Notes . 
95 
parallel to the cut. Leaflets in G~M } cut in various ways, all possessed 
starch in a band of cells bounding and running parallel to the cut. 
In G~M the band was broader than in F. Elsewhere there was no 
starch excepting a small amount coating the vascular bundles for 
a short distance as they radiated from the cuts. 
These results prove that in Oxalis a dilute solution of acid potassic 
oxalate in the assimilating cells will prevent the starch from being 
changed into sugar. Yet during the normal life of this Oxalis there 
is a large amount of the oxalate, still no such accumulation of starch 
ensues. For the explanation of the mystery we must look to the 
distribution of the acid oxalate in the normal leaves of Oxalis. 
Giessler (4) showed that the soluble oxalate is stored in the epidermis 
of the leaf, not in the assimilating tissue. The oxalate is stored in 
the epidermis because its presence in the mesophyll would derange 
the metabolic processes; and not because the plant needs to protect 
itself against snails, &c., as Giessler suggests. The protective 
significance of the superficial distribution of the oxalate is at most 
secondary. 
To sum up : — 
(1) Acid potassic oxalate retards the action of diastase on starch. 
(2) In the living plant the first, and, at the commencement, the 
only visible effect of acid potassic oxalate on the assimilating organs 
is the accumulation of starch, owing to an arrest of the change of the 
starch into sugar. 
(3) The second effect, as the soluble oxalate accumulates, is 
a retardation of the manufacture of starch, and hence probably of the 
assimilation of carbon. 
(4) The last effect, with increased accumulation of the oxalate, is 
the death of the protoplasm. 
These researches therefore confirm the discovery made by Schimper, 
that the evil effects of a lack of calcium are to be attributed to the 
accumulation of acid potassic oxalate in plants which normally contain 
calcic oxalate. They may be regarded as complementary in showing 
that, in the absence of calcium, there is a stoppage of the conduction 
of those carbohydrates only which have entered into the condition of 
starch. Schimper (5) showed that part of the carbon assimilated by 
a plant never enters into the starch-condition, and this has been 
confirmed by Brown and Morris (6). It is therefore clear why growth 
is not at once arrested in shoots or seedlings deprived of calcium. 
