NOTES 
ON LEFTOMIN. — About forty years ago, Schonbein 1 discovered 
that various parts of plants contain substances which give certain re- 
actions with tincture of guaiacum : (i) substances (or a substance) which 
cause the guaiacum to turn blue immediately on contact 5(2) substances 
(or a substance) which only cause the guaiacum to turn blue in the 
presence of hydrogen peroxide. The substances of the first class are 
those which are now generally known as oxydases : but it is not with 
these, but with those of the second class that I am now concerned. 
Schonbein enumerates a number of vegetable substances which 
give the blue reaction with tincture of guaiacum to which hydrogen 
peroxide has been added : such are gluten (from wheat-flour), diastase, 
emulsin, myrosin, yeast, watery extracts of various seeds (barley, oats, 
millet, poppy, cress) and of various roots (Dandelion, Lettuce), as also 
of potatoes. 
Although attention was drawn to this subject by Jamieson 2 in 1878, 
it was not until the recent publication of Raciborski’s observations that 
it came prominently into notice. Raciborski 3 has proved the presence 
of a substance giving this reaction, not only in vegetable liquids, such 
as coco-nut milk and latex, but also in various tissues, such as the 
endodermal passage-cells in the aerial roots of Orchids, the lenticels, 
the spongy parenchyma of aquatic Phanerogams, and more especially 
the sieve-tubes of a number of plants. It is, in fact, to emphasize the 
occurrence of this substance in the phloem that he has given to it 
the name leptomin ; a designation which seems to be misleading, inas- 
much as it suggests that the substance in question is in some special 
way associated with the sieve-tissue, whereas his own researches 
prove that it is widely distributed in the tissues and fluids of plants. 
Raciborski’s suggestion as to the probable physiological significance 
of ‘ leptomin ’ is perhaps even less justifiable than his nomenclature. 
1 Katalytische Wirksamkeit organischer Materien und deren Verbreitung in der 
Pflanzen- und Thierwelt : Journ. f. prakt. Chemie, 89, 1863. 
2 Nature, vol. xviii, 1878. 
3 Ber. d. deutsch. bot. Gesellschaft, xvi, 1898 : Flora, 85, 1898. 
[Annals of Botany, Vol. XV. No. LVII. March, 1901.] 
