spriiifr water or g^lyceriue kills tlie tissues very rapidly, 

 and the former more particiilarly causes a great swelling 

 u]) of the cell walls, whereby the appearance of the tissues 

 becomes very much distorted. Iodine should frequently 

 be employed to test for the presence of starch. For this 

 purpose dissolve some crystals of potassium iodide and 

 some of iodine in water. 



Permanent preparations may be made by putting a 

 freshly cut section into dilute glycerine, and thence into 

 glycerine jelly. Sections may be stained in a solution of 

 lirematoxylin ( 1 per cent, solution in water), and then 

 mounted in glycerine jelly. When stained, sections can 

 also be permanently mounted in Canada balsam. To this 

 end they should, after staining, be dehydrated in absolute 

 alcohol, and after replacing the alcohol by xylol, they are 

 mounted in Canada balsam, which has previously been 

 dissolved in xylol. 



If it is intended to preserve some material in a bottle 

 for futui-e examination, it should be fixed iu a 1 per cent, 

 solution of picric acid in water. The material may remain 

 in this solution foi' a few hours, and is then washed in 

 •3(1 per cent, alcohol, till the latter no longer becomes 

 yeUow. Then remove it to TU per cent, and finally to 

 90 per cent, alcohol for })re:ierving. Some glj'cerine 

 (about '-io })er cent.) may be added, thus preventing the 

 specimens getting too brittle. 



In order to cut sections with the microtome, the portions 

 of the plant to be cut must be enibeddeil in paratfiu. They 

 should be dehydrated in absolute alcohol, left in cedar- 

 wood oil till they are quite transparent, and then trans- 

 ferred to paraflin at 55° C. They may be cast iu a block 

 after about two hours. 



Permanent preparations are, however, useless to a 

 student, if s'milai sections have not been previously 



