OF WASHINGTON. 65 



the latter's view that cultivated trees were more susceptible to 

 the attacks of insects than were wild trees, and also that 

 insects bred in burned trees go of choice to cultivated ones. 

 The idea that cultivated trees, when properly cared for, are 

 more tender or more liable to attack, was very common but 

 fallacious. As a rule they were more vigorous of growth, 

 and, as a consequence, less subject to attack. 



Mr. Fernow sustained Prof. Riley in this view, and, while 

 agreeing with Mr. Schwarz in that the burning furnishes 

 favorable conditions for the multiplication of the beetles, he 

 held that cultivated forest trees were not especially liable 

 to attack unless they had been previously weakened and 

 injured from some other cause. 



In reply, Mr. Schwarz called attention to the frequent forest 

 fires and the consequent enormous multiplication of Scolytids, 

 which did not result in the overrunning of unburned areas 

 with these beetles. He said that in 1876, at Lake Superior, 

 he had seen on a large tract of burned white-pine land perfect 

 clouds of Pityophthorus puberulus and other Scolytids which 

 had developed in the half-burned trees, yet the adjoining 

 forest did not suffer subsequently. In the cultivated forests of 

 Europe a single acre left in such neglected condition would 

 bring destruction to a large extent of surrounding forest. 

 According to Mr. Schwarz, the only explanation of this differ 

 ence is that the wild forest trees possess a greater power of 

 resistance to the attacks of Scolytids, which is partly or 

 wholly lost in the cultivated trees of forest and orchard. 



Mr. Ashmead related his experience with Scolytids in Flor 

 ida orange groves, and agreed with Prof. Riley that cultivated 

 trees were equal, if not superior, to wild trees in their power 

 ot resistance to insects. He mentioned a case of an orchard 

 scorched by fire, in which a common Scolytid appeared the 

 following year in great numbers, and stated that the work of 

 these beetles always followed injury resulting from some other 

 source. 



Prof. Riley wished to be recorded as agreeing with Mr. 

 Schwarz' s conclusions, except as to the explanation of the 

 effect on cultivated trees of the burning of forests, accom- 



