W. H. GILBCKT ON THE STAINING OF VEGETABLE TISSUES. 



For the first, transfer the section from alcohol to ma.eenta dye, in 

 which let it remain for about twenty minutes, then soak in alcohol 

 till the colour is removed from the parenchyma : next place it for 

 about one minute in the blue dye, shake it in alcohol for a few- 

 seconds, then in absolute alcohol for a few seconds ; from th:- . - 

 move to oil of cloves, in which allow it to remain till quite clear ; 

 after which place it in clean oil of cloves for about ten minutes. It 

 is now ready for mounting in balsam, the best form of which to use 

 is balsam in benzole. 



Dr. Beattv recommends the use of benzole after the oil of cloves, 

 in order to hasten the drying of the slide ; but this most certainly 

 injures all soft tissue, and therefore I have not used it : but instead 

 have adopted the following plan : — 



Removing the object from the oil of cloves, and draining away as 

 much as possible, I place it on a glass slip, and covering it with a 

 small quantity of balsam, allow it to stand for a short time pro- 

 tected from the dust. The effect is this — the balsam being denser 

 than the oil which occupies the cells, endosmose is at once set up, 

 and a large proportion of the oil is given out by the tissue, the 

 balsam taking its place. By tilting the slip, this mixture of oil and 

 balsam very readily runs off. Then drop on carefully at one side of 

 the object some fresh balsam, put on the covering-glass and leave to 

 dry. Do not apply heat. 



For staining by single immersion, to twelve drops of the blue dye 

 add seven of the magenta, and thoroughly mix. Into this purple colour 

 place your section for about one minute, remove to alcohol ; shake 

 well for a few seconds, then proceed as by former method. 



It matters not which process is employed, the result is always the 

 same ; and we must conclude that true selection takes place. 



The disposition of the colours is invariably this — the magenta 

 goes to the woody fibre, vessels, and bast tissue ; the blue to the 

 parenchyma, cambium layer, and medullary rays : the pith and 

 suberous layer of the bark being usually neutral. 



In other words, according to the generally received doctrine con- 

 cerning the circulation of the sap, those parts which are concerned 

 in the distribution and appropriation of the elaborated sap, take 

 blue, the remainder consisting of mature material, taking magenta. 



In very young stems, the pith also, without doubt, takes an active 

 part in the plant's economy ; consequently it then stains blue ; and 

 from this we have all gradations, till just that portion next the 



2 B 



