Notes. 
227 
extreme instance of a plant like Euphorbia Lathyris , since, at any rate 
in seedlings, starch occurs under natural conditions in the same 
position as in this plant. Why more copious formation of starch 
cannot be induced under circumstances which succeed in other cases 
is not evident. One of Schimper's alternative explanations, viz. that 
the chlorophyll- corpuscles cannot form starch, must be rejected after 
what has just been described, as some of them evidently can and do 
form starch. It is however quite consistent with the present state of 
our knowledge to say that the chlorophyll-corpuscles of the assimilating 
tissue proper of the green leaves cannot or do not form starch. 
The other alternative, that it is because the solution of glucose in 
the cell-sap is never sufficiently concentrated, seems rather doubtful, 
since, in the first place, from the quantity of glucose contained in the 
leaves the solution is probably at least as concentrated as almost any- 
where in any plant ; and secondly, because in isolated leaves and 
pieces of leaves placed under the various conditions mentioned above, 
as e.g. in highly concentrated glucose solution in a warm moist 
atmosphere, one would imagine the cell-sap to contain a sufficiently 
concentrated solution of glucose, if such were the necessary condition 
for formation of starch. 
We can only say that for some reason or reasons unknown the 
onion almost invariably stores up the excess of carbohydrate formed 
as glucose instead of in the more usual form of starch. The habit of 
forming starch may have been for some purpose abandoned in the 
course of evolution, in which case it is interesting to note that it is in 
the seedlings that we get an intimation of the more general process of 
assimilation in which starch plays so conspicuous a part. 
A. B. RENDLE, Cambridge. 
A MODIFICATION OF PAGAN’S 4 GROWING SLIDE . 5 
— In the Journal of the Quekett Microscopical Club of last year 1 
Mr. Spencer Smithson described an arrangement designed by the Rev. 
A. Pagan for growing on microscopical slides small organisms, such as 
Rotifers, Algae, &c., which live in water and require a frequent change 
of the medium. The results obtained with it were very remarkable ; 
but in the original design the slide had always to be removed from the 
microscope and kept on a specially-constructed stage, and although in 
1 Ser. II. Vol. HI. No. 18. 
