91 
NOTE on the STINGING HAIRS of URTICA DIOICA. 
By R. J. Harvey Gipson, M.A., F.LS., 
LECTURER ON BOTANY IN UNIVERSITY COLLEGE, LIVERPOOL, 
AND 
Miss Amy WaArHAM, Student of Biology. 
With Plate I. 
[Read 14th February, 1890. ] 
THE following observations were made by us in the hope 
of determining the nature of the substance in the stinging 
hairs of the genus Urtica. It may be well, by way of 
introduction, to quote the account given by De Bary.* 
‘‘We know of the erect stinging hairs of the Urticacee, Loasez, and other 
plants named above (page 60), which resemble one another so remarkably in 
structure and form, that the brittle point breaks off when touched, and that 
a fluid issues through the hole thus made which causes more or less slight 
inflammation when applied to the human skin, especially if it enters the small 
wounds caused by touching the hair itself. It is further known of this fluid 
that it has, like most cell fluids, an acid reaction, not alkaline as stated 
formerly.+ On the fact that by distilling the nettle plant with sulphuric acid 
formic acid is obtained, the conjecture has been founded that the latter 
substance causes the phenomena of stinging.t But as a matter of fact nothing 
is known of the active substance, not even whether it is to be sought for in 
the acid fluid, or in the protoplasm.” 
De Bary also refers to a paper by Duval-Jouve, which 
he says however ‘‘ gives no new information.§ We know 
of no more recent literature on the subject. 
The structure of the adult stinging hair is too well 
known to need redescription. We may note, however, that 
two forms of hair occur on the nettle leaf, one type being 
* «Comparative Anatomy of Phanerogams and Ferns,” p. 68. 
+ P. de Candolle, ‘‘ Physiologie,” iibers. vy. Roper, vol. i., p. 193. 
£ Von Gorup Besanez, ‘‘Jour. f. Pract. Chemie,” vol. xlviii., p. 181. 
§ ‘‘Bull. Soc. Bot. France,” vol. xiv., p. 36. 
