Genus Polygonum. 237 
well developed. Below the glands the tissue is strongly sclerized and 
pitted. The petiole is pentagonal in outline, the upper side being the 
longest ; the bundles at the upper angles are somewhat smaller than 
the other four (PI. XVI, Fig. 10). 
Polygonum cuspidatum. 
The nectary is oval in form and slightly concave transversely. The 
tissue beneath is strongly thickened and deeply pitted. The petiole is 
of oval-rectangular form with prominent ridges on either side of the upper 
surface. It contains from 8-9 bundles. 
III. Microchemical. 
In all the investigated species it was found that the tissue below the 
gland was rich in a substance which gave a blue reaction with hydrochloric 
and osmic acids. This was especially marked in the stalk cells, whilst the 
gland cells remained unchanged (PI. XVI, Fig. 11). 
Heating sections with Fehling’s solution gave a red precipitate in the 
gland cells only. But previous heating with H 2 S 0 4 and neutralization 
resulted in an instant reduction of the copper, which formed a copious 
precipitate in the epithem tissue between the nectary and the vascular 
bundle. Older non-secreting nectaries showed hardly any precipitate in 
the epithem. Ferric chloride gave a bluish precipitate in the epithem, but 
in the basal cells this was so marked as to render them almost black. 
Fehlings solution reduces the secretion itself without any previous treatment 
with acid. 
The above results suggest the presence of a glucoside in the epithem 
tissue which by its breakdown supplies the glucose secreted from the 
nectary. 
Concentrated sulphuric acid completely dissolves the sections placed in 
it except the cuticle, the gland cells, and the stalk cells. Sulphuric and 
iodine causes a brown coloration which is darkest for the stalk cells. 
Concentrated caustic potash colours the stalk cells yellow, the tint 
becoming brighter on heating ; the gland cells appear unchanged. Thus 
it would appear that the gland cells are cuticularized and the radial walls of 
the stalk cells are strongly suberized. 
IV. Physiological. 
Most of the following experiments were performed upon plants in pots 
under glass. The experiments with saturated air were conducted on all 
species except P. scandens. The other experiments were chiefly carried out 
on P. cuspidatum and P. compactum. 
Washing out young nectaries with water showed that these have the 
power of repeated excretion of fresh sugar, but after a while this ceases. 
