122 



SCIENCE. 



[N. S. Vol. XXIV. No. 604, 



method of obtaining the zygospores of Cun- 

 ninghamella by contrasting in cultures dif- 

 ferent strains of this species. By a sufficient 

 accumulation of material from different 

 sources, one might expect eventually to ob- 

 tain the two sexual strains and, by their syn- 

 thesis, the zygospores as well of any form in 

 which the sexes are separated on different 

 mycelia. 



Undoubtedly a careful search below the 

 sporangial growth would show that zygospores 

 are more common in spontaneous cultures 

 than is usually supposed. In searching for 

 forms of the mucors, the writer had occasion 

 to make cultures on sterilized paste and on 

 bread of various substances among which the 

 shells of different kinds of nuts were thus 

 investigated. It may not have been a mere 

 accident that in all the several instances in 

 which shells of almond nuts were used, zygo- 

 spores were produced, but failed to appear 

 when shells from other kinds of nuts were 

 employed. These almond nuts were obtained 

 from different places in the neighborhood of 

 Boston, though they all probably came from 

 the same source originally. The writer would 

 be glad to learn if others have a similar ex- 

 perience with the shells of this species from 

 other localities. 



In making cultures, the bread should be 

 raised above the bottom of the culture dish 

 by some convenient object, otherwise the bread 

 is likely to become soggy and attacked by bac- 

 teria. Layers of moistened iilter paper on the 

 sides and bottom of the dish, which should be 

 covered, ensure a proper moist condition in 

 the surrounding air. Those desiring to have 

 absolutely pure cultures may first sterilize the 

 bread dry and then allow it to soak up a suffi- 

 cient amount of sterilized water to give it a 

 spongy consistency, after which it may be 

 sterilized with steam for about five minutes. 

 Prolonged sterilization as well as too much 

 water in the bread makes it soggy and less ad- 

 vantageous for cultures. Sterilization is not 

 necessary, however, for class work. Zygo- 

 spores when present are likely to form in 

 dense masses between the layers of moist filter 

 paper lining the culture dish or in the folds 



of crumpled pieces of filter paper placed in the 

 culture as traps for their capture! Sporangia 

 form where the air is dryer, and the habit of 

 growth can be readily studied from the filter 

 paper in the upper parts of the culture. The 

 individual stolons can be more easily distin- 

 guished if darkened paper be employed. When 

 zygospores are once obtained, mass transfers 

 of the mycelium may be made to new cultures 

 and thus the Penicillium, which is a usual 

 weed in spontaneous cultures, may be elimi- 

 nated. A culture producing zygospores may 

 be dried with its substratum and used from 

 time to time as ' seed ' whenever zygospores 

 are needed. Zygosporic cultures of the ' Har- 

 vard Strain ' have thus been kept running 

 for nearly ten years. The sporangiospores of 

 Bliizopus are comparatively short lived, how- 

 ever, and generally do not retain their vitality 

 for more than a year. 



Eor methods of separating out the two sex- 

 ual strains from a zygosporic culture, which 

 is often a tedious process, one may refer to 

 the writer's detailed experiments with this 

 species already cited. 



A. F. Blakeslee. 



Halle, Germany. 



RESULTS FROM MOORE's METHOD OF SHIPPING 

 BACTERIA ON COTTON. 



In Science of March 23, Messrs. Kellerman 

 and Beckwith have called attention to the state- 

 ment in Bulletin 270 of the New York Agri- 

 cultural Experiment Station that [certain ^] 

 ' cultures of nodule-forming bacteria dried 

 upon cotton were worthless for practical pur- 

 poses and that the failure of such cultures was 

 inherent in the method of their preparation.' 

 At the same time they presented some excel- 

 lent data upon the effect of drying legume 

 bacteria under various conditions. Their 

 most interesting experiment consisted in pla- 

 cing a culture " on cotton half of which was 

 placed in a sterile Petri dish, to make drying 

 very slow, half was dried rapidly and kept 



^ An important word omitted by Messrs. Keller- 

 man and Beckwith in summarizing the statements 

 contained in Bulletin 270. 



