the Jerusalem Artichoke ( Helianthus tuber osus). 233 
chymatous tissue, the fibro-vascular tissue being extremely 
reduced. The microscopical tests for inulin are very imper- 
fect, depending on precipitation in particular forms by alcohol 
or glycerine and chiefly on the occurrence of the well- 
known sphaero-crystals. In working at the micro-chemical 
reactions of inulin I was however fortunate in finding a test 
which always indicated it when present and enabled me to 
see exactly where in the sections the cells contained it. This 
was a solution of orcin in alcohol. On warming with strong 
HC1 a section soaked in this reagent, the cells containing 
the inulin were stained a deep orange-red. The commercial 
preparations of inulin which I had gave the reaction in a 
very marked manner, and on treating, in the way described, 
sections in which the sphaero-crystals had been deposited, 
these dissolved leaving an orange-red area which they had 
occupied. 
I found too that solutions of inulin boiled with strong 
HC1, to which a little orcin in alcohol had been added, took 
on this deep orange-red tint. Phloroglucin was as efficacious 
as orcin, the colour being rather more brown. On the tube 
cooling the clear orange-red colour was replaced by a brown 
precipitate. In tracing the progress of the inulin I used the 
orcin-reaction. 
As the young stem grew, the inulin could be seen to follow 
its increase in length, occupying the centre of the shoot, and 
leaving the circumference free. It did not reach so far up- 
wards as the growing-point but stopped abruptly just behind 
the actively growing zone, so far as I could make out. It 
was accompanied in its progress by sugar, which extended 
rather further forwards, but which also could not be detected 
with certainty in the growing-point. This agrees with obser- 
vations which have been made in the cases of growing-points 
supplied with sugar at the expense of starch. From the 
power of dialysing which inulin has been shown to possess, 
this travelling of it towards the growing-point does not seem 
remarkable. Its occurrence just behind the growing cells 
may be due to an actual transit of the stored inulin before 
