniothecium stage is the more common in 

 this country. The ascigerous stage — Diaporthc ambigua. Nits. — 

 reported by Massee. has thus far not come to the notice of the 

 writer. 



The paper contains references to previous work as complete 

 as possible ^I'om the publications at the disposal of the author, 

 and for further references the reader is referred to Gueguen's 

 work quoted. 



