RELATIONS OF PKOTOPLASM TO HEAT. 205 



are applied, the disorganized parts may become reunited, and 

 after a while the movement may begin again. No such recovery, 

 however, is possible when the protoplasmic mass has become 

 disintegrated by a high temperature ; the change thus produced 

 is practically coagulation. 1 



566. The temperature of certain hot springs in which living 

 algae have been found shows that protoplasm can bear without 

 injury a greater degree of heat than is indicated by the figures 

 in 561. Thus algae have been seen in the following thermal 

 waters : 



Temperature. Observer. 



Carlsbad 53. 7 C Cohn. 2 



Lip Islands .... 53. .... Hoppe-Seyler. 8 



Dax 57 Serres.* 



California Geysers . . 93 .... Brewer. 5 



Hoppe-Seyler found algae growing on the edge of a fumarole 

 where they were subjected to a temperature (from the escaping 

 vapor) of 60. 6 



567. That the protoplasm of many kinds of seeds and spores 

 can preserve its vitality during exposure to dry air at a tem- 

 perature above that of boiling water has been shown by many 

 experimenters ; 7 but unless the precaution is taken to remove 

 all water from the seeds by very careful and slow drying, any 

 temperature above 100 C. is injurious. Seeds thus cautiously 

 freed from moisture have been heated to 110, and even for a 

 short time to 120, without losing their power of germination 

 (see also "Germination"). Nor does there seem to be any es- 

 sential difference between the seeds which contain oils and those 

 which contain starch in their capacity to endure high tempera- 

 tures. Hoffmann 8 and Pasteur 9 have shown that the vitality of 

 perfectly dry seeds and spores mav in some cases be retained 

 until a temperature of 130 C. is reached. 



i Pfefier : Pflanzenphysiologie, 1881, ii. p. 386. 2 Flora, 1862, p. 538. 



8 Pfliiger's Archiv., 1875, p. 118. 4 Botan. Centralblatt, 1880. p. 257. 



6 Am. Journ. Sc. and Arts, 2d series, xli. 391. 



6 Pfliiger's Archiv., 1875, p. 118. 



A much higher temperature is noted by Humboldt ; namely, 85 C. for the 

 hot spring of Trinchera, Caraccas, in which he found the roots of certain plants 

 growing. 



7 Milne Edwards and Colin : Ann. desSc. nat., ser. 2, tome i., 1834, p. 264; 

 Sachs's Handbuch der Experimental- Physiologic, 1865, p. 65 et seq. ; Just, in 

 Cohn's Beitrage zur Biologie der Pflanzen, 1877, p. 311. 



8 Pringsheim's Jahrb., 1860, p. 324. 



9 Ann. d. Chimie et de Physique, 1862, p. 90. 



