240 PEOCEEDINGS OF THE A3IERICAN ACADEMY. 



Pilobolus nanus van Tieghem. 



The thick-walled tuberculate "spores durables" which van Tieghem 

 ('76, p. 341, Plate X, Figure 22) describes as developing terminally ou 

 short curved stalks from the mycelium, are considered by Fischer 

 ('92, p. 268) to be azygospores. 



Mortierella Rostaflnskii Brefekl. 



According to Brefeld ('81) cultures of this species may be run through 

 a continuous series, perhaps to ten or twelve generations, with exclusively 

 non-sexual reproduction, when zj'gospores largely take the place of 

 sporangia. In further cultures made with the mycelium or with spo- 

 rangial spores, he obtained zygospores continuously and in great abun- 

 dance. There is nothing said which would indicate whether these 

 sporangial transfers were made from a single sporangium or from several, 

 in which latter case sexual strains, if such existed, might have been mixed. 

 From the intricate network of hyphae that surrounds the young zygo- 

 spore, it was not possible to determine whether the conjugating branches 

 were formed from the same or from two different stolons. The fact that 

 zygospores would not form on slide cultures while they were found on 

 the free walls of his culture dishes is highly suggestive of a heterothallic 

 condition when we remember that it was Brefeld's practice (I.e., p. 11 

 and 12) in making slide cultures, to use spores from a single sporangium. 

 The zygospores themselves, when placed in a moist atmosphere, did not 

 germinate, but the enveloping hyphae gave rise to sporangia or to new 

 zygospores. The latter condition is not inconsistent with a supposition 

 that the enveloping as well as the conjugating hyphae are from different 

 mycelia. 



Mortierella nigrescens van Tieghem. 



Van Tieghem ('76) found this species several times in October, 1875, 

 on different agarics, boleti, and ou Lycoperdon, and cultivated it on 

 Agaricus campestris and truffles. In June, 187C, the fungus was again 

 found and cultivated on Agaricus campestris where the zygospores were 

 obtained. " The small tubercle composed at maturity of an envelope of 

 many thicknesses of crowded branches enclosing the zygospore is inserted 

 by a short pedicel upon a filament of the mycelium and sometimes at the 

 point of anastomosis of several different filaments." The morphological 

 observations and figures apparently indicate that the progametes arise in 

 a tuft from a single hypha. It seems strange that if this is a homotliallic 

 species, van Tieghem should have been unable to get the zygospores 



