42 2 Bulletin 315 



that the results of some workers can be attributed to cultures which are 

 not the descendants from a single spore. The acute observer, and he who 

 has worked with the Mucors to any extent, knows that it is no easy task 

 to pour plates with spores distributed singly. Usually they adhere in 

 twos and threes. Hagem is the first to warn us in print of this condition. 

 His method of obtaining pure cultures from a single spore is based pri- 

 marily on this fact and is as follows : 



With a platinum needle, some spore material is transferred to a flask containing 

 about 30 cc. of sterile water. After vigorous shaking, one pours a few cuImc centimeters 

 of the spore-containing water into a second flask containing water, and again after 

 vigorous shaking a few drops are transferred from the second flask to a third. After 

 repeated shaking of this, 2 cc. are poured on the solid nutrient stratum of a poured petri 

 dish and distributed over the whole surface. The spores are now allowed to settle and 

 thereafter the water is carefully poured from the dish. The dish is now left at room 

 temperature for two to five days, and when the spores have begun to germinate an 

 attempt is made to isolate a colony. To do this, the dish is opened and brought quickly 

 under the microscope (enlargement about 50). At a glance one. detects whether the 

 colony has originated from a single spore. Transfer is now made to the substratum 

 of a second dish. 



This operation of determining that a colony is the product of a single 

 spore allows some possibility of contamination while the plate is left 

 uncovered and during the observation. The chances of contamination 

 are very slight, however. 



The writer employs a method in vogue in the laboratory of the Department 

 of Plant Patholog3% Cornell University, which is probably somewhat 

 more commendable than that of Hagem. This method can be used to 

 advantage especially when pouring plates with spores as large as those of 

 most species of Mucor. The method is as follows: Plates are poured so 

 that a very thin layer of the solid nutrient medium covers the bottom of the 

 dish. Inoculation of the plates is made after the Hagem method. After 

 germination of the spores, instead of removing the cover of the dish, the 

 dish is inverted and placed on the stage to make the observation. 

 The glass immediately above the spore (this, of course, while the dish is 

 inverted) is marked with india ink in order to asstire no mistake in transfer 

 of the proper colony. 



Contemporary with Hagem in Norway, we find Lendner ('08) in Switzer- 

 land at work on a study of the Mucorales as to distribution, culture, 

 classification, and so on. His studies have resulted in the admirable 

 monograph already cited. In a study of the habitat of the species of this 

 order, the author considers, in connection with a number of pabula, that 

 of the soil. One species, Mucor hotryoides, is not listed in the monograph 

 but has been isolated from the soil more recently by Lendner ('10). 



('08) Lendner, Alfred. Les Mucorin6es de la Suisse. 1-180. pis. 1-3. fig-SQ. 1908. 



('10) Nouvelles Contributions a la Flore Cryptogamique Suisse. Bui. 



Soc. Bot. Geneve ser. 2, 2: 78-81. figs. 1-4. 1910. 



