THERMOTROPISM IN ROOTS 153 



were heated as high as 50° C, and with Zea Mays as high as 49° C. 

 In the present experiments, it was endeavored to keep the tem- 

 perature of T' in the neighborhood of 40° C. to avoid hurting 

 the roots. 



Thermotropism therefore does not occur in roots. Our concep- 

 tion of this term must be confined to the reactions of. sprouts, as 

 described by Wortmann and confirmed by Steyer and of peduncles 

 and flower-stalks which have been shown by the researches of 

 ^^oechting and Pohl to be thermotropic. Thermotropism in the 

 sense made useof byPorodkoisinrealitytraumotropism. Hesays^^ 

 in fact that '^ negative thermotropic and thermo-traumatropic 

 reactions are distinguished only by the intensity and stability of 

 the albumen coagulation conditioning them." 



SUMMARY 



1 . The use of a 1 j per cent solution of agar as a medium for the 

 roots, effectually excludes all factors except the difference of 

 temperature, but allows the roots to grow and bend. 



2. No thermotropic reactions occur when agar is used. 



3. The reactions in roots due to thermotropism according to 

 Wortmann, or to caloritropism according to Klercker, must be 

 explained by positive hydrotropism. 



4. Traumatropism assists the reactions resulting at higher 

 temperatures. 



-^ Porodko, Th. IM. loc. cit. 1913. P. 24S. 



