SPECIAL METHODS 145 



material becomes white. Four or five minutes should be sufficient. 

 The fumes are disagreeable and are very injurious to microscopes. 

 Pour the contents of the tube into a dish of water. After the material 

 is thoroughly washed in water, it may be teased with needles and 

 mounted, or it may be put into a bottle of water and shaken until 

 many of the cells become dissociated. 



After a thorough washing in water, the material may be stained. 

 The large tracheids of ferns, dissociated in this way and stained in 

 safranin or methyl green, make beautiful preparations. 



JEFFREY'S MACERATION METHOD 



A method which I saw at Toronto and which gives much better re- 

 sults was credited to Professor Jeffrey. Wood is cut or split into sec- 

 tions about 300 fx thick, which are then boiled and cooled until free 

 from air. The macerating fluid consists of equal parts of 10 per cent 

 nitric acid and 10 per cent chromic acid. The time will vary with dif- 

 ferent woods, but is likely to be about 24-48 hours if the temperature 

 is about 35° C. When properly macerated the cells may be shaken 

 apart or are very easily teased apart. Before staining, the material 

 should be very thoroughly washed to remove the acid. A study of such 

 material is very valuable in modern anatomical work. 



Maceration methods which act in a few minutes are likely to be so 

 violent that fine details will not be preserved. 



PROTOPLASMIC CONNECTIONS 



As a rule, protoplasmic connections are not hkely to be seen in an 

 ordinary preparation. It used to be thought that the rather large 

 protoplasmic strands seen at the sieve plates of the pumpkin and other 

 Cucurbitaceae were exaggerated examples of protoplasmic continuity ; 

 but, as a matter of fact, the large strands do not extend entirely 

 through the plate. The real continuity, through the middle lamella, is 

 scanty and hard to demonstrate. 



Very satisfactory material for the demonstration of the connecting 

 strands is furnished by the endosperm of the Japanese persimmon, 

 Diospyros kaki. Usually, as you get this persimmon at the grocery 

 store, it is seedless, but occasionally it has seeds. Fix in 10 per cent 

 formalin, or in formalin-alcohol (10 c.c. formahn to 50 c.c. of 50 per 

 cent alcohol) ; or in glycerin-alcohol (equal parts 95 per cent alcohol 

 and glycerin) for a week. The endosperm of the American persimmon, 



