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 l . 



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 2 2 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, ceteris 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 2 statements, 

 which, it is true, require further testing, Eurotium repens flourishes in a temperature of 

 from 10 to 15 C., and disappears at 25C.; 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 3 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 Physiologic and the 

 references there to other works. Also, Wortmann, in Bot. Ztg. i88i,p. 368 and 1883, p. 462, and Van 

 Tieghem in Bull. Soc. Bot. de France, Febr. n, 1876, and in Ann.d.sc nat. ser. 6, IV, p. 364, also 

 in his Traite de Botanique, pp. 116, 301, and Molisch, in Bot. Ztg. 1883, p. 607. 



2 Die Fadenpike 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. 



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