NATURAL HISTORY NOTES. 
209 
wliat constricted, 90- 110/x x 20 — 26 g. It will be observed that the 
fungus is very similar to Macrosporiwm Brassiere, Berk., but if it is 
identical, as Saccardo asserts, then the descriptions and figures of the 
latter species must represent the spores as attached by the wrong end. 
The spores of the Alternaria were mostly single, or occasionally two or 
three in a short chain. I shall be glad to know the truth of the 
matter.—W. B. Grove, B.A. 
Formation of Starch.— Professor Sachs has been engaged in the 
study of the rate of formation and disappearance of starch in the 
leaves of growing plants, and as the process for conducting these 
researches, unlike those for determining the amount of absorption of 
water by the living plant, is easy to carry out, and requires little or no 
apparatus, I think I may venture to describe it more in detail, as, 
perhaps, some present, especially those who reside in country districts, 
might be inclined to assist in tliis research by their own observations. 
The leaf to be examined is first plunged into boiling water for about 
ten minutes, then taken out and digested in alcohol for about the same 
time (I find methylated spirit answers perfectly well). This treatment 
extracts the whole of the colouring matter (chlorophyll) and leaves 
the leaf perfectly white. The leaf is now placed in an alcoholic 
solution of iodine, and the presence or absence of starch is demonstrated 
in a few minutes. The absorption of iodine commences at the edges, 
and soon colours the leaf blue-black if much starch be present, or 
brown if the quantity of starch be but small. The venation of the 
leaf appears as a pale network upon a dark ground, rendering it a very 
beautiful object; but all my efforts to preserve the specimen beyond 
a few hours have hitherto failed. The curious and interesting 
information obtained from these researches is, that the amount of 
starch present in the leaf of any given plant varies considerably under 
different circumstances. In direct sunshine, and under otherwise 
favourable circumstances, starch is formed very rapidly; but it 
generally disappears entirely during the night, so that a leaf collected 
in the evening will prove full of starch, while another leaf of the same 
plant collected before sunrise will not show a trace. It is also an 
interesting fact, but one we should quite anticipate, that if the air 
surrounding the plant is deprived of its carbonic acid by means of 
caustic soda, no production of starch takes place, even in direct 
sunshine, and with warmth and moisture that would under other 
conditions be sufficient. Again, the gradual increase in the quantity 
of starch produced during the day, and under specified conditions, is 
a matter of great interest, as it would point to certain times and 
conditions when the plant would probably be more vigorous, and the 
activity of its medicinal principles greater than at some other time. 
We already recognise the importance of plants intended for medicinal 
use being collected at certain periods of growth, but it is possible that 
we have still something to learn upon this subject.—From the 
Pharmaceutical Jonrnal. 
English-grown Medicinal Rhubarb.— At the recent meeting of the 
British Pharmaceutical Conference, as reported in the Pharmaceutical 
Journal, Mr. W. Elborne read a paper on the cultivation of medicinal 
Rhubarb. It would appear that English-grown “Rhubarb,” from 
Rheum officinale, the plant which was first brought to Europe about 
sixteen years ago (Pharrn. Journ. [3], iii., 301), has now taken its place 
side by side in commerce with that from R. rhaponticum, from which 
it may be distinguished upon fracture by the comparatively black 
colour of the veins imbedded in a white parenchymatous tissue. 
