310 SUMMARY OF CURRENT RESEARCHES RELATING TO 



aro to bo thoroughly washed out with running water. The water is 

 then replaced by alcohol, which must be added gradually in increasing 

 strengths of 20, 40, GO, 80, 95 per cent., to prevent it swelling. The 

 alcohol is next replaced by a solvent of paraffin, turpentine being the best. 

 This is performed gradually, first with equal parts of alcohol and turpen- 

 tine, then with pure turpentine ; then transfer to a cold saturated solution 

 of paraffin in turpentine ; then to equal parts of turpentine and paraffin 

 kept at a heat of 30°-40° C. After an hour the temperature is raised to 

 50°-55° C, and the roots finally placed in pure melted paraffin renewed 

 once or twice. In about six hours the roots will be thoroughly per- 

 meated, and then they arc placed in rectangular moulds suitable for 

 being held in a microtome clamp. The inner surface of the moulds 

 should be wetted with turpentine before the melted paraffin is poured 

 in, and as soon as the molten mass is cooled so far that a film is formed 

 on its surface, cold water should be at once poured over it, as sudden 

 setting of paraffin prevents the formation of cavities. After the sections 

 are made they are glued to the slide with indiarubber solution, albumen, 

 or collodion ; the two last are to be preferred. If albumen, equal parts 

 of white of egg and albumen are mixed together, some drops of carbolic 

 acid added, and the whole filtered. If collodion, then a mixture of equal 

 parts of collodion and oil of cloves is made. In cither case the slide 

 is painted with the adhesive, the section pressed thereon, and the slide 

 is then heated in the oven for fifteen minutes at 50° C. While still warm 

 the slide is transferred to turpentine, which dissolves the paraffin, and 

 the turpentine removed by means of alcohol. 



The specimens may be stained before imbedding or as sections on 

 the slide. If the former, then Grenadier's alum-carmine when the 

 specimens have reached the GO per cent, alcohol stage ; if the latter, then 

 alum-carmine, hematoxylin or the anilins, the last being specially suitable 

 for demonstrating karyokinesis. 



The sections may be mounted in glycerin or balsam, but the latter is 

 preferable. 



New Imbedding Material.* — Prof. E. Pfitzer describes a new mode 

 of imbedding, which he has found very useful in the examination of 

 minute and very soft or thin parts of plants, such as the flowers of 

 orchids in early stages of their development. The principal objects 

 were to obtain an imbedding material which should combine solubility 

 in water with a great degree of transparency. These properties are 

 presented by glycerin soap. 



Prof. Pfitzer heats in a water-bath of a temperature between 60° and 

 70° C. a mixture of equal volumes of glycerin and 90 per cent, alcohol, 

 with as many minute yellow transparent pieces of glycerin soap as will 

 dissolve in it. This is best done in a cylindrical vessel stopped with 

 cotton wool, from which but little alcohol evaporates. The yellow 

 perfectly transparent or only slightly turbid fluid is poured either into 

 a flat dish or into a paper cup made by wrapping strips of paper round 

 a cork and fastening with a pin, the paper having been first saturated 

 with strong alcohol. While the mixture is hardening, the object must 

 be placed by a needle in a position suitable for making sections. With 

 larger objects it is convenient to insure perfect saturation by laying 

 them in a cold saturated solution of soap before transferring into the 



* Ber. Deutsch. Bot. Gesell. (Gen.-Versamml. Heft) v. (18S7) pp. lxv.-viii. 



