336 
NOTES AND MEMORANDA. 
regard to tlio number of stomata, is sometimes with tbe superior face, 
and it is that which then gives the most strongly tinted impression. 
In this impression, as in that of the inferior face, the stomata are 
shown, arranged in a linear series parallel to the veins. 
3rd. Leaves with stomata on the superior surface only. The 
superior face alone gives an impression, although its cuticle is much 
thicker and much more strongly coated with wax than that of tho 
inferior face. 
The conclusion to be derived from these facts is the following : 
the leaves can emit aqueous vapours, both by the cuticle and by the 
stomata; in proj^ortion as they advance in their development, the 
exhaling power of the cuticle, which goes on diminishing, tends to 
become inappreciable ; when they are completely developed, it is by 
the stomatic orifices that the foliar exhalation takes place normally. 
The activity of the exhalation increases with the richness of tho 
tissues in chlorophyll. 
The exhalation of the aqueous vapours is equally produced by 
the stomata also.* 
Staining for the Central Nerve System . — In his ‘ Manual of Human 
Anatomy,’ Henle mentions a method of staining the central nerve 
system originated by Merkel, and which consists in placing the section 
first for one to two minutes in chloride of palladium (1 : 300-600), 
and then (after being washed) in Gerlach-Clarke’s carmine solution. 
In the course of my investigations, however, I found that a pigment 
recently produced by Dr. Witte, produced far more beautiful results 
with this method than the carmine solution. This substance is the 
picro-carminate of soda. The staining is very effective ; the ganglion- 
cells and the axis-cylinder are deep red, whilst the white substance of 
Schwann becomes a strong yellow ; the red, moreover, is a very 
2 ileasing soft carmine-red, and the yellow that of picric acid. Ordinary 
jiicro-carmine does not yield nearly such beautiful results. 
As regards the process, it is best to use cold saturated solutions 
of the 2 >icro-carminate of soda, as this on the whole only stains 
slightly. After the preparation has been let lie for about one to two 
minutes in the palladium solution, and then been rinsed, it is let 
remain in the jiigment solution some eight to ten minutes. Then 
varnished over. It must be admitted that a darkening of the palladium 
staining frequently occurs later on, whereby the |)reparations sufler if 
not sheltered from the light. 
The j)rocess is further very suitable for staining isolated ganglion- 
cells, and this is best done by using Ranvier’s alcohol. I confine myself 
to the use of Ranvier’s recipe, at least as regards the central nerve 
system ; his alcohol has done me better service than the maceration 
solution recommended by Deilers, and the carbolic acid lately recom- 
mended by Eichhorst in the ‘ Centralblatt.’ If into a moderate 
quantity (so much that the pre 2 )arations can lie easily in it) of Ranvier’s 
alcohol, fresh S23inal cord of the calf or ox be laid, in pieces of about 
half a centimetre thickness, for some days in a well-closed glass, you 
* ]\r. Merget, in ‘Comptes llendiis,’ vol. Ixxxvii. p. 293. 
