216 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Bainier ('82, '83'', '84, '89, '03) has been especially successful in 

 obtainiug zygcrspores, but though he concludes that the substratum has 

 much to do with their production, he is at variance with previous authors 

 in that he says ('SSb. p. 344) " when the plant finds the nutriment inferior 

 it produces sporangia ; when the food supply is abundant, zygospores 

 appear." He looks upon the zygospores as so much stored-up nutriment, 

 and consequently implying a very vigorous condition in the plant produc- 

 ing them, and demanding that the thallus be able to extend itself in length 

 and depth. His point of view, with the theory resulting from it, is thus 

 radically different from that, of van Tieghem, who looked more on the 

 function than on the formation of this condensed mass of nourishment, 

 and consequently considered Chat the formation of a resting spore must be 

 brought about by the apjoearance of those unfavorable conditions against 

 which it was designed to protect the plant. As regards moisture, Bainier 

 thinks there can be nothing said in general, the species differing in their 

 preference for more or less dryness. The season of the year and the 

 temperature seem to be with him factors of some importance, for in his 

 notes on the zygospores of different species the months in which they are 

 supposed to form is generally stated, and in his latest work ('03), where 

 zygospores are described for a considerable number of species, the special 

 condition mentioned is the low temperature of a cellar where his cultures 

 were kept during a warm period of summer. A majority of Bainier's 

 zygospores were obtained in van Tieghem cell cultures in a concentrated 

 decoction of plum and prune, which was sterilized by boiling and mixed 

 with ten to twenty per cent of alcohol to prevent fermentation. This 

 investigator further states that freedom from parasites is a condition to 

 be satisfied before zygospores can be expected, in marked contrast to the 

 opinion expressed by Zopf ('88 and '92) in connection with his study of 

 Pilobolus, where the suppression of sporangia through the attacks of a 

 parasite is regarded as responsible for the appearance of zygospores 

 (cf. p. 238 of present paper). 



Brefeld's ('75, '81, '00) position has been one of agnosticism as regards 

 the causes for the appearance of zygospores, and the valuable part of 

 his conclusions is contained in a series of denials substantiated by the 

 results of his cultures. The character of the nutriment alone he holds 

 to be of slight significance, since on the same substratum from differently 

 derived spores of the same fungus, e. g. Piptocephalis, he obtained on 

 the one hand zygospores, and on the other only nonsexual sj)ores. 

 Changing the substratum and the oxygen content of the air did not alter 

 the results. The age of the mycelium is likewise not considered influen- 



