BULLETIN OF THE BUSSEY INSTITUTION. 99 
fungi, and the fact observed by Muntz * and by Bourquelot f that 
this mannite is a product of the transformation of sugar (treha- 
lose) during the ripening of the mushrooms, or even during the 
process of drying fresh young mushrooms, suggests the enquiry 
whether mannite may not be formed habitually in some flowering 
plants at those stages of development when the vital processes 
within the plant most nearly resemble those habitual to the mush- 
room. It would be of interest, also, to learn whether mannite 
and mannan are apt to be found accompanying one the other in 
those plants or parts of plants which habitually contain mannan. 
A Methodical Test for Mannite. 
The first point to be attended to was manifestly the devising of 
a test for mannite which should be trustworthy and more readily 
applied than the old plan of obtaining actual crystals of mannite, 
and studying their properties in comparison with those of pure 
mannite. ‘The idea lay near at hand that it should be easy to 
convert any product supposed to be mannite into mannose by way 
of oxidation, and to precipitate this mannose in the characteristic 
form of mannose-hydrazone by means of phenylhydrazin. 
On trial, it appeared at once that mannite may readily be changed 
to mannose by means of hydrogen dioxide acting in presence of 
a trace of ferrous sulphate, and that the mannose thus formed 
may easily be detected by means of phenylhydrazin. For ex- 
ample, an aqueous solution that contained 0.6 grm. of mannite 
was treated with a small quantity of ferrous sulphate and 10 ce. 
of commercial hydrogen dioxide (the commercial 3% solution of 
the United States Pharmacopeia) and left at rest for half an 
hour. ‘The mixture was then made faintly alkaline with sodium 
carbonate and filtered. The filtrate, acidulated with acetic acid, 
was evaporated to soft dryness, the residue was taken up with 
1 cc. of water, and the solution was filtered. To the dark-colored 
filtrate 16 drops of a solution of phenylhydrazin acetate were 
added, and in the course of five minutes balls of mannose hydra- 
zone appeared. Under the microscope many of these balls were 
* Comptes Rendus, 76. 649; 1874, 79. 1182; and Annales de Chimie et 
de Physique, (5.) 8. 60. 
+ Comptes Rendus, 108. 568; 1890, 111. 534, 578, and Journal de Phar- 
macie, 1893, (5.) 27. 113. 
