1893.] MICROSCOPICAL JOURNAL. 123 



tliL- third dilution. Experience ciuibles one to jud^e ijuite accu- 

 rately in niakinii^ the dilutions so that we estimate the dilution 

 sulHcient to cause each <;erin to lie separately at dilVerent points 

 in the lic|iiid ai^ar. at least in dilution No. 3. 



Each of these dilutions was then poured into a petric dish,* 

 and allowed to cool in a thin layer over the bottom. No germs 

 could then be seen in the agar, since they are microscopic and 

 lie singly. The dishes were jiiled away lor a few days. During 

 this time each germ grew and produced a colony which was visi- 

 ble to the unaided e\e. 'J'he ])hites or dish cultures were now 

 photographed naturalsize and the result is produced in the frontis- 

 piece. In Xo. 3 it will be seen that nearly all of the coh^nies are 

 separate. The snowflake-like colonies are those of the desired 

 fungus. The small, compact, circular ones are those of bacteria. 

 One large compact colony is that of a common fungus. 



In Nos 2 antl i the fungus colonies are crowded, and have not 

 made such good growth. I he colonies of bacteria are more 

 numerous also, and it would be very difficult to olitain a pure cul- 

 ture of the fungus in either of those dilutions. If the dilutions 

 were not numbered it vvoultl be an easy thing to determine their 

 nuinl)er from the size and number of the colonies. The very 

 large compact colony in No. 2 is that of a motile bacterium. 



Pure Cultures of the Anthracnose. — Pure cultures of the 

 fungus could now be started l)y transplanting with a flamed plati- 

 num needle portions of the fungus colonies from No. 3 into a cul- 

 ture-tube of nutrient agar. The photograph was taken after these 

 transplantings were made, which accounts tor the broken appear- 

 ance of some of the colonies. 



From the point of inoculation in the cultme-tube, where the 

 transplanting was made, the fungus threads grow out through the 

 upper surface of the agar, radiating in all directions. In a few 

 days minute black bodies appear seated here and there upon the 

 mycelium. These resemble the stroma at the base of the pus- 

 tules on the stem, but in the artificial cultures do not seem to be 

 especially concerned in the production or basidia and spores, 

 since but a few are developed in connection with them. 



Numerous basidia and spores are produced, however, all along 

 the threads, and a mass of them at the point of inoculation. In 

 a few tlavs more many fungus threads arise above the agar and 

 produce a fluHy white growth upon the surface, nearly obscuring 

 the black points. 



No pigment was noticeable in these cultures. New cultures 

 were then started by transplanting portions of agar the size of a 

 small pea with a mat of mycelium and spores to fresh culture- 

 tubes. In the fresh agar the growth took place in the same man- 

 ner as in the first tubes, but upon the surface of the transplanted 

 portions a faint pink pigment appeared. 



* A pctrie di^ft is composed of two shallow glass vessels, one about three inches in diame- 

 ter, which serves as the bottom ; the other ofa little greater diameter, which is inverted over the 

 first one for a cover. 



