THE HEAT PRODUCED BY LEAVES 



MILDRED SPARGO 



Missouri Botanical Garden, St. Louis, Mo. 



In the spring of 1911 my attention was called to an article 

 in the Botanische Zeitung for December, 1908, by Hans Molisch, 

 "Ueber hochgradige Selbsterwarmung lebender Laubblatter," 

 in which he gave an account of his experiments on the heat pro- 

 duced by leaves'. He took every precaution to prevent loss of 

 heat by radiation and transpiration, packing the flasks contain- 

 ing the leaves in sawdust, and keeping them in a cooi room. 

 He obtained some remarkable rises in temperature, which he 

 attributed mainly to respiration, partly to chemical changes, 

 and, in those cases where the temperature rose far above the 

 thermo-death point, to "tote-oxidation." He also mentions 

 ferments and enzymes as possible sources. In all cases he con- 

 tinued reading the temperatures until he obtained a second rise, 

 which he interpreted as being due to the growth and work of 

 microorganisms. 



His experiments are interesting, and his statements well borne 

 out by the results obtained from them. His theory, that the 

 production of heat by leaves, whether attached, or detached 

 from the mother plant, is due almost solely to respiration has 

 been generally accepted, and certain interpretations of respira- 

 tion by some investigators are based largely on his results and 

 the conclusions therefrom. A general summation of his experi- 

 ments is best stated in his own words; — "lebende frische Laub- 

 blatter vieler Pflanzen, vom Sprosse abgetrennt und in grosseren 

 Massen beisammenliegend, sich binnen wenigen Stunden, ohne 

 Intervention von Microorganismen, hochgradige erwarmen, oft 

 so stark, dass sie infolge der selbst erzeugten Warme vom Tode 

 ereilt werden." 



277 



THE PLANT WORLD, VOL. 15, NO. 12, DECEMBER, 1912 



