202 Pflanzenkrankheiten, 



it occurs on leaves, it frequently causes distinct spots as well as 

 lesions on the green stems and pods. Later ihe same plants bear 

 an Ascomycete closely related to Sphaerella tierviseda var. microspora 

 Sacc. which is by the author named Mycosphaerella ontarivensis. 

 The Mycosphaerella and the Ascochyta are stages in the life history 

 of the same organism, because: 



1. The Mycosphaerella follows the Ascochyta in the field. 



2. The ascospores when planted in nutrient agar give rise to 

 an ascochyta which is capable of infecting the host plant. 



3. The infected areas develop typical Ascochyta like the plants 

 in the field, and later these same diseased areas develop a Myco- 

 sphaerella indistinguishable from the original material. 



4. Plants inoculated with ascospores directly develop first the 

 typical Ascochyta and later the Mycosphaerella. 



5. In all cases the check plants remamed free from disease. 



In his experiments the author found the time between inoculation 

 and the formation of the perfect stage in Mycosphaerella pinodes 

 about three or four months and in M. ontarivensis about two and a 

 half or three months. In the field these fungi develop their perfect 

 stage alter a period of one or two months of saprophytic existence 

 at a temperature of 60 to 70° F or higher. Therefore the author thinks 

 that our idea that the Sphaeriales having a parasitic conidial stage, 

 require the variations of temperature and factors attendant on a 

 Winter season in order to develop their perfect stage, is not well 

 founded. M. J. Sirks (Haarlem). 



Tolaas, A. G., A bacterial disease of cultivated mush- 

 rooms. (Phytopathology. V. p. 51—54. 1915.) 



In the mushroom caves in and around St. Paul, an unsightly 

 Spot on mushrooms is very prevalent. The severity of the Spotting 

 varies considerably on the different cultivated varieties, those most 

 badly affected being the large white varieties. Very often the spots 

 first appear when the mushrooms are in the early button stage, 

 while in other instances they do not appear before the fruiting, 

 body has attained a considerable size. Önly small areas may be 

 discolored, or the entire cap and even the gills may te involved. 

 At first the spots are pale yellow in color, but they finally become 

 a rieh chocolate brown. 



The discoloration does not extend far into the fruiting body, 

 the most severe cases observed showing the brown color but 3 or 

 4 mm. below the surface. The area in the immediate vicinity of this 

 dark discoloration is usually yellowish white in appearance, but in 

 cases where the attack is not so severe, the flesh remains perfectly 

 white. The disease reduces crop yiQld but little, but the value of 

 spotted mushrooms is, nevertheless, considerably diminished. 



Microscopic examination and poured plates, as well as tissue 

 cultures, show that bacteria are constantly associated with the disease. 

 The organism most constantly present, has proved to be the only 

 pathogenic form. It takes the group number 221 .2333133. This cor- 

 responds to the group number of B. ßuorescens except for the fact 

 that in dextrose broth the reaction is acid instead of alkaline. 



Fumigating the caves and beds with sulphur before planting 

 the spawn, seenis to be the only one practicable mean for Controlling 

 the disease; spraying with Solutions of coppersulphate, sodium car- 

 bonate and benetal in various strengths did not obtain any result. 



M. J. Sirk.«} (Haarlem). 



