Detection of Maltose in Tissues of Angiospenns. 161 
The tissues become very much softened by the action of the 
hot alkaline fluid and it is then very difficult—often impossible—to 
remount them. 
As the reagent is an aqueous one, little resistance is offered to 
diffusion of the sugars from the cells, and so the distribution of the 
precipitate may not be a true indication of the previous distribution 
of reducing sugars. 
The crystallising of the liquid as the water evaporates entails 
a rapid remounting (when this is possible) and so makes comparative 
work inconvenient and tedious. 
Moreover the minute granules of copper oxide precipitated are 
not always easily observable. 
To a certain extent these difficulties are overcome in a method 
introduced by Senft. 1 This is based upon Fischer’s discovery of 
the formation of yellow crystalline osazones when sugars containing 
the aldehyde or ketone group are treated with phenylhydrazine in 
slightly acid solution. These osazones are easily visible, are 
insoluble in cold water, glycerine and dilute caustic potash, and in 
some degree are characteristic for the sugars from which they are 
produced. 
The reagent is made up, not with water but with glycerine, 2 in 
which sugar is very much less soluble, and which does not evaporate 
and allow crystallisation of the reagent. 
Phenylhydrazine hydrochloride and sodium acetate are dissolved 
separately in about ten times their weight of glycerine. Warming 
is advisable in order to dissolve the reagents satisfactorily, and the 
liquids should be filtered once or twice before use. 
In applying the method to examine the distribution of sugars 
a drop of each liquid is put on a glass slide and mixed with a mounted 
needle, and a section of the tissue is then cut ahd laid in the reagent. 
The section, which must of course be more than one cell thick, is 
covered with a glass slip, and the preparation is either left for future 
examination or is placed in an oven heated by a water-jacket, where 
it may be left for any desired time. 
Without heating, the reaction is slow and uncertain, and in 
comparative work it is preferable to heat the preparations and so 
1 Senft, E, “ Ober den microchemischen Zuckernachweis durch 
essigsaures Phenylhydrazin.” Sitz. d. k. Akad. d. Wiss.in 
Wien, Mathem.-Naturw. Kl., Bd. CXIII., Abth., 1, 1904, 
pp. 3—28; Bot. Centralbl., 1904, pp. 28, 29. 
2 Plasmolysis is thus produced, but appears to be of little conse¬ 
quence in actual practice. In any case comparison of structure 
can easily be made with fresh material. 
