11 



leaves spots very similar in outline and appearance to those caused 

 by xllternaria vlolm (with which they are often confused), but in the 

 writer's experience in the study of the violet and its diseases he does 

 not recall a single instance where these fungi have come to his atten- 

 tion as causing any serious trouble. It is possible, however, for them 

 to do considerable damage under conditions peculiarly favorable to 

 their development. 



Ninety-live per cent of all the specimens of the .so-called violet disease 

 received at the Division laboratory during the past four or five years 

 were found, upon careful microscopical examination, to contain spores 

 of the particular fungus mentioned.' 



The fungus was isolated by agar poured cultures in Petri dishes, and 

 comparatively little difficulty was experienced in securing pure cultures 

 for inoculation experiments. The growth and development of the fun- 

 gus on artificial media is, as a rule, quite rapid, normally producing 

 spores in from four to six days after the sowing of the spores or the 

 transferring of a single germinating spore from one plate culture to 



another. 



The growth of the fungus in agar is normally in concentric rings, 

 each ring marking the amount of growth made in twenty-four houra 

 (PI. V, fig. 1). The color of the fungus growing on agar before spore 

 formation is grayish white (PI. V, fig. 3). Spore production begins 

 at the center on the older growth, and gradually extends outward, 

 until the entire surface of the colony is covered with a dense mass of 

 olivaceous spores. The fungus grows well on other culture media, 

 especially young lima bean pods (PI. VI, fig. 18). 



The first inoculation experiment with Alternaria molce was made 

 February 12, 1896. Two plants of Marie Louise violet, in 4-inch 

 pots, were removed from the Department greenhouse to the labora- 

 tory. They were quite uniform in size and, as far as could be ascer- 

 tained by observation, entirely free from disease. Plant No. 1 was 

 sprayed with sterile distilled water and placed under a bell jar in a sat- 



^ SCIENTIFIC DESCRIPTION OF THE FUNGUS. 



Alternaria violse Galloway and Dorsett. 



Amphigenous, but especially epiphyllous, olivaceous, velutinous, on light-colored 

 subcircular definitely limited spots 2-4 mm. in diameter, extending into arid 

 patches 10-12 mm. in diameter, which show one or more dark concentric lines; 

 spore-bearing hyph?e fasciculate, erect, pale olivaceous, septate, simple, 4 l)y 25-30 a; 

 conidia borne at or near tips of the hyphte, catenulate, clavately Hask-shapcd, 

 muriform, strongly conHtricted at the septa, which are variable in number, oliva- 

 ceous, 10-17 l)y 40-60 /.i exclusive of istlnnus, which is 3-5 by 3-25 //. 



Dr. Gino Pollacci has described and figured (Atti del K. Inst. Bot. dell'Univ. di 

 Pavia (Laboratorio crittogamico) Ser. II, Vol. V, pp. 1-2, PI. VII, figs. 1-5, 1897) 

 a spot disease of violet occurring in Italy which is due to a fungus which he names 

 }f(icnjspnriiiiri rlolir. If his description and (h-awingsare correct the two diseases are 

 quite distinct. 



