Nov. IS. 191S Sclcrotinia Spp. on Ginseng 293 



During a rainy period infection is evident within a much shorter time. 

 All attempts to produce the disease without previously injuring the 

 root gave negative results. 



IDENTITY OF THE SPECIES 



In order to further prove that the species of Sclerotinia from ginseng 

 is identical with Sclerotinia liheriiana Fuckel, a comparison was made 

 with cultures from different sources. In addition to the four strains 

 mentioned above, there was also used a pure culture isolated by Dr. 

 Donald Reddick, of Cornell University, from celery. The comparison 

 of the strains consisted in (i) growing the cultures on different media, 

 both acid and alkaline; (2) production of apothecia, measurements of 

 asci, ascospores, and a study of the manner of germination; (3) cross- 

 inoculations on lettuce. These topics are briefly discussed in the follow- 

 ing paragraphs. 



Growth on different media. — Cultures were made on potato agar, 

 nutrient agar, bean plugs, ginseng stems, and Raulin's synthetic fluid. 

 In the case of potato and nutrient agar both acid and alkaline media 

 vrere used (±10.5 Fuller's scale). On all the media the various strains 

 made a good growth, but no differences were visible. 



Production op apothecia, etc. — In order to obtain apothecia from 

 the various strains, the sclerotia produced in pure culture were placed on 

 sterile moist sand in dome-shaped preparation dishes. The sclerotia 

 were covered with a very thin layer of the sand, and the dishes were 

 placed on a shelf in front of a window. The time required for these 

 apothecia to develop varied greatly, the limits being from three weeks 

 to three months. The size of the apothecia likewise varied even in the 

 case of sclerotia from the same strain and produced in the same test 

 tube. However, the apothecia were alike in general appearance in all 

 the strains. Plate XXVIII, figure 3, shows apothecia from the celery 

 strain, and Plate XXVIII, figure 4, shows the same from the ginseng 

 strain. A large number of measurements made of asci, paraphyses, 

 and ascospores showed no marked variations, and agreed with the 

 description of Sclerotinia libertiana Fuckel as given in Saccardo. In 

 figure I, A, is shown a camera-lucida drawing of asci, ascospores, and 

 paraphyses from a fresh preparation of the Mentor strain. 



Crushed pieces of apothecia were placed in drops of water in order to 

 observe the ascospore germination. Within four hours after being placed 

 in water the first signs of germination became visible. Figure i , B, shows 

 the ascospores within the asci, germinated by sending germ tubes directly 

 through the walls of the ascus. No differences were noted in the germi- 

 nation of the spores from the different strains. 



Inoculations on lettuce. — Mature lettuce plants were selected and 

 inoculated with the various strains of the fungus. Inoculations wxre 



