OBSERVATIONS ON THE CALIFORNIA VINE DISEASE 123 
В. HISTOLOGY 
TECHNIQUE.—In studying the anatomy of the California vine 
disease I have employed the usual cytological methods. The 
diseased tissues were prepared and placed, with rare exceptions, 
in the fixing fluid directly in the field. 
The fixative that gave me the best results is one per cent. 
chromic acid. Flemming’s solution does not appear superior to 
chromic acid as a fixative, and labors under the disadvantage of 
blackening the tissues to such an extent that details are masked, 
and decoloration of the sections in hydrogen peroxide has to be 
resorted to to bring them out. Even then, however, the chromic 
acid material gives preparations superior in sharpness and con- 
trast. Sections made from alcoholic material give stained prepa- 
rations that compare favorably with those obtained from chromic 
acid material. Though alcohol is not so good a fixative as 
chromic acid, I believe that it may nevertheless be advantage- 
ously substituted for it in many cases. The matter occluding the 
cell lumen in diseased tissues contains tannin, and is more or less 
darkened by the latter fixative, which is quite a disadvantage in 
all but very thin sections. 
After fixing, the tissues were washed, passed into alcohol and 
through bergamot oil into paraffin; or, if working partly in the 
cold, from alcohol to chloroform, in which the paraffin was dis- 
solved to saturation. Finally the chloroform was evaporated 
off at бо degrees Centigrade. 
The stain that gave me the best results for general purposes is 
acid fuchsin, a concentrated aqueous solution of bichromate of 
potash being used as the differentiator. This stain, prepared by 
dissolving 20 grams of acid fuchsin in 100 cubic centimeters of 
aniline water, gave me the best results when used in the fol- 
lowing manner: 
The sections to be stained, previously fixed to the slide, were 
covered with warm acid fuchsin, which was kept steaming hot, 
but not boiling, for a few minutes. The sections were then 
washed and plunged into warm bichromate, washed again m 
Water, and mounted. 
* Cf. Zimmermann, Botanical Microtechnique, 197. 1893. [Humphrey trans.] 
