KELATIONS OF PROTOPLASM TO HEAT. 205 



are applied, the disorganized parts maj' become reunited, and 

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

 however, is possible when the protoplasmic mass has become 

 disintegrated b3- a high temperature ; the change thus produced 

 is practically coagulation.^ 



566. The temperature of certain hot springs in which living 

 algiE have been found shows that protoplasm can bear without 

 injury a greater degree of heat than is indicated b}' the figures 

 in 661. Thus algse have been seen in the following thermal 

 waters : — 



Temperatare. Observer. 



Carlstad 53°. 7 C Cohn.^ 



Lip Islands .... 63° Hoppe-Seyler.' 



Dax 57° Sevres.* 



California Geysers . . 93° .... Brewer.^ 



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

 where they were subjected to a temperature (from the escaping 

 vapor) of" 60°.° 



567. That the protoplasm of manj' kinds of seeds and spores 

 can preserve its vitalit}' during exposure to dry air at a tem- 

 perature above that of boiling water has been shown by many 

 experimenters ; ' 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 cautiouslj' 

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

 short time to 120°, without losing their povver 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 capacit}- to endure high tempera- 

 tures. Hoffmann" and Pasteur^ have shown that the vitality of 

 perfectly dry seeds and spores may in some cases be retained 

 until a temperature of 130° C. is reached. 



1 PfefFer : Pflanzenphysiologie, 1881, ii. p. 386. 2 Flora, 1862, p. 538. 



8 Pfltiger's Arehiv., 1875, p. 118. ♦ Botan. Centvalblatt, 1880. p. 257. 



' Am. Journ. So. and Arts, 2d series, xli. 391. 



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



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

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

 growing. 



' Milne Edwards and Colin : Ann. desSe. nat., s^r. 2, tome i., 1834, p. 264; 

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

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



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



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



