STUDIES OF GLOMERELLA FROM DIFFERENT HOSTS. 45 



On April 30 other plates were poured, using conidia from a leaf 

 taken from a plant in the greenhouse. Germinating conidia were 

 transferred from one of these plates to two tubes. On May 15 both 

 the tubes and the plate showed acervuli with pinkish masses of 

 conidia, and a number of areas of fertile but immature perithecia 

 were found in the plate. The conidia were much more abundant in 

 the tubes than in the plates. Later, a few fertile perithecia developed 

 in the tubes. Transfers of conidia from these tubes to flasks of corn 

 meal grew rapidly and in about a week perithecia formed, but no 

 conidia could be found. A little later the perithecia matured and 

 gave an abundance of ascospores. Plates poured, using these asco- 

 spores, produced few conidia and no distinct acervuli, but numerous 

 chlamydospores and an abundance of fertile perithecia. 



Many other transfers from this material, both of conidia and asco- 

 spores, showed considerable variation in the appearance of the growth 

 and the relative development of conidia and perithecia. Perithecia 

 usually predominated in the plates, whether started from conidia or 

 ascospores. Conidia were more frequently scattered and hyphomyce- 

 tous than in distinct acervuli. Various attempts were made to deter- 

 mine whether the amount of culture medium used in the plates or 

 the thinness and thickness of the sowing of the spores had any direct 

 relation to the production of ascospores or perithecia. In the case 

 of a strain of the fungus which normally produced perithecia it 

 appeared that perithecia were more numerous and conidia less so 

 in plates which were thickly sown. In about a dozen cases peri- 

 thecia were found forming along the sides of cotton fibers winch 

 happened to be present in the agar. This suggested that the resist- 

 ance of some solid substance might possibly stimulate their formation. 

 In many cases, especially in this form from Persea, the perithecia 

 showed a tendency to develop about an acervulus, forming a small 

 cluster or group, with the acervulus as a stromatic base. 



Two series of generations of pure-line cultures were started from the 

 same original culture of this organism. In one case ascospores only 

 were used and in the other case conidia only. The ascospore cultures 

 were carried through seven generations on the same medium and under 

 practically the same conditions of growth and environment. The 

 conidial cultures were carried through 23 generations and their 

 behavior was compared with the generations from ascospores, as well 

 as with duplicate cultures of each generation. An account of these 

 cultures will be given later under the head of " Pedigreed cultures." 



The conidia from leaves in moist chamber varied from 11 to 19.5 

 by 4.5 to 5.5 /*. Conidia from cultures varied from 12 to 18 by 4.5 

 to 6 /£. Ascospores from leaves averaged about 18 by 6 /*. Those 

 in cultures ranged from 13.5 to 22.5 by 4.5 to 6 ji. An ascus and 

 ascospores are shown in Plate I, figures 10 and 10a. Bessey (12) 



252 



