16 BULLETIN 395, U. S. DEPAKTMEIsfT OP AGEICULTUEE. 



showed only minor variations upon the different substrata. The 

 more important features of this work are outhned as follows: 



Lvma-hean agar plates. — In diffuse light in the laboratory, at 18° to 25° C, the 

 conidium puts out one or more colorless septate germ tubes, each of which in two days 

 may attain a length of about eight to twelve times that of the spore. The cells of these 

 hyphse then thicken, develop numerous lateral branches, and become olivaceous. 

 The younger hyphae behave in hke fashion. Thus small, compact colonies develop, 

 their central areas being composed of dense, pseudoparenchymatous masses of heavy, 

 often swollen and moniliform, thick-walled, olivaceous cells from which radiate 

 numerous branched hyphse. The colonies usually become macroscopic within three 

 to five days and attain their full development within two to four weeks. When fully 

 developed they may be irregularly spherical to lens shaped or irregular and more or 

 less submerged, depending upon the position of the parent spore. The exposed por- 

 tion of the stromateoid mass is masked by an olive-green covering of conidiophores, 

 conidia, and rather sparse, slender, olivaceous, aerial hyphse. The submerged parts 

 are dense and black, except at the periphery, where the young hyphse are colorless. 

 While the size of the colonies varies much with conditions, the surface diameter 

 averages about 1 to 4 mm. 



Lima-beani agar slants. — ^The early development of the fungus parallels that on 

 plates. The subsequent growth, however, is much more vigorous and continues for 

 a longer period. In a culture seeded with a small droplet of sporiferous suspension 

 on the middle of the slanted surface and incubated at 18° to 25° C. under conditions 

 which retard rapid evaporation, the colony may eventually occupy practically the entire 

 slant, gradual growth continuing for more than three months. At the end of four 

 months the exposed portion consists of a black, irregularly circular, stromateoid mass 

 about 1 to IJ cm. in diameter, somewhat raised and slightly convoluted, masked by 

 an olivaceous covering of conidiophores, conidia, and slender, aerial hyphse. From 

 thiR central mass heavy, branched, olivaceous to black hyphse penetrate the slant 

 practically to the wall of the tube. 



Beerwort agar slants. — The early development closely parallels that on the Lima- 

 bean agar, except that it is somewhat more rapid and the growth above the surface of 

 the medium is markedly more abundant. The latter difference becomes very striking 

 in later stages, when the much-folded and convoluted mycelial masses of the cultures 

 on beerwort agar extend several millimeters above the original surfaces of the slants, 

 sometimes reaching the opposite walls of the tubes. The subsurface development 

 extends through the slants to the walls of the tubes. In the later stages the raised, 

 stromateoid masses become studded with microsclerotia. 



Other agar slants. — Strains of the fungus isolated from (a) fruit, (b) twig, and (c) leaf 

 lesions were studied comparatively on 16 agar preparations, viz, infusions of peach 

 fruit, peach leaf, peach twig, prune (pitted, 2 per cent and 5 per cent), Lima bean, 

 potato, corn meal, oat meal, and string bean; standard beerwort, malt soup, synthetic, 

 Thaxter's potato hard (3 per cent agar), beef-extract agar; and agar alone (1.5 per 

 cent) in water. These media were prepared with the aim of securing as much uniform- 

 ity as feasible in matters common to all, as periods of cooking and sterilization, per- 

 centage of agar used (1.5 per cent, unless otherwise noted), and technique of manipu- 

 lations. For the standard media standard methods were followed throughout. All 

 the media were titrated,, but it was not considered desirable to readjust the reactions, 

 previous tests having shown no noticeable effect ol reaction in a range more extensive 

 than that occurring in these cultures. The cultiues were made in triplicate, incu- 

 bated in darkness at 20° to 22° C, and examined frequently during their development. 



While the development of the fungus varied considerably with the different media, 

 these variations did not appear to be of a nature to justify detailed descriptions. The 

 chief differences were (1) the amount of growth above the siu-face of the slant, (2) the 



