13 



HAEDE A / M i AG K XT8. 



hardening. From this strength it is transferred to 50 per cent., 65 

 per cent., 75 per cent., 85 per cent, and 1)5 per cent, alcohol 

 respectively, allowing it to remain in each solution for about 24 

 hours, varying the time according to the nature of the tissue. If 

 it is desirable to preserve the tissue for future examination, the 

 hardening should cease with the 75 per cent, strength, and in this 

 it should be kept until needed, when the hardening may be com- 

 pleted with the 85 per cent, and 95 per cent, strengths. 



A very convenient apparatus for hardening plant tissues was 

 invented by Schulze, and a modified form of it is recommended for 

 laboratory purposes. It can be made as follows: 



Fig. 1. Dehydrating apparatus. 



Fig. 1. Apparatus complete, showing dehydrating tube It in place. A. 

 plaster of paris diaphragm. C. Glass rod supporting the 

 disk. 



Fig. 2. Dehydrating tube. D. Chamois skin diaphragm. E. Spring 

 holding the diaphragm in place. 



In a 9x9 Whitall-Tatum museum jar a disk of plaster of paris 

 is supported about 5 c. m. from the top by means of legs made of 

 glass rods. The disk is perforated to allow tubes of various sizes, 

 from 2-4 c. m. in diameter to pass through. These are the B.Q- 



