CHAPTER VII.— PHENOMENA OF VEGETATION.— GENERAL CONDITIONS. 353 
nature of their environment, while each individual according to its particular organ- 
isation has a special reaction on the influence exercised by these agencies ?. 
In judging of the phenomena which present themselves to our notice, it is at 
least as necessary to consider the influence of temperature on the vegetation and 
growth of Fungi as the temperatures of germination noticed above. In this relation 
also plants are subject to fixed rules. Every vegetative (and fructificative) process has 
certain limits of temperature and a fixed optimum in each species. In Wiesner’s 
series of experiments cited above on page 349, all other conditions being the same, the 
optimum in the growth of the mycelium of Penicillium glaucum was about 26° C., that 
in the formation of gonidia, like that of germination, was about 22°C. Many Fungi 
which are natives of our temperate zone probably exhibit the same relations to 
temperature as Penicillium. That there are differences, however, between one species 
and another is shown at once by the circumstance, that some Moulds make their 
appearance spontaneously in closed places, ceferis paribus in the hottest time of the 
year, and it may almost be said at no other time. I observed this for instance years 
ago in the case of Aspergillus clavatus, Desm. According to Siebenmann’s? statements, 
which, it is true, require further testing, Eurotium repens flourishes in a temperature of 
from 10° to15° C., and disappears at 25°C.; the same is said to be the case with E. Asper- 
gillus glaucus; A. albus and A. ochraceus do well at from 15° to 20°C., but suffer if the 
temperature rises above 25°C. In A. niger, on the contrary, Raulin® found that the 
optimum in the formation of mycelium and gonidia was ceteris paribus 34° C.; in 
A. fumigatus Lichtheim * places it at from 37° to 40°C. These statements contain limits 
which may at all events be turned to account. All but the two last are imperfect, 
because they give no exact information as to the nature of the substratum and any 
other forms which may have been growing with those observed. 
Transgression of the limits of the temperatures of vegetation leads at first in the 
Fungi, as in all plants, to rigidity whether arising from heat or cold, without destroying 
life. There are of course individual and specific differences in the power of resisting 
unfavourable influences, but it may be assumed that the higher limit of endurance in 
most Fungi in a state of vegetation, as in other plants, is about 50° C., though it is 
sometimes higher than this in a stage of rest when they contain little water, as is the 
case with spores ; on the other hand daily experience tells us, that many growing Fungi 
can stand a hard frost. The excessive power of resistance displayed by Saccharo- 
myces has been already noticed at page 347. 
The time also which is required for extreme temperatures to take effect is of 
course to be considered in all cases. 
Section XCVIII. Chemical analysis and an examination of the organisation of 
Fungi teach us that they have the same need of food as other plants, and like them 

1 On the observed effects of light on the growth of Fungi and on the phenomena of etiolation, 
geotropism, heliotropism, hydrotropism, and thermotropism see Pfeffer's Physiologie and the 
references there to other works. Also, Wortmann, in Bot. Ztg. 1881, p. 368 and 1883, p. 462, and Van 
Tieghem in Bull. Soc. Bot. de France, Febr. 11, 1876, and in Ann.d.sc nat. ser. 6, IV, p. 364, also 
in his Traité de Botanique, pp. 116, 301, and Molisch, in Bot. Ztg. 1883, p. 607. 
2 Die Fadenpilze Aspergillus, &c. u. ihre Beziehungen zur Otomycosis, Wiesbaden, 1883, p. 24. 
3 Ann. d. sc. nat. ser. 5, XI, p. 208. * As cited on page 349. 
[4] Aa 
