8o INFLUENCE OF THE EXTERNAL CONDITIONS ON GROWTH 



12 C., but in darkness at 15 C. Heald 1 found that the spores of ferns will 

 germinate in darkness at 32 C., although at ordinary temperatures they only 

 germinate in light. The character and quantity of food supplied is also of 

 importance. Thus Thiele 2 found that 31 C. was the maximal temperature for 

 the growth of Penicillium glaucum on sugar solution, but 35 to 36 C. when fed 

 with formic acid or glycerine, whereas in the case of Aspergillus the highest 

 maximum is reached on the most favourable nutrient material (sugar). Further, 

 according to Rabinowitsch 3 , the minimum for facultatively anaerobic thermophile 

 bacteria sinks to from 34 to 44 C. in the absence of oxygen, but rises to 

 50 C. in its presence. 



Gradual accommodation may also cause a certain displacement of the 

 cardinal points. Thus Dieudonne 4 was able to reduce the minimum for Bacillus 

 anthracis from 12 or 14 C. to 10 C. Similarly, by gradually increasing the 

 temperature of successive cultures, the same author raised the maximum of 

 Bacillus fluorescens from 35 to 41-5 C., and that of the bacillus of red milk 

 from 37 to 41-5 C., while Tsilinsky 5 succeeded in raising the maximum for 

 Bacillus subtilis from 50 to 58 C. in the course of thirty generations. The 

 previous cultural conditions seem also to exercise some influence upon the 

 cardinal temperatures for flowering plants. Thus the minimum for germination 

 varies slightly in the case of seeds obtained from similar plants growing under 

 different conditions 6 , and the period of development is shortened when the 

 seeds of cereals grown in the North are planted in more Southern regions 7 . 



The dissimilar cardinal points for different forms of growth. The minimal 

 and maximal temperatures for growth seem to be further apart for vegetative 

 growth than for the production of reproductive organs. 



Limits for vegetation. For production of reproductive organs. 

 Vaucheria repens* o to 30 C. 3 to 26 C. (zoospores). 



Anixiopsis stercorarius* 3 to 37 C. 8 to 34 C. (perithecia). 



Saccharomyces cerevisiae o to 40 C. n to 37 C. (spores). 



1 Heald, Gametophytic Regeneration, Leipziger Dissertation, 1897, p. 62. 



2 Thiele, Temperaturgrenzen d. Schimmelpilze, Leipziger Dissertation, 1896, p. 36. Some 

 forms of Penicillium glaucum seem to have a high maximum. On bacteria cf. Nageli, Theorie 

 d. Gahrung, 1879, P- 9 1 - 



3 Rabinowitsch, Zeitschr. f. Hygiene u. Infection, 1895, Bd. xx, p. 159. 



* Dieudonne, Centralbl. f. Bact., 1894, Bd. xvi, p. 965; Biol. Centralbl., 1895, Bd. XV, p. 109; 

 Fltigge, Mikroorganismen, 1896, 3. AufL, Bd. I, p. 483. 



8 Tsilinsky, Ann. d. 1'Institut Pasteur, 1899, T. xiil, p. 793. 



6 Tietz, Ueber die Keimung einiger Coniferen u. Laubhb'lzer, 1874, p. 29 ; Haberlandt, 

 Schutzeinricht. d. Keimpflanze, 1877, p. 38; N. J. C. Miiller, Bot. Unters., 1879, Bd. II, p. I. 



7 Schlfebeler, Bot. Centralbl., 1886, Bd. xxvill, p. 205. 



8 Klebs, Bedingungen d. Fortpflanzung, 1896, p. 40. On Saprolegnia see id., Jahrb. f. wiss. 

 Bot., 1899, Bd. xxxill, p. 552. On fungi in general cf. id., Jahrb. f. wiss. Bot., 1900. 



9 Hansen, Bot. Ztg., 1897, p. 129, and Klebs, 1. c., 1896, p. 488 ; 1. c., 1900; Bachmann, Bot. 

 Ztg., 1895, p. 130; F. Grantz, Einfluss d. Lichtes auf die Entwickelung einiger Pilze, Leipzig, 

 1898, p. 53. 



10 Hansen, Meddelelser fra Carlsberg Laboratoriet, 1888, Bd. u, p. 32 of abstract. For 

 a general summary see Jb'rgensen, Mikroorganismen d. Gahrungsindustrie, 1898, 4. Aufl., pp. 180, 



