von Schrenk — Trees of St. Louis as Influenced by Tornado. 37 



Bohm and Breitenlohner,* Becquerel,t Krutzsch,^ find the 

 internal temperature of a healthy tree normally lower than 

 that of the air, but later researches have shown that, as a rule, 

 the temperature of the layers under the bark is higher by 

 several degrees than the surrounding air. Raraeaux § finds 

 that in a poplar branch, 4 cm. in diameter, the internal tem- 

 perature was 4°, 8°, and 13° C. warmer than the outside air. 

 Ihne || finds the maximum air temperature at about 3 P. M. 

 to be always below that of the tree, often many degrees. 

 Vonhausen ** measured the temperature of a large number of 

 beeches under varying conditions and computes the maximum 

 temperature on the W. S. W. side between the bark and wood 

 120° F. with an air temperature of 91°. He emphasizes the 

 fact that tender cells, like those of the cambium, cannot with- 

 stand so high a temperature for along time. Russell ft says; 

 " The temperature of the tree as a general rule ranged higher 

 than the outside." When the leaves were removed from a 

 tree of Abies balsamea the temperature between the wood 

 and bark wa3 4-5° higher than in an uninjured tree. Ram- 

 eaux records a similar increase in temperature in trees whose 

 branches had been removed, amounting to 8-10° C. Hartig 

 explains this increase by " the fact that the trees had small 

 crowns, and that little water found its way into the younger 

 wood rings.' ' %% The trees in which for some reason the 

 transpiration current had been stopped or much reduced 



* Bohm u. Breitenlohner, Die Baumtemperatur in ihrer Abhangigkeit 

 von ausseren Einflussen. Wiener Akad. Sitzber. d. math. nat. Classe 

 75:615. I. Abth. 



t Becquerel, Compt. Rendus etc. 47: 717. 1858; 48: 764. 1859. 



X Krutzsch, H. Untersuchungen iiber die Temperatur der Baume etc. 

 Kon. Sach. Akad. f. Forst u. Landwirte zu Tharand 10. 1854. 



§ Rameaux, M. Des temperatures v£g6tales. Ann. d. Sci. nat., Bot. 

 19:1. 1843. 



|| Ihne, Egan. Uber Baumtemperatur unter der Einfluss der Insola- 

 tion. Allg. Forst u. Jagdzeit. (Supplement) 12. Heft 4. 



** Vonhausen, W. Untersuchung iiber den Rindenbrand der Baume. 

 Allgem. Forst u Jagdzeit. 49: 8. 1873. 



ft Russell, H. L. Observations on the temperature of trees. Bot. Gazette 

 14:216. 1889.— See also Hess, Uber den Rindenbrand. Forstschutz 541- 

 49. 1878. 

 XX Hartig, R. Diseases of Trees (tr. by Somervllle & Ward) 295. 1894. 



