202 BOTANICAL GAZETTE. 



ended and we no longer require the starch, protoplasm and chlorophyll. 

 Here the bleaching removes these substances and leaves us the mere skeleton 

 of parenchyma, fibers, ducts and the like, all cleared out and in better condi- 

 tion for clearer observation and hence better adapted to the use of a class. 



I should here add that few, if any, fungi or lichens should be bleached; in- 

 deed they will almost certainly be injured or destroyed by it. 



Bleaching fluid: — The best is Labarraque's solution. The object is to be im- 

 mersed in it and covered, for the double purpose of excluding dirt and pre- 

 venting the deterioration of the fluid by exposure to the air. How long it 

 should be kept there depends on circumstances. The best rule is to stay until 

 it is bleached, but 7io longer. 



When it is bleached the object should be removed and placed in water, 

 then in another water, then in water slightly acidulated with nitric acid, then 

 into water and alcohol, half and half; after which it may be removed and placed 

 in nearly pure alcohol where it is to remain until thoroughly translucent. If 

 the object is of firm texture and not likely to be injured by the water, a day or 

 two may be spent in the process ot washing out all the Labarraque's solution 

 before it is finally assigned to the alcohol. If on the other hand(as in ferns 

 where we desire to retain the sporangia and spores) it be more flimsy, the 

 process must be hastened and should not take more than a couple of hours. 



Unbleached Specimens. These are as a rule cross or longitudinal sections, and 

 in a general way we may say the thinner they are the better. It once was the 

 custom to bleach these and under certain circumstances we may still do so. 

 It will, however, remove the protoplasm, etc., and thus prevent any success- 

 ful study of the action of the cell contents as related to growth and to cell- 

 multiplication. I seldom bleach these now. Immediately that the section 

 is made, I place it in a weak mixture of alcohol and water, then grad- 

 ually increase the strength by adding alcohol. It is, however, to be 

 observed that in the object as cut and before being placed in the alcohol we 

 will find the protoplasm more or less diffused through the cell cavity, tend- 

 ing, however, to gather along the cell walls. The nucleus may be in the 

 center or on one side. When, however, it has been soaked in alcohol, the 

 protoplasm will be observed gathered into a more or less dense mass in the 

 center and the nucleus will then resemble a nucleolus. This must be rem- 

 embered in studying specimens which have been placed in alcohol. I do 

 not regard any of the means advised to pr .'vent this contraction of the 

 protoplasm around the nucleus as entirely satisfactory. 



The section is to be left in alcohol until it has become as clear as it 

 can be made. How long this will be depends entirely on the character 



