210 



for valerianic acid in the usnal way with neutralized soda-solu- 

 tion upon sesquichloride of iron, no red precipitate of valerian- 

 ate of iron was formed, nor have I obtained a bluish-white 

 opalescent liquid of butyrate of copper on adding acetate of 

 copper. Uric acid was also found to be absent, on treating 

 with nitric acid and ammonia in the usual way ; neither could 

 I detect formic or acetic acid, nor did boiling with caustic soda 

 llbarate ammonia. A few drops of the secretion, put on a piece 

 of dry caustic soda, turned at first dark green, became in a few 

 seconds dirty brown, and cleared up to a brownish red after 

 several hours. So far I am not aware of the constituents of 

 the secretion, and, on sending some of it to Prof. Chandler, 

 asking his kind advice, I was told that a payment of sixty to 

 seventy-five dollars, in advance, would be necessary to have an 

 accurate analysis made. 



The secretion was gathered gradually, by holding live speci- 

 mens into a test-tube containing 10 grams of dry caustic soda. 

 About 60 drops have accumulated during a period of three 

 months. Carl F. Gissler. 



Attacks of Native tnsects upon Imported Trees. 



It is often stated that foreign trees, and other plants imported 

 into a country, are not attacked by the insects peculiar to the 

 new surroundings. The presumed immunity is even quoted as 

 an advantage in the use of such trees for forest trees. But the 

 immunity is apparently only presumed, at least for plants and 

 trees after their entire acclimatization. When I was a boy I 

 saw extensive plantations of Pinus strobus and of Robinia 

 pseudacacia, which grew excellently and seemed not to be at- 

 tacked by native insects. This was between 1824 and 1830, 

 Later, things have changed considerably ; nevertheless Ratze- 

 burg contends that at least deciduous trees are attacked less 

 (as he states it to be a common fact) than pine trees. There- 

 fore exotic oaks near by indigenous ones infested by Chrysomela 

 and Tenthredo are attacked less. The Pinus strobus accord- 

 ing to Noerdlinger, is attacked even more than European pine, 

 being damaged together by Scolytus polygraphus^ S. piniperda, 



