Notes. 
225 
species of Euphorbia glucose is first formed and then starch from 
it, just as can be effected by experiment in many Liliaceae and 
Orchidaceae, and in the Iris, and he suggests that glucose is always 
first produced and then starch from this when the quantity of it in the 
cell exceeds a certain maximum, varying according to the place. He 
did not succeed in making the onion form starch, and says this may 
be due to one of two things, either, 
(1) the necessary strength of glucose was not reached; or 
(2) as he thinks more probable, the chlorophyll-grains of the onion 
have entirely lost the power of forming starch. 
1 have found, however, that starch can not unfrequently be detected in 
the elongated parenchymatous cells bordering on the vascular bundle, 
which, in the green part of the leaf, always contain chlorophyll- 
corpuscles, in fact the layer known as the ‘ leitscheide/ or conducting- 
sheath. 
Thus in a seedling about six-and-a-half inches long, picked at 
2 p.m. on a warm sunny day, this layer contained starch, in small 
quantities, but at once noticeable when treated with dilute iodine 
solution after potash ; it was found through the whole length of the 
leaf right down to the base, where the leaf had already begun to swell 
to form the future succulent leaf-scale. The green leaf of a seedling 
similar to the above, picked at the same time on a cold damp day, 
contained no starch at all. I have very rarely found small quantities 
in the same layer of cells in the green tubular leaf of older onions, 
e.g. the ordinary spring-onion whose largest leaf reaches a diameter of 
about a third of an inch, when the leaf has stood several hours in 
water after being picked. The chance of finding starch diminishes 
therefore as the leaf grows older. It is usually to be found in larger 
or smaller quantity, often in fair-sized grains in the parenchymatous 
cells round the vascular bundles in succulent leaf-scales of all ages, 
as also in the general parenchyma of the stem where the primary root 
and leaves come off. 
In testing for starch, I followed Sachs’ method of warming the 
sections in potash, neutralising with very dilute acetic acid, and then 
mounting in very dilute iodine. If this was carefully done it was seen, 
at any rate on the side of the bundle towards the epidermis, that the 
starch was contained in the chlorophyll-corpuscles. 
As seedlings are evidently more in the habit of forming starch 
than older plants, I thought they perhaps might be induced to make a 
