434 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



spring water or glycerine kills the tissues very rapidly, 

 and the former more particularly causes ( a great swelling 

 up 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 

 hematoxylin ( 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 future examination, it should be fixed in a 1 per cent, 

 solution of picric acid in water. The material may remain 

 in this solution for a few hours, and is then washed in 

 50 per cent, alcohol, till the latter no longer becomes 

 yellow. Then remove it to TO per cent, and finally to 

 90 per cent, alcohol for preserving. Some glycerine 

 (about 25 per cent.) may be added, thus preventing the 

 sj:>ecimens getting too brittle. 



In order to cut sections with the microtome, the portions 

 of the plant to be cut must be embedded in paraffin. They 

 should be dehydrated in absolute alcohol, left in cedar- 

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

 ferred to paraffin at 55° C. They may be cast in a block 

 after about two hours. 



Permanent preparations are, however, useless to a 

 student, if similai sections have not been previously 



