Preparation and Mounting of Vegetable Tissues 177 



Warm the jelly carefully in a water-bath until it is 

 quite fluid. Warm a slide, take up a little jelly in a 

 dipping-tube, and place it on the slide ; now take up the 

 epidermis with a lifter and put into the jelly on the slide, 

 being very careful to avoid making any air-bubbles. Now 

 take the cover-glass and apply it to the surface of the 

 jelly, push down the cover with the point of a needle until 

 it is quite flat, and then set aside to cool. The above 

 process applies to all specimens that are to be mounted in 

 jelly ; but when tissues have been preserved in spirit they 

 must be soaked well in water before being mounted. 



Annular Vessels. Get some stem of maize, cut it into 

 pieces about half an inch long, and then cut again into thin 

 longitudinal slices ; place these in water until rotten. Now 

 put some of the broken- up material on a slide and examine 

 with a microscope ; pick out the annular vessels on the 

 point of a needle, place them in some clean water, and wash 

 well. Stain in a weak watery solution of acid green, and 

 after washing in water, mount in glycerine jelly. 



Scalariform Vessels. Treat pieces of the rhizome of 

 Pteris aquilina in exactly the same way as stem of maize. 



Spiral Vessels. Treat pieces of the stem of rhubarb in 

 the same manner as annular vessels. 



Raphides may be isolated, or they can be mounted, in 

 situ, in the tissues in which they occur. For the former, 

 take some leaves of cactus, stem of rhubarb, and root of 

 Turkey rhubarb, cut them up into thin slices longitudinally, 

 and place them in a jar of water, covered up to keep out 

 dust, and put away until the tissue has become perfectly 

 disintegrated. This will take several weeks, and the process 

 is more easily carried out by keeping the jar in a warm 

 place. When all the material has broken up, stir well with 

 a glass rod, and strain through a piece of coarse muslin 

 into a shallow vessel, such as a soup-plate ; stir up again, 

 and then allow to settle for a minute, so that the raphides 

 may fall to the bottom of the plate ; now pour away as 

 much of the dirty water as possible, add more clean water, 



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