344 Marshall Ward. — On a lily -disease. 
sometimes found to stain with methyl-violet after the action 
of the fungus on the tissues for two or three days. 
I have in my possession, and can show, excellent permanent 
preparations of such cultures as have been described, and it 
may not be superfluous to describe briefly how such prepara- 
tions may be put up. 
Owing to the circumstances of the formation of the organs 
of attachment, it is always comparatively easy to secure any 
culture of more than three days old, and if the cover-slip with 
its hanging drop is lifted with forceps, and placed gently on 
the surface of a vessel of hardening reagent, on which it floats 
with the culture downwards, it usually happens that the 
mycelium, etc. is hardened with little or no disturbance. After 
many trials, with all kinds of stains, etc., I find that picro- 
nigrosin gives by far the most satisfactory results : after 24 
hours the most delicate mycelia are beautifully fixed and 
stained, and the hardening may be then completed in absolute 
alcohol. After two or three changes, at intervals of a day, the 
alcohol has removed all the picric acid, but the specimen is 
stained steel-blue in various shades, and is so thoroughly 
hardened, that it may be passed through oil of cloves and 
xylol, and finally mounted in Canada balsam, without collapse. 
When I state that I have thus mounted mycelia, showing the 
extruded ‘ ferment-drops ’ fixed and stained, it will readily be 
seen that the process is as satisfactory as it is delicate. I have 
also thus fixed and mounted cultures such as those described 
on p. 354, showing the hyphae in situ in the substance of the 
cell-walls (Figs. 55, 56). 
If picric acid alone is used, the hardening may be accom- 
plished similarly, and the preparations (after being washed 
with absolute alcohol) stained with carmine, methyl-violet, 
aniline blue, etc. ; after careful and prolonged washing to re- 
move every trace of acid, beautiful haematoxylin preparations 
may also be made. Such specimens may be so well prepared as 
to preserve the vacuolation in the hyphae : I have not been 
satisfied that nuclei exist in the hyphae. Some of the dyes 
bring out very clearly the zone of mucilage round the organs 
