IO MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 
poses, since the natural brown hue of the lignite serves as an admir- 
able natural stain. Often, even in thin sections 5 and том in 
thickness, which are readily secured by the above method, the hue 
is too intense for the resolution of fine details. In such cases the 
sections may be very readily bleached by the use of chlorine water, 
which acts very quickly and without injury to the material. Per- 
oxide of hydrogen was also employed for this purpose but 15 not at 
all satisfactory as a bleaching agent for lignites. When the sections 
are of the desired shade they are dehydrated by means of absolute 
alcohol, to which a few drops of chloroform have been added to pre- 
vent the softening of the celloidin matrix which holds the sections 
together. Thence they are transferred to benzol or xylol for 
clearing and are mounted in Canada balsam. It is necessary on 
account of the use of photographic methods of reproduction to have 
the sections perfectly flat. This is effected by allowing them to set 
under weighted cover-glasses in a warm place. Subsequently they 
are subjected to still further pressure by means of photographic clips, 
which are prevented from breaking the thin cover-glasses by slices 
of cork or wood, interposed between the cover and the clip. During 
this process they are kept in the paraffine oven to promote the further 
hardening of the balsam. 
The methods described above are somewhat laborious, but the 
results obtained appear to fully justify the expenditure of effort, as 
photomicrographs are readily obtained showing every detail of 
structure with great fidelity, with a small fraction of the time 
required for the making of drawings. 
In the case of material from which it was desirable to obtain an 
enlarged facsimile of the external features, the following method was 
pursued: The objects were placed in a watch-glass, the bottom of 
which had previously been covered with a smooth coating of black 
wax, flooded with alcohol and illuminated with the concentrated rays 
of a powerful electric lamp. Magnifications of ten or more are 
readily obtained in this way by the use of suitable modern lenses. 
The powerful light allows a stopping down of the aperture of the 
lenses to a sufficient degree to bring about sharpness at all depths 
of focus, without any material loss of brilliancy, in spite of the 
almost black color of the lignites. After the negative is secured, 
the black background, which is necessary for throwing up the sur- 
face details, is readily painted out by one of the numerous spotting 
