Apr. 1807.] BOTANICAL SOCIETY OF EDINBUKGH 55 



under a stain, as eosin, will be found injected to a 

 considerable distance. There is also a method of injection 

 by means of the filter pump (Darwin's rhysiology of 

 Plants, p. 87). But there are many specimens which do 

 not lend themselves to injection hj either of these methods. 

 I find the following simple method extremely useful both 

 for class purposes and for private work. The apparatus 

 once set agoing requires little attention, and a large 

 number of specimens for laboratory work may be injected 

 in succession in a short time with a minimum amount of 

 trouble. I submit a few sections of stems injection-stained 

 by this method, to show the amount of penetration it is 

 capable of giving.* The practical worker will, however, 

 find it useful for all kinds of plant members. 



To the end of a large glass funnel a length of india- 

 rubber tubing is securely wired. The funnel is fixed at a 

 convenient height, and the lower end hangs free eight feet 

 or more in length ; at the lower end is fixed a compressor 

 clip. The stem, air-dried (I show an Aspidium stem 

 injected after lying in laboratory for years), preserved in 

 spirit, or fresh (perhaps in many cases preferably the 

 latter), has its end cut smooth and circular, and securely 

 wired into the lower free end of the tube. In the case of 

 delicate stems, it is preferable to lute with Canada balsam 

 or asphalt to avoid crushing. A beaker is placed beneath 

 to catch the escaping fluid. The funnel and tube are now 

 filled with a weak aqueous solution of fuchsin, the compressor 

 clip removed, and the stem left to itself for a few hours. 

 At the end of that interval it will be found that a con- 

 siderable quantity of the stain has passed through the 

 conducting elements, staining them en route. One 

 advantage of using the living stem is that the stain is 

 pretty well confined to the conducting elements, and hence a 

 good differentiation staining may afterwards be obtained. 

 The compressor clip is again applied, and the stem removed 

 and transferred to a duplicate tube containing a solution 

 of weak picric acid. This washes out the stain held in 

 the conducting elements by capillarity, and darkens the 

 stained elements, and at the same time fixes the tissues. 



* AspiJum stem (air- dried) ; Cycas stem (fresh) ; Dracsena (spirit 

 material). 



