559 
Balls . — Temperature and Growth. 
straight 1 . When the surface of the liquid has been covered with mycelium, 
the hyphae grow up the sides of the flask and may even fill the interior with 
‘ flying hyphae \ Resting cells are formed in abundance. 
Cultures stored at 34° C. developed mycelium which had a fluffy 
appearance owing to the development of numerous short aerial hyphae, 
which were extensively branched and feathery. The long flying hyphae 
are not developed, resting cells are but sparsely formed, and growth ceases 
much sooner than in the cool cultures. This cessation of growth is 
commonly known to mycologists as c staleness \ 
In one experiment where the volume of the medium was about 100 cc. 
growth continued steadily for four days at 33° C., but on the fifth day the 
edge of the disk had ceased to grow. When these stale flasks were diluted 
with sterile water and re-inoculated the fungus grew freely again, although 
undiluted controls remained as incapable of supporting growth as before. 
The time required for the completion of 4 staling * is less at high 
temperatures than at low ones, and it is also affected by the volume of the 
medium. 
Mode of growth. The growth of this fungus is seen to be entirely 
apical, and never intercalary, when examined under the microscope. 
A slight contraction may be noted in cooling a culture, but this is probably 
due to a change in the permeability of the protoplasm. 
Hyphae taken from a cool culture show vacuoles, but these disappear 
on heating, and when a hypha is growing at high temperatures it appears 
to be homogeneous. The increment in length measured under the micro- 
scope thus represents fairly the actual increment in bulk of the protoplasm. 
Possibly the absence of vacuoles may facilitate the staling process. 
The apical zone of growth is very small ; the hyphae are not more than 
10 microns in diameter, and the longitudinal extension of the zone is not 
more than 5 microns. Growth can be measured with considerable accuracy 
by taking some mark, bend, or side branch near the apex as a control 
point 
The hyphae branch fairly freely and all branches of a hypha — which 
implies all the hyphae in a culture — show the same temperature relation- 
ship, as can be seen when readings are obtained simultaneously from two 
or more adjacent hyphae. 
Chemical Composition of a Stale Culture. The substances which cause 
staling have not yet been chemically identified, but it has been proved that 
a culture does not become stale of necessity because its food supply has been 
exhausted. 
For this purpose the Urea Medium was employed 2 ; when all growth 
had ceased the flasks were re-inoculated for extra assurance of their 
inability to support growth, and the medium was then analysed quali- 
1 Khed. Agric. Soc. Year Boole, 1905. 2 Page 565. 
