EFFECT OF MOISTTTRE AND TEMPERATURE. 25 



tho t(>inpor!itiiiv iin-n'ascs. ForiiK'ily tlu> »;eiK'r:il comsimisus of ()[)iiiiuM 

 liiis Ix'iMi to iiiiiko this stjiteiiiont in tho ivver.se order that i.s, that 

 temperature exerts ti very harmful action on seeds if nuich moisture 

 be present. For comparatively hijrh temperatures the latter statement 

 would i)rohably suffice— at least it is not misleadino-, and in a certain 

 measure it is true; hut at the lowest known temp(>ratures, as well as 

 at ordinary temperatures, moisture is the controUin*;- factor, and in 

 order to be consistent it should likewise l)e so considered for hioher 

 temperatures — that is, within reasonable limits. 



That temperature is only of secondary importance is brouoht out in 

 the results ol)tained by a number of investigators. It has Ijeen well 

 established by Sachs," Haberlandt/' Just,'' Krasau,'' Isidore-Pierre,* 

 Jodin,-^, Dixon, ^ and others that most seeds, if dry, are capable of 

 germination after being subjected to relative!}' high temperatures for 

 periods of short duration. The maximum for most seeds is a tempera- 

 ture of loo" C. for one hour; but if the seeds contain comparatively 

 large (luantities of moisture they are killed at nuich lower tempera- 

 tures. It has been reported that lettuce seed will lose its vitality in 

 two weeks in some of the tropical climates where moisture is abundant. 

 Dixon has shown that if lettuce seed be dry it will not all be killed 

 until the temperature has been raised to 11-1^ C. 



In case of low temperatures the factor of moisture is of less impor- 

 tance, 3'et even under such conditions the moisture must not be exces- 

 sive or the injur}" will be cpiite apparent. But if seeds are well 

 dried it can safely be said that they will not be killed as a result of 

 short exposures to the lowest temperatures which have thus far been 

 produced. Our knowledge of the resistance of seeds to extremely 

 low temperatures is based on the experiments of Edwards and Colin,'* 

 Wartmann,' C. De Candolle and Pictet,' Dewar and McKendrick,^' 

 Pictet,^ C. De Candolle,'" Brown and Escombe," Selby," and Thiselton- 



«Handbuch d. Exp. Phys. d. Pflanzen, Leipzig, 1865, p. 66. 



spflanzenbau I, 1875, pp. 109-117; Abs. in Bot. Jahresbr., 1875, p. 777. 



cBot. Zeit., .3.3, Jahrg. 1875, p. 52; Cohn's Beithlge zur Biol, der Pflanzen, 1877, 

 2: 311-348. 

 ^ '/ Sitzungsbr. d. Wiener Akad. d. Wiss., 1873, 48: 195-208. I. Abth. 



'Ann. Agron., 1876, 2: 177-181; Abs. in Bot. Jahresbr., 1876, II. Abth., 4: 880. 



/Compt. Rend., 1899, 129: 89.3-894. 



f/ Nature, 1901, 64: 256-257; notes from the Botanical School of Trinity College, 

 DuV)lin, August, 1902, pp. 176-186. 



/'Ann. sci. nat. bot., ser. 2, 1834, 1: 257-270. 



i Arch. d. sci. phys. et nat., Geneve, 1860, 8: 277-279; ibid., ser. 3, 1881, 5: 340-344. 



JIbid., ser. 3, 1879, 2: 629-6.32;' ibid., ser. 8, 1884, 11: 325-327. 



^Proc. Roy. Inst, 1892, 12: 699. 



^Arch. d. sci. phys. etnat., Geneve, ser. 4, 1893, 30: 29.3-314. 



»abid., ser. 4, 1895, 33: 497-512. 



r'Troc. Roy. Soc, 1897-8, 62: 160-165. 



"Bui. Torr. Bot. Club., 1901, 28: 675-679. 



