558 



The Museum Gazette 



The causes of such forms of death as we are contemplating 

 may be fairly classified as follows : — 



(1) Exposure to severe cold. 



(2) Exposure to heat, as from fires. 



(3) Drought. 



(4) Exhaustion of the soil — overcrowding. 



(5) Poisoning of the soil. 



(6) Attacks of fungus — (1) on the roots; (2) on the stem ; 

 {3) on the leaves. 



(7) Lightning strokes. 



These causes of danger may be divided into those likely to 

 act slowly and those which would be sudden. In the former 

 may be placed 1, 2, 3 and 7, for it is presupposed that the 

 tree is grown in a climate that suits it, and that it is not likely 

 to be hurt by any ordinary seasonal changes. When, however, 

 extreme cold occurs, and especially in exposed situations, 

 vigorous and healthy trees may be frozen or chilled beyond 

 recovery, and may be found in the spring to be either unable 

 to renew the distribution of sap, or doing so with such 

 feebleness that they are sure to succumb next winter. The 

 probability that cold has killed a tree is much increased if 

 others of the same kind have suffered, and if those have 

 suffered most which were most exposed. When cold injures 

 a tree it does so by its influence on the branches and leaves, 

 if any present, not on the roots. 



[The above fragment must stand as the introduction to a 

 series of papers on the causes of death of trees which we have 

 in preparation. — Ed.] 



