COLLECTION AND PRESERVATION Of 

 MATERIAL. 



Much of the material for work in histology must be collected 

 during the summer, or at times when it cannot be used at once, 

 and is therefore to be kept stored away until needed for study. 



Some difficulty must necessarily arise in the proper preserva- 

 tion of such material, but if special precautions are taken it can 

 easily be kept in good condition for histological purposes. The 

 methods of treatment vary with the nature of the material. 



All soft tissue collected, as, for example, leaves, herbaceous 

 stems, etc., should be placed at once in 40-50 per cent, alcohol and 

 hardened in the usual way by the use of a Schulze's apparatus, or 

 by transferring successively, for 24 hours in each, to. 50 per cent., 

 67 per cent., and 75 per cent, alcohol, in which it can be kept a 

 long time without deterioration. The softest tissues such as are 

 found in algae, etc., should be placed first in about 10 per cent, 

 alcohol and hardened by the use of Schulze's apparatus, or by 

 transferring, successively, for 24 hours in each, to 20 per cent., 30 

 per cent., 40 per cent., 50 per cent., etc., to 75 per cent, alcohol, 

 where they may be kept as in the case of the firmer tissues. The 

 material thus hardened when ready for use can be dehydrated with 

 95 per cent, alcohol, infiltrated with 2 per cent, and then 5 per 

 cent, collodion. In the latter solution it may remain indefinitely 

 without shrinking. If the tissue to be sectioned is kept on the 

 cork in alcohol, it will in time become discolored by the tannin of 

 the cork. 



The tissue of each sort should be trimmed until only such 

 parts remain as are needed for sectioning. These should be care- 



