THE PRODUCTION OF THE ASCOGENOUS FORM. 19 



appendage is borne. The mycelium now grows more rapidly and soon 

 assumes the color and other characteristics mentioned in the descrip- 

 tion of the macroscopic appearance of cultures of the fungus. 



The appendage of the pycnospore, as seen upon immature spores, 

 consists of a hazy, hyaline, finely granular, gelatinous mass, equaling 

 the spore in diameter (PI. II, fig. 3). A little later it becomes some- 

 what elongated, curved backward, and more or less appressed on the 

 side of the spore. As the spore matures the appendage becomes still 

 narrower and free from the side of the spore, but even at maturity it 

 is usually somewhat curved. In old cultures which have passed 

 maturity and in which all the spores have been set free, the append- 

 age is frequently wanting and seems to have been dissolved or 

 disintegrated. 



No signs of a conidial form of the fungus have been found in any 

 of the numerous cultures made, either from the mycelium or spores. 

 No chlamydospores have been found in cultures, but what appear to 

 be such are found in old berries destroyed by the fungus. Sterile 

 pycnidia or perithecia are frequently found, especially in poorly 

 developed cultures. These are sometimes solid and sclerotoid, with 

 the interior cells lighter colored, and are about the same size as the 

 pycnidia and perithecia. 



CONDITIONS OR FACTORS DETERMINING THE PRODUCTION OF THE 

 ASCOGENOUS FORM. 



The reasons for the rare occurrence of ascus-bearing forms in cul- 

 tures of what are undoubtedly ascomycetous fungi have always been 

 obscure, and it has usually been found impossible to produce the 

 ascogenous fructifications with much frequency or certainty. 



The w^ork of Jlebs 19 and others upon the effect of various nutrient 

 and other substances upon the production of sexual fructification, 

 especially in the alga?, has suggested the possibility of such factors 

 having a determining influence on the production of the ascogenous 

 stage in this fungus. While our experiments in this direction have 

 been comparatively few, there has been no indication that the compo- 

 sition of the culture medium is of particular importance in this 

 respect. When once an ascus-producing race, strain, or generation 

 of the fungus was obtained it grew almost equally well upon different 

 culture media, such as steamed corn meal, cranberry gelatin and corn 

 meal, cranberry agar and corn meal, and potatoes. 



The effect of variations in temperature has also been tried upon 

 a series of pycnospore-producing cultures made from the same 

 original pure culture. Cultures in flasks on corn meal were kept 

 in the laboratory, where the temperature varied from 20 to 26 C. 

 Others were kept in a thermostat at- a temperature of 30 C. Others 

 110 



