THE FUNGI WHICH CAUSE PLANT DISEASE 247 



Conidia (=Diplodina citrullina) Pycnidia similar to the peri- 

 thecia, spores 2-celled, hyaline, straight or curved, more or less 

 cylindric, 10-18 x 3-5 /*. 



The fungus was isolated in pure culture by Grossenbacher ^"^ 

 from muskmelons by direct transfer of diseased tissue to potato 

 agar. Inoculations from these cultures proved the fungus capable 

 of entering healthy uninjured tissue, the 

 disease showing about six days after in- 

 oculation. The brownish pycnidia origi- 

 nate from an extensive subepidermal, 

 partially cortical, much-branched, brown- 

 ish myceUum but soon break through and 

 appear almost superficial. When mois- ^'°eri\fecTum-anS: a1: 

 tened, spores issue in coils. Darker peri- *®'' Klebahn. 

 thecia, nearly superficial, are found on old diseased spots. Both 

 ascospores and conidia are capable of causing infection. Inocu- 

 lations on pumpkin and watermelon gave positive results; these 

 on cucumber, West Indian gherkin, squash, pumpkin, and gourd 

 were negative. The same fungus has been reported as cause of 

 canker of tomatoes.^ 

 M. tabifica (P. & D.) Johns.^-*'" 



Perithecia rounded, brown; asci oblong-clavate, 8-spored; spores 

 hyaline, upper cell larger, 21 x 7.5 /x. 



Pycnidia (=Phoma) subglobose; conidia elliptic, hyaline, 5-7 x 

 3.5 fi, escaping as a gelatinous cirrus. 



This conidial form, common on beets causing leaf spot through- 

 out the summer, is said by Prillieux and Delacroix to be connected 

 with M. tabifica the perithecial form, which is found upon the 

 dead petioles at the end of the season. Convincing evidence^ of 

 this connection seems wanting. The conidial stage ^"^ is variously 

 known as Phoma betas, Phoma sphserosperma, Phyllosticta 

 tabifica. The Phoma-form from stems and rotten roots and the 

 Phyllosticta-forms from leaves were both studied by Hedgcock ^"' 

 in pure cultures on many media and many inoculations were made, 

 all leading to the conclusion that the Phoma and the Phyllosticta 

 are identical. 

 M. tulasnei Jacz.^" 

 Perithecia subglobose, minute; asci cylindric fusoid; spores 



