I2 6 RESEARCHES ON FUNGI 



Rate of Growth of the Mycelium in a Dung-agar Plate.— On a 

 plate of cleared dung-agar at about 20° C, the mycelium of Pyronema 

 confluens grew radially at the rate of 5-4 cm. (approximately 2-1 

 inches) per day of 24 hours. This is an extraordinarily rapid rate 

 of growth which, combined with quick germination of the spores x 

 and early fruiting, 2 doubtless helps to explain why it is that the 

 fungus spreads so rapidly, and at first often dominates other fungi, 

 on burnt ground, sterilised soil, etc. There is every reason to 

 believe that the rapid growth of the mycelium is aided by the free 

 flow of the protoplasm from cell to cell toward the ends of the 

 growing hyphae. It was found that in plate cultures the leading 

 radial hyphae, on reaching the edge of the dung-agar, grew up the 

 glass sides of the dish and on to the glass cover for a distance of 

 about 2 cm. before their further development was checked. This 

 advance over the surface of non -nutrient glass must have been at 

 the expense of a supply of nutriment sent from the hyphae in the 

 dung-agar, and in all probability protoplasmic streaming played a 

 chief part in the translocation process. 



Observations with Dark-field Illumination. — With the help of 

 Dr. P. H. Gregory, I made a few observations on the mycelium of 

 Pyronema confluens with a Leitz dark-field condenser. A hanging 

 drop of Sabouraud's medium, as used for cultivating ring- worm 

 fungi and other dermatophytes, was inoculated with mycelium, and 

 the next day the mycelium had spread in the drop. The cover- 

 glass with the hanging drop was now removed from the van-Tieghem 

 cell and set on a drop of water on a glass slide, and the mycelium 

 was examined under the microscope with the aid of the dark-field 

 condenser. The objective was a one-twelfth inch oil immersion, 

 fitted with a diaphragm, and the ocular was 10 X . The magnification 

 was about 1,000. 



The hyphae stood out as bright objects against a black back- 

 ground. The vacuoles were clear black, but the massive granular 

 protoplasm in the interior of the cells everywhere glittered and 



1 Vide supra, p. 113. 



2 According to Robinson (loc. cit., p. 247) " a culture from a single spore carries 

 through its developmental cycle to the ascus and mature ascospore on a suitable 

 medium, if illuminated at a favourable temperature, in from eight to fourteen days." 



