BLAKESLEE. — SEXUAL REPRODUCTION IN THE MUCORINEAE. 249 



During this period of investigation, ouly a few series of comparative 

 cultures were carried on, since it became evident at the very outset, as 

 was shown by the experiments already mentioned, that the influence of 

 external conditions was a wholly inadec^uate explanation of the presence 

 or absence of zygospore formation in this species. Such tests as were 

 then made are summarized in the following table. The natural sub- 

 stances mentioned were sterilized iu the autoclave at about 125° C, and, 

 after inoculation with a few drops of sterlized water which contained a 

 mixture of spores from a zygosporic culture, were kept covered in a 

 drawer in the laboratory, with the results indicated in Table I. 



In the following stender dish cultures shown in Table II, pieces of 

 sponge and masses of sphagnum were cleansed, sterilized, and soaked 

 with the different liquids tested, the inoculations being made from a 

 mixture in sterilized water of spores from a zygosporic culture. It will 

 be seen that the formation of zygospores occurs when such dilute nutri- 

 ents are used as are available either iu a one per cent solution of grape 

 sugar on sponge, or in damp sterilized Sphagnum. On sponge, peptone 

 alone in varying per cents is unable to support the formation of zygo- 

 spores. Perhaps owing to the dilute solutions used, the sponge cultures 

 did not produce a luxuriant vegetation. In general, however, it is 

 noticeable that the carbohydrate, grape sugar, in contrast with the same 

 per cents of the nitrogen compound, peptone, affords a nutrient compara- 

 tively favorable to the production of zygospores. 



TABLE II. 



Substratum. Results. 



Sponge with distilled water no growth. 



" " dilute prune decoction sporangia ; few z3'gospore3. 

 Sphagnum with distilled water sporangia ; few zygospores. 

 " " dilute prune decoc- 

 tion sporangia; zygospores somewhat abundant. 

 Sponge with 0.5% grape sugar few sporangia; no zygospores. 



" " 1.0% " " sporangia; very few zygospores in cavities 



of sponge. 



" " 2.0% " " sporangia ; no zygospores. 



" " 5.0% " " sporangia ; few zygospores. 



" " 7.0% " " sporangia few ; no zygospores. 



" " 10% " " sporangia ; few zygospores. 



" " 0.5% Peptone sporangia scanty ; no zygospores. 



" " 1.0% " sporangia scanty ; no zygospores. 



" " 4.0% " sporangia scanty ; no zygospores. 



In Table III nutrients in stender dishes were sterilized as before in 

 the autoclave and inoculated with a mixture in sterilized water of spores 



