ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 719 



(2) Preparing Objects. 



M a bpmakh — Ueber die Preparation der Diatomaceen, Foraminiferen, Polycystineen 

 and Spongillen. Zeitschr. angew. Mikr., x. (1904) pp. 141-5. 



(3) Cutting, including: Imbedding and Microtomes. 



Agar Method for Imbedding Plant Tissues.* — H. H. York re- 

 commends the following quick and simple method for fixing and im- 

 bedding plant tissues. 10 grm. of agar are boiled in 500 c.cm. of 

 distilled water for 2 hours. The hot solution is poured into a tall 

 cylindrical vessel. When cold, the clear upper portion is cut off and 

 put into a glass jar. The jar is placed in a basin of hot water until 

 the agar is melted, and then 1 part of formalin is added to 9 parts by 

 volume of the melted agar. A 5 p.c. solution is prepared in a similar 

 way. The fresh tissue is placed in hut 2 p.c. solution for about 

 2 hours, and is then transferred to the 5 p.c. solution for an hour or 

 so, after which it is imbedded on wooden blocks. A layer of agar is 

 smeared on the block, and allowed to cool ; then the piece of material 

 is placed thereon and covered with a sufficient amount of agar. When 

 properly fixed to the block the whole mass is placed in 95 p.c. alcohol 

 for 12 hours, after which it is sectioned on a sliding microtome. 



Sectioning Wheat Kernels.f ■ — B. J. Howard soaks the grains in 

 90 to 1>5 p.c. alcohol for 10 to 14 days, after which 1)0 p.c. glycerin is 

 added to the alcohol in small proportions at intervals of a few days, 

 until the proportions of alcohol and glycerin are about equal. The 

 material is then allowed to stand until the grains have attained a firm 

 cheesy consistence. When the softening has attained a satisfactory 

 stage, the grains are placed in a shallow dish just covered with the 

 fluid. When the alcohol has evaporated (2 to 3 days) the grains are 

 treated (1) with 98 p.c. alcohol for 30 to 60 minutes ; (2) with chloro- 

 form, 30 to 60 minutes ; (3) chloroform and paraffin shavings, 60 to 90 

 minutes ; (4) melted paraffin, changing 2 or 3 times, for 2 hours ; 

 (5) block ; (6) sections. 



Imbedding Medium for Brittle Objects.J — J. T>. Johnston has 

 found that rubber mixed with paraffin wax makes a satisfactory medium 

 for imbedding brittle objects, such as amphibian embryos. Mix with 

 hard paraffin about 1 p.c. of indiarubber cut up into very small pieces. 

 Dissolve by heating to 100° C. (not more) for 24 to 48 hours, though 

 several days at from 55° to 60° will serve the purpose. Filter or use 

 the supernatant fluid. Keep a stock of the prepared mixture cold, as 

 the rubber separates out after a few weeks if the mixture is kept 

 melted. Use as ordinary paraffin, except that xylol and not cedar-wood 

 oil must be used for clearing. The hardened block is light brown, 

 and the melted solution is murky. This murkiness may be prevented 

 by dissolving in the paraffin before the rubber is added enough 

 " mineral rubber " (asphalt) to give the paraffin a light ami >er colour. 

 This paraffin-asphalt solution is more transparent than simple paraffin, 

 and so facilitates orientation of the object. 



* Journ. App. Micr., vi. (1903) pp. 2591-2. 

 t Tom. cit., pp. 2498-9 (1 fig.). X Tom. cit., pp. 2G02-:;. 



