Meyen's Report for 1839 on Physiological Botany. 27 



only be effected, when the solution of a far greater puzzle, viz. 

 the construction of the spiral and its peculiar genesis, shall be 

 achieved ; and I would beg Mohl to direct his attention to 

 this, as I myself have done long since. Heartily should I re- 

 joice with him should it fall to his lot to solve this problem 

 as he has already done in so many other cases. 



VI. — Report of the Results of Researches in Physiological 

 Botany made in the year 1839. By F. J. Meyex, M.D., 

 Professor of Botany in the University of Berlin. 



[Continued from vol. vii. p. 471.] 



On the Evolution of Heat by Plants. 



A VERY beautiful series of experiments on tins subject has 

 been published by MM. G. Vrolik and W. H. de Vriese*; they 

 have continued their researches on the evolution of heat in 

 the spadix of Colocasia odora ; they were published at the end 

 of 1838, but we received the journals too late to be able to in- 

 sert them in our former Report. 



The above-mentioned observers express their astonishment 

 at the explanation given by M. Raspail of the evolution of 

 heat in the spacUx of the Aroidea, but add that their new ob- 

 ser\^ations were not made in order to disprove Raspail's view, 

 for that is not necessary. The first observations were made 

 with the spadix of Arum italicum ; they were made in the 

 open air, and no rise of temperature was observed : in the in- 

 terior of an orangery another flower exhibited a considerable 

 increase of warmth, and also when the light was shut out and 

 the spatha removed, still an increase of temperature took 

 place, as was to be expected. Moreover experiments were 

 made with the spadices of Colocasia odora under similar cir- 

 cumstances, both when the spadix was cut away and when 

 only turned back ; the maximum difference between the tem- 

 perature of the air and the interior of the spadix was 19|^ 

 Fahr. 



Moreover interesting experiments were made on the phe- 

 nomena exhibited by the spadices of Colocasia in different 

 gases, for which purpose a very excellent apparatus was con- 

 trived. The rise of temperature in two perfectly similar spa- 

 dices which happened to be in perfection at the same time 

 was obsened, one in the common air and the other in the 

 above instrument in an atmosphere of oxygen. The latter in 



* Tijdschrift voor Natuurl. Geschieden. en Phys., vol. iii. pp. 190 — 2.30 ; 

 also in Wicgmann's Archiv for 18.39, p. 1.3.5. 



