Put half an ounce of cochineal, in powder, into half a pint of spirit of wine; set it in a warm place, and shake it often for four days; then filter off the clear tincture. Put an inch depth of this into a cup, and set upright in it pieces of the rind of ash, white willow, and ozier, prepared as has been directed, by maceration in water; for in that way one trouble serves for an hundred kinds. Let an inch of the rinds also stand up out of the tincture. After twenty-four hours take them out, clip off the part which was immersed in the fluid, and save the rest for observation.
Cut the pieces in a fit season, either just before the first leaves of Spring, or in the Midsummer shooting time. Then we see all the wonders of the structure; the thousands of mouths which open throughout the course of these innumerable vessels, to pour their fluid into the interstitial matter.
These vessels, which are in nature cisterns of sap for the feeding the growth of the whole tree, are so large, that they are capable of being filled with coloured wax, in the manner of the vessels in anatomical injections; and this way they present pleasing objects for the microscope, and afford excellent opportunities of tracing their course and structure.
A METHOD OF FILLING THE SAP VESSELS OF PLANTS.
A great many shoots of the scarlet and other oaks are to be taken off in the Spring; they must be cut into pieces of about two inches in length, and immediately from the cutting they must drop into some warm rain water: in this they are to stand twenty-four hours, and then be boiled a little. When taken out, they are to be tied on strings, and hung up in a place where the air passes freely, but the sun does not shine. When they are perfectly dry, a large quantity of green wax, such as is used for the seals of law deeds, is to be gently melted in an earthen pipkin set in water; the water to be heated and kept boiling. As soon as the wax runs, the sticks are to be put in, and they are frequently to be stirred about. They must be kept in this state about an hour, and then the pipkin is to be taken out of the water, and set upon a naked fire, where it is to be kept with the wax boiling for two or three hours; fresh supplies of the same wax being added from time to time.