200 Parkin.—Observations on 
prepared from it remains indefinitely of a light colour. On the 
other hand, the latex from the wall of the unripe capsule 
(fruit) changes on exposure, from milk-white to black. The 
darkening is wholly prevented, if the latex is quickly sub¬ 
jected to heat. No doubt there is an oxydase present in 
the latex of the capsule. Sometimes, but by no means 
always, the changing latex from the capsule shows an inter¬ 
mediate brick-red colour, before the blackening sets in. A 
peculiarity of this reddish colour is that it disappears on 
heating, whereas the black colour is permanent. The latex 
made to exude from young shoots sometimes blackens, but 
not always, whereas the blackening of the latex from the 
capsule is without exception in my experience. Oxydases, 
as a rule, show their presence more often in young organs 
than in mature ones. 
III. The Carbohydrates of Latex. 
Sugar in variable proportions has been shown to be of frequent 
occurrence in latex. The little—0-3 to 0-7 per cent.—found in 
the trunk-latex of Hevea seems at all times to be cane-sugar. 
Examinations made at different periods of the year, thirteen 
in all, showed no reduction of Fehling’s cupric reagent, till 
after heating with an acid. The latex of Manihot Glaziovii , 
examined on three separate occasions, behaved similarly. 
Tannin is absent from both of these latices. 
May not some of the sugar contained in the collected latex 
come from the surrounding injured tissues, and not be origin¬ 
ally present in the laticiferous tubes? I have noticed that 
in certain species of Ficus , the first two or three drops of 
latex from an incision in the stem taste much sweeter than 
those which exude later. A few experiments regarding this 
point were made on the latex of Hevea. From each incision 
the first latex exuded was collected separately from the next 
and so on. The sugar was then estimated in these different 
portions. Time did not allow of these experiments being 
more thoroughly carried out, but in such as were done the 
