64 



Shortly after I commenced using this product, the prelimi- 

 nary results being so excellent, I called the attention of the 

 curators of several large herbaria to its advantages. At the 

 Field Museum of Natural History, an analysis of it was made 

 by Dr. H. \V. Nichols. This analysis indicates that the paste 

 is entirely free from the corrosive soluble sulphates and chlor- 

 ides that are commonly found in inverted starch pastes. It 

 does contain small percentages of free phosphoric acid and acid 

 phosphate of sodium. Dr. Nichols' tests indicate that it does 

 not discolor white paper and a two months' test indicated no 

 deleterious effect on either the specimens or the paper. He 

 suggested, however, the possibility that the corrosive acids may 

 in the course of years, damage the specimens. Judging from 

 the experience I have had with the product over a period of 

 two years, this possibility does not seem to be at all likely. 



In order to check the possible action of Special A Tin Paste 

 on delicate plant tissues, I selected the petals of about twenty- 

 five species of plants, representing yellows, pinks, blues, reds 

 and purples, dried them quickly to preserve the natural colors, 

 and then mounted them in parallel columns on white paper, 

 using ordinary fish glue for one set and an unusually large quan- 

 tity of Special A Tin Paste for the other. This test sheet was 

 exposed to the light of an ordinary laboratory for a period of 

 eight months and during a part of the time to direct sunlight. 

 Actual fading was practically the same in both sets. The only 

 colors affected at all by the paste were the blues and purples 

 and then only in very small areas where the petals had been 

 bruised in pressing; there was in such areas a tendency for the 

 blues and purples to turn red on account of the acid character 

 of the paste. This insignificant discoloration was immediate 

 and the areas affected showed no increase in size after the paste 

 was set. Otherwise there was no discoloration of the delicate 

 petals mounted with the paste, and no deterioration has been 

 noted. 



Special A Tin Paste is admirably adapted for mounting thin 

 plants, but with specimens having very thick stiff leaves it is 

 sometimes difficult to secure proper adhesion between the paste 

 and the plant. At the Gray Herbarium, where, following my 

 suggestion, it has been rather extensively used, this difficulty 

 has been overcome by using it in connection with Improved 



