BLAKESLEE. — SEXUAL RErRODUCTION IN THE MUCORINEAE. 293 



sealed vessel with calcium chloride suffered but little more desiccation 

 thau those exposed on the laboratory table. 



From the fact that zygospores are readily produced on plain bread 

 and from the observed effects of relative humidity on the type of fructi- 

 fication produced, the material investigated agrees with that used by 

 Klebs, and the results obtained seem to give sujDport to the suggestion 

 that Falck worked with a form at least physiologically somewhat different, 

 if not unusual. 



Spinellus fusigeu. 



Next to Sporodinia, this species seems to have been more frequently 

 found than any other homothallic form. It has not been cultivated by 

 the writer, but he has been enabled to examine dried material from a 

 number of different stations, as has been mentioned under this species in 

 the Citations in Part I. The zygospores in all cases were found to 

 be abundant between the gills of the host, and the connections of their 

 suspensors could frequently be traced to the same branch of the spiny 

 mycelium. 



Its homothallic character is thus determined beyond question. 



MUCORS I AND II. 



This section will treat of a homothallic species or of a group of per- 

 haps three forms which are very closely related. In October, 1901, the 

 writer made a pure transfer from a Mucor growing apparently unaccom- 

 panied by zygospores on a culture of a decaying agaric and obtained 

 the homothallic species which has been called in the present paper 

 JNIucor I. Mucor ii was found by Professor Thaxter, January, 1898, at 

 Daytoua, Florida, growing spontaneously with its zj-gospores on a de- 

 caying Polyporus. A third form was obtained from a separation culture 

 made in June, 1901, by Mr. E. E. Bogue from the " schleimflUss " on a 

 recently cut birch stump. The mycelium was mixed on the soft agar 

 with bacteria and yeasts, and produced on aerial hypliae only zygospores 

 which were at first mistaken for sporangia. By making a number of 

 mycelial transfers a pure culture was secured which produced sporangia 

 as well as zygospores, and since this time no cultures have been obtained 

 which would yield zygospores exclusively. In most cultures of this, 

 as of the other two forms, zygospores and sporangia are generally both 

 present in abundance. 



It is possible that the form just mentioned is identical with one or the 

 other of the first two forms. The three if not identical are sufficiently 



