600 SUMMARY OF CURRENT RESEARCHES RELATING TO 



this way stain perfectly well ; borax-carmine is to be preferred as a 

 staining agent. If imbedded in paraffin tliey give excellent sections. 



Preparing and Mounting Insects in Balsam.* — As it is difficult 

 in preparing many of the smaller forms of insects to remove the 

 debris from the surface of the specimen without injuring the delicate 

 portions, Mr.Leckenby uses albumen, flowing the white of an egg 

 over the object and immersing the slide in hot water till the albumen is 

 coagulated, when it will generally crack open, and may be removed in 

 two portions, carrying with it all the foreign matter and leaving the 

 surface of the specimen perfectly clean. He strongly advocates thorough 

 washing of the objects in running water and a final rinsing in either 

 filtered or distilled water before placing in alcohol. 



In mounting, the insect is placed under the cover-glass, arranged in 

 proper shape, the clearing solution applied, and when sufficiently trans- 

 parent the oil of cloves is cleared away and Canada balsam introduced 

 at one edge of the cover-glass, the slide being held over the flame of a 

 lamp to gently warm the balsam and allow it to flow in and displace the 

 remaining oil of cloves. No annoyance need be felt at the presence of 

 bubbles of air, as they will all gradually disappear. The mount, when 

 filled with balsam, is placed in a warm oven or incubator and kept at a 

 temperature of from 120° to 130° F. for twenty-four hours, when the 

 balsam will be thoroughly hardened and all the air-bubbles driven out. 



Mr. Leckenby does not advocate the use of volatile solvents with 

 balsam, being convinced that a certain amount of gas is always retained 

 in the mount in a latent state, requiring only a slight amount of heat to 

 produce bubbles and disfigure the specimen. 



Demonstration of Embryo-sact — Prof. D. H. Campbell recom- 

 mends Monotropa unijiora for this purpose, in consequence of the com- 

 paratively large size of the ovules and embryo-sac. It is only necessary 

 to strip away a small piece of the jDlacenta with the adherent ovules, and 

 mount in water or a 3 per cent, solution of sugar. In the latter fluid 

 the ovules remain unchanged for several hours, and may be studied at 

 leisure. The embiyo-sac is covered by only two layers or cells, and 

 these are perfectly colourless, not interfering in the slightest degree 

 with the view of the embryo-sac. 



Demonstration of Pollen-mother-cells and Pollen-tubes.:i: — Prof. 

 B. D. Halsted recommends for this jDurpose the young anthers of 

 Negundo aceroides. A section of the anther-lobe will be found to be 

 made up of a single ring of mother-cells, many of which are pear- 

 shaped ; and in these loose cells the four pollen-grains may be found in 

 all stages of development. At first there is only the slightest differen- 

 tiation of the protoplasm into four indistinct masses, which gradually 

 become more evident, their arrangement in the mother-cell varying. 

 Azorubin is excellent in weak solution for bringing out the young 

 grains more prominently. 



For the observation of the emission of pollen-tubes, the same writer § 

 places pollen-grains in a solution of sugar varying between 10 and 

 75 per cent. Species of Asclepias, for which the most favourable strength 



* Proc. San FranciBCO Micr. Soc, April 24th, 1889. 



t Bot. Gazette, xiv. (1889) p. 83 (1 fig.). J T. c, p. 109. 



§ Bull. Turrey Bot. Club, xvi. (1889) pp. 130-1. 



