224 



HEAT AND PROTOPLASM 



[Ch. VIU 



by a line which is slightly steeper at the higher temperatures 

 than at the lower. This change of steepness is, however, much 

 less striking in the case of the etiolated wheat seedlings studied 

 by RiscHAWi, where the following series was obtained: — 



The evidence from excretion thus also confirms the conclusion 

 that the metabolic processes are accelerated by raising the tem- 

 perature to a certain limit. 



The effect of heat in the metabolic process of chlorophyll 

 formation is shown in some plants upon which Sachs ('64) 

 experimented. He prepared three culture chambers, all illu- 

 minated by a north light. A was kept at a high temperature, 

 namely, 30° to 34° C. ; B was kept at a temperature of 16° to 

 20° C, and Cat 8° to 14° C. Into these chambers were put etio- 

 lated seedlings of Phaseolus multiflorus (bean) and Zea mais 

 (maize) which had been reared in the dark. The first traces of 

 turning green appeared in A after 1^ hours ; in B after 2 to 5 

 hours ; whilst in C no trace of greening appeared until several 

 days had passed. Thus it appeared that at the temperature of 

 8° to 14° C. chlorophyll is hardly produced. 



We now pass to the consideration of some Protista. An 

 indication, at least, that the rate of metabolism is increased 

 with temperature is gained from the increased rapidity of 

 formation of the contractile (excreting) vacuoles of Ciliata 

 under these conditions. Thus, RossBACH ('72, p. 33) found 

 that the rapidity of the rhythmic movements of the contractile 

 vacuole is most intimately related with the temperature of the 

 body, so that one and the same species of animal under normal 

 conditions always has, at a given temperature, the same number 

 of contractions. From the number of the rhythmic contrac- 

 tions one can therefore draw a certain conclusion concerning 

 the existing degree of temperature. This relation between 



