BOTANICAL GAZTETE. 67 



stantly. I then examine it under a one-inch objecti^'C, to determine 

 whether the exact point where the blue and the red remain distinct 

 has been reached. If the blue has not occupied all the softer cells, I 

 take another section, and put it through the same process, counting 

 twelve, and so on, until the proper point is reached ; or on the other 

 hand, decreasing the count, if the blue has infringed upon the red in 

 the more dense tissue. Having thus determined the count for the sec- 

 tions of that particular material, I pass the remainder ot my sections 

 through the blue into the alcohol, merely counting off the immersion 

 of each section. I then place the sections for a few moments in ab- 

 solute alcohol, which seems to fix the colors, then through oil of 

 cloves into benzole, and mount in damar and benzole. It is some- 

 times advisable, with delicate tissues, to merely rinse off the blue in 

 95 per cent, alcohol and fix the colors in absolute alcohol, but every 

 operator will learn the minor details for himself in the manipulation. 



Of course, with the "rule of thumb" method of counting off the 

 time, slight variations will occur, which will mar the beauty of the 

 finished product; besides which minute differences in the thickness of 

 the section will affect the result, and even a distance of a quarter of 

 an inch in the same stem will make a difference in the density of the 

 tissue, which will be obvious in the sharpness of the colors under the 

 objective. So that the operator should not be disappointed if, out of 

 a dozen slides, only four should be worth preserving. The others can 

 go into the borax pot to be cleaned for another operation. However, 

 the beauty of those which do pass inspection, will amply repay for 

 the labor on the spoiled ones. I have perhaps been needlessly minute 

 in the description of the process I have employed, but I have been so 

 often hampered for the lack of minuteness in descriptions of processes 

 by others, which I have been endeavoring to carry out, that I deem it 

 better to err upon the safe side, even at the risk of being considered 

 dry or prosy. 



One word as to the use of eosin. I was attracted to it by its ex- 

 quisite purity of color under transmitted light, and its perfect trans- 

 parency. I found that sections preserved in its solution, always re- 

 tained their transparency, and did not become clogged or thick with 

 color, so that when taken out after months of immersion, the most 

 dense cells were no deeper in color than the solution itself So far as 

 regards its hold upon the tissues, it is as strong as roseine, or any of the 

 heavier colors I have ever tried. I cannot testify as to its permanence, 

 but I have some slides that were prepared over a year ago, that ap- 

 pear to be as bright and pure, as when they were mounted. Con- 

 trary to the experience of some others, I have not found that the ben- 

 zole has any bleaching effect, and I have used it with damar, in prefer- 

 ence to the usual balsam. Slides prepared with damar, however, 

 should have a thick ring of varnish around them as the damar is brit- 

 tle, and should not be trusted alone, to hold the covering glass. — W. 

 in American Microscopical Journal. 



Does Chlorophyll Decompose Carbonic Acid? — The recent 

 memoirs of Pringsheim (Untersuchungen uber das Chlorophyll) sug- 



