300 PROCEEDINGS OF THE AMERICAN ACADEMY. 



wet filter paper covering the culture. The maximum and minimum 

 temperature limits have not been determined for the grovpth of the 

 species, yet it is certain that both sporangia and zygospores are produced 

 up to 29° C. 



It may be seen from the foregoing cultural experiments that the 

 formation of zygospores is practically independent of the external con- 

 ditions to which the growth of the fungus is subjected. 



DlCRANOPHORA SP. 



This homothallic form, an undescribed species of the genus Dicrano- 

 phora, has been given the writer by Professor Thaxter, who found it 

 growing on Boleti at Kittery Point, Maine. 



Few cultural experiments have been tried with the form, but such as 

 have been made indicate that external conditions are more influential in 

 determining the form of fructification than was the case in Mucor i and 

 II and in Zygorhynchus. On the ordinary nutrient agar used in its 

 cultivation, zygospores form abundantly on the substratum, and even in 

 its interior, when soft agar is used. Upon tap water with pure agar 

 growth is slow, and after several weeks the culture shows only a meagre 

 production of sporangia without zygospores. Although when grown 

 under favorable conditions of cultivation, sporangia and zygospores are 

 formed simultaneously from the same mycelium, yet it is possible, by a 

 decrease in the relative humidity of the surrounding air, to decrease the 

 formation of zygospores and increase that of sporangia. Thus of three 

 stender dish cultures on nutrient agar in which the mycelium had just 

 become visible, the one left covered in a culture drawer produced abun- 

 dant zygospores and comparatively few sporangia ; while the other two, 

 one of which was placed uncovered on a laboratory table, and the other 

 in a sealed vessel with calcium chloride, where the surrounding air was 

 comparatively dry, produced sporangiophores but no zygospores. 



From the abundantly branched mycelium are developed numerous 

 stubby, much-lobed branchlets the majority of which remain sterile. 

 On account of the difficulty of distinguishing the sterile outgrowths from 

 the parts destined to produce zygospores, and on account of the fact that 

 the smaller zygophoric branch is usually beneath and concealed by the 

 larger, it is a matter of some difficulty to obtain the early stages of 

 conjugation. Enough has been seen, it is believed, to determine the 

 main points of the process. The form is distinctly heterogamic, and a 

 difference is from the very start apparent between the two zygophoric hy- 



