The Microscope. 307 



TECHNOLOGY. 



PREPAKING LACTAEIUS TO SHOW BRANCHED LACTI- 

 CIFEROUS VESSELS. 



D. A. Weiss finds [S. B. K. Akad. Wiss. Wien, xci. (1885)] that 

 pieces of Lacfarius deliciosus should not be kept too long in spirit, 

 and the sulphuric acid shows the course of vessels very plainly, the 

 contents of the tubes assuming quickly a blue-black color. The 

 surrounding tissue being greatly affected by the reagent, the latici- 

 ferous vessels appear still more clearly, slight pressure on the 

 cover-glass serves to separate them for some distance. Iodine- 

 water imparts to the tubes and their contents a trace of green, which 

 is rendered more intense by potash, and the juice appears in large 

 dark-orange colored drops. The color afterwards passes into brown. 

 Ferrocyanide of potash, sulphocyanide of potash and nitrate of silver. 

 bleach the juice. Platinum-chloride, cobalt-oxide, chromic acid, 

 and potassium-bichromate have no effect. Gold-chloride stains the 

 vessels blue-black, the hyphfe, greenish-yellow. Sulphuric acid 

 stains the contents of the vessels yellow, yellowish-green, greenish- 

 black, and finally blue-black; the contents of the hyphal filaments 

 rose-red. Iodine solution brings out a very dark, almost black, 

 color in the vessels. — Jr. R. M. Society. 



Cement foe Finishing Slides. — Mr. Thos. Lisle {Journal Mic- 

 roscopy) gives the following directions: Take dry white-lead (flake- 

 white) and crush it fine with a spatula, or old table-knife, add as 

 much turpentine as will make a thick paste, then grind fine. Some- 

 thing is then wanted to bind the color together when dry. Damar 

 or Canada balsam will do, but neither is as good as copal varnish. 

 Several kinds of this varnish can be had at the oil and color shops, 

 but for this purpose it must dry without heat and be free from 

 color. That which is known in the trade as lamp-head varnish is 

 the best, it dries in about two hours; cabinet varnish is good, but 

 rather longer in drying. Spirit varnishes are worthless for this 

 purpose, as they are brittle. About an equal bulk of varnish should 

 be added to the color; if less is used the work will look dull, if 

 more is used the color will be wanting in body. Before proceeding 

 to lay on the colored ring, it is a safe practice to j)ut on two or three 

 coats of something which will prevent running in. I have used two 

 coats of copal varnish, each to be well dried before laying on 



