METHODS 



197 



of the decoction was again brought up to 1000 cc), agar at the rate 

 of 1 • 2 per cent, was stirred in, and the whole boiled again for twenty 

 minutes or so until all the agar had melted. Water equivalent 

 to that lost in the second boiling was now added and then the medium 

 was filtered through cotton wool into a large beaker and cooled to 

 60° C. To clear the medium, two eggs were employed. The 

 whites were separated from the yokes, slightly beaten, set in a pan 

 with 50 cc. water, and stirred up with a spoon. The beaten whites, 



Fig. 113. — Coprinus lagojms. A haploid mycelium which has 

 been growing at the surface of dung-agar in a Petri dish for 

 48 hours. Note the wide-angled mode of brandling and the 

 presence of numerous oidial fructifications. Each of these 

 fructifications consists of an oidiophore (projecting away from 

 the substratvun into the air) crowned by a drop of fluid 

 enclosing numerous oidia. Drawn, under the direction of the 

 author, by H. J. Brodie. Magnification, 87. 



along with their crushed shells, were then added to the dung decoc- 

 tion while this was at 60° C. ; and the whole was stirred very slightly 

 to prevent the whites from completely settling at the bottom of the 

 beaker. The beaker was then set in an Arnold steriliser and steamed 

 for one hour. The clear hquid in the upper part of the beaker was 

 then poured into a filter funnel containing cotton- wool ; and, when 

 it had passed through, the rest of the contents of the beaker con- 

 taining the coagulum was also poured into the funnel through 

 which its liquid portion slowly passed. The cleared dung-agar was 

 then tubed and sterilised at 15 lb. pressure for one hour in an 

 autoclave. 



The Petri dishes used were of two sizes : ( 1 ) 10 cm. in diameter, 



