REAGENTS • 25 



box under the tap. In the botanical laboratory at Woods Hole, 

 Massachusetts, large quantities of material are washed at one time by 

 using an ordinary washtub with the bottom arranged as just described 

 for the box. If one is using such a large box or tub and does not need 

 all the streams of water, the tubes not in use may be closed by means 

 of clamps. 



Where running water is not available we should recommend the 

 washtub, as just now described. The tub could be filled, and, with a 

 single lot of material, would run for 10 or 12 hours. 



With delicate filamentous or branching algae and fungi, extreme 

 care must be taken in the washing, for the material must not get 

 tangled. Put some material — not too much — in a large Petri dish, 

 propped up on an inverted dish and tilted just enough to let the water 



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Fig. 14. — Washing delicate filamentous and branched material 



run off gently. As a precaution, the supporting dish may be placed in 

 a larger dish (Fig. 14). The stream of water should be from a pipette 

 fastened in the end of the rubber which has been slipped over the 

 water faucet. Drops of water are even better than a small stream. 

 Although some objects might be washed in 10 or 12 hours, it is better 

 to wash for 24 hours. Nothing would be damaged by the longer time 

 and subsequent processes, especially staining, might be improved. 



Everyone has his own chromo-acetic acid formulas. Some of those 

 in more general use are the following: 



a) Stock chromo-acetic solution. — 



Chromic acid 1 g. 



Glacial acetic acid 1 c.c. 



Water 100 c.c. 



This solution has been used quite extensively in embryological work 

 upon the higher plants. It fixes thoroughly, but often causes plas- 

 molysis in cells with large vacuoles. 



