ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



52' 



the slide. The muslin is now moistened again, and afterwards carefully 

 removed. The sections may now be treated in the usual manner. 



Instead of water, alcohol may be used for imbedding. The tissue 

 partly dehydrated is placed in alcohol on a water bath, and soap added 

 till no more will dissolve. 



Fixation in Vacuo.*— W. J. V. Osterhout describes a simple air- 

 pump for removing air from vegetable tissues. The construction of the 

 pump is seen in fig. 118. A piece of glass tubing 12-15 inches long is 

 stopped at one end with sealing wax. A rubber 

 disc (r) is pushed about an inch down the tube, 

 and after carefully warming the glass, melted 

 sealing wax is poured in. The piston may be 

 prepared as follows : Insert a rubber stopper at 

 the unsealed end of the tube, press it in gently and 

 then cut it off cleanly just at the top of the tube. 

 In the upper half of the stopper make another cut 

 just above the first so as to slice off a disc about 

 ^ inch in thickness. With an awl make a hole 

 exactly in the centre of this disc and force through 

 it a brass rod about ^ inch in diameter and of 

 the form shown in the illustration. This should 

 be provided with a thread at the end and cany a 

 nut (n) above the disc and a nut and washer (w) 

 below it. The washer should be a little smaller 

 than the inside diameter of the tube. 



In order to use the apparatus the tissue is 

 placed in the tube and the fixative poured over it. 

 When the piston is pushed down the disc springs 

 back to allow the air to escape. When it comes 

 below the liquid it is pulled back, the result being 

 the production of a very good vacuum. In order 

 to inject tissues with fixative, the pieces are 

 secured by means of wire or wedges so that they 

 cannot rise in the liquid. The piston and the 

 inner surface of the tube are then coated with 

 vaselin to prevent the piston from sticking. The 

 piston should be forced down about \ inch below 

 the surface of the liquid and then drawn up 

 again, when the springs (s) will hold it in place. 



Fig. lis. 



(3) Cutting', including- Imbedding and Microtomes. 



Agar-Agar and Paraffin Method for Imbedding Plant Tissues.t- 

 H. H. York first kills tbe tissues, then imbeds in 2 and 5 p.c. agar 

 solutions, afterwards imbedding in paraffin in the usual way. To the 

 agar solutions 1 part of formalin to !> parts by volume of agar is added. 

 The tissues are placed in the '1 p.e. agar solution at 70° C. for two hours, 



* Univ. California Pub. Bot., ii. (1904) pp. 78-80 (1 lig.). 

 t Ohio Naturalist, v. '1905) pp. 344-5. 



