296 ANNUAL OF SCIENTIFIC DISCOVERY. 



wero killed by immersing tlicm for a few minutes in strong alco- 

 hol, Avhich aids greatly in the extraction of water, but usually 

 turns the delicate kinds to an opa(jue, dull white color; but this 

 opacity disappears when they are put into glycerine, and the real 

 colors again appear. Many colors, however, quickly fade or turn 

 red in alcohol, so that such specimens must be put at once into 

 glycerine. Green shades usually turn red almost instantly in 

 alcohol. Specimens of various h'pidopterous larvae were also well 

 preserved in the same manner. 



The expense is usually regarded as an objection to the use of 

 glycerine. The best and strongest can be bought at about one 

 dollar per pound ; but recently I have been able to obtain a very 

 dense and colorless article at 42 cents per pound, which is entirely 

 satisfactory. As there is no loss by evaporation, the specimens 

 will keep, when once well preserved, if merely covered by it. 

 The expense for small and medium-sized specimens is not much 

 more than for alcohol. — A. E. VcrrilLy Yale College. 



CHANGE OF COLOR IN AUTUMNAL FOLIAGE. 



Mr. Joseph Wharton, in the "American Journal of Science" 

 for March, 1869, makes the following observations: — 



" If chorophyl, the green coloring matter of leaves, should be, 

 like many other greens, a compound color, it must have lor one 

 of its elements a vegetable blue, capable of being reddened by 

 acids. If the juices of leaves, kept in a neutral condition by the 

 vital force, or by alkaline matter brought in the sap from the 

 earth, should, when circulation ceases, become acidilied by the 

 atmospheric oxygen, those juices would then be capable of red- 

 dening the vegetable blue of the chorophyl. If, however, that 

 vegetable blue should be thus reddened, it ought to become blue 

 again when exposed to an alkali ; or, in other words, if green 

 leaves should be reddened in the autumn in the manner here suj;- 

 gested, by the unresisted action of the oxidizing atmosphere, they 

 ought to return from red to green if immersed in an alkaline 

 atmosphere.'' 



He exposed upon a staging, under a jzlass receiver with a cap- 

 sule containing ammonia, a variety of autumnal red leaves, and 

 had the gratification to perceive that in most cases the green color 

 was restored, — the leaves having a thin and porous cuticle under- 

 going the change most rapidly and completely, the restored green 

 color remaining from some minutes to hours. 



'* Frost probably plays no other part in causing the autumnal 

 tints, than merely to arrest the circulation by killing the leaves. 

 When a sharp frost occurs early in the fall, while the pulp of the 

 leaves is still full and plump, the red colors come out brilliantly, 

 because there is plenty of the blue substance to be acted ui)on by the 

 juices, then also abundant. When, on the other hand, the leaves 

 die slowly and are at the same time slowly dessicated in a late 

 and dry autumn, the pul]) becomes so meagre, and the skin so dry 

 and hard, that an abundant })n)duction of fnie red lints is impos- 

 sible, and brown, the color of decay, predominates." 



