BOTANICAL TECHNIQUE 631 



Chowdhury {An72. Bot., xlviii, 1934, p. 308) shortens the process 

 by keeping the material in HF in unstoppered gutta pereha 

 bottles, in a pressure cylinder. 



1254. Jeffrey's Vulcaniser Method (Bot. Gaz., Ixxxvi, 1028, 

 p. 4:56). Soften tissues in a dental vulcaniser at a temperature 

 of about 320° F. (160° C). The time required varies — a three to 

 four years old oak twig needs one hour, a piece of seasoned oak 

 four to five hours. Brass piping (| to 1 inch diameter) is cut into 

 lengths to fit the vulcaniser, and the ends are threaded for brass 

 caps. On one end the cap is made tight by sweating lead solder 

 into the thread. The other end is made tight by putting into the 

 cap a piece of cardboard and, on top of the cardboard, a piece of 

 lead. Place the tube in a vice, put the water or alcohol with the 

 material into the tube and screw the cap tight with a wrench. 



After vulcanising, cool the material slowly and then treat it 

 for a few days in a mixture of 2 parts water and 1 part hydro- 

 fluoric acid. Wash well, dehydrate and preserve in equal parts 

 of 95 per cent, alcohol and glycerin until needed for cutting. 



Jeffrey cut transverse sections of coconut shells and hard woods 

 as thin as 2 to 3 fi. 



1255. Williamson's Cellulose Acetate Method {Ann. Bot, 

 XXXV, 1921, p. 139). Transfer material, free of all air, from water 

 direct to pure acetone for one to two hours and then to a 12 

 per cent, solution of cellulose acetate in acetone for a period 

 depending on the hardness of the wood. The material is both 

 softened and imbedded by this method. Soft woods require two 

 days as a minimum, oak and beech at least six days, very hard 

 woods about fourteen days. Staining is unaffected by the treat- 

 ment. 



1255 bis. Kisser {Cytologia, v, 1934, p. 520) finds that blocks 

 1 X 1 X o- cm., kept in 96 per cent, alcohol saturated witli phenol, 

 at 60° C. over a water bath, are rapidly softened. 



1256. Kisser's Steam Method {Zeit wiss. Mik., xliii, 1926, 

 p. 346) consists, essentially, in allowing steam to play upon the 

 block as the sections are being cut. A 300 c.c. conical flask half 

 filled with water and heated from below by a Bunsen burner, is 

 fitted with a rubber bung through which passes a thistle funnel 

 and a bent glass tube. The thistle funnel dips well below the 

 water level and is used for refilling the apparatus. The bent 

 glass tube conducts steam from the flask to the block. The tem- 

 perature of the steam should be about 90° C. If too hot, the 

 steam dries the material, and if much cooler than 90° C. little 

 advantage accrues. Kisser cut transverse sections 5 mm. square, 

 of ebony, and sections of coconut shell 2 mm. square and 6 /x 

 thick. 



It is an advantage to boil the pieces of wood, cut into small 

 blocks of suitable size for sectioning, for twenty-four hours. Then 



