92 LIVERPOOL BIOLOGICAL SOCIETY. 
usually curved and simply pointed, whilst the other is 
nearly straight, considerably larger, has a swollen base, 
and exhibits the familiar bulb-like head. We figure the 
two varieties on Plate I. (figs. 1, 2, 3), and also the apex 
of the bulbous form under a high power in fig. 4. In 
addition to these, small glandular hairs occur consisting 
of a unicellular pedicel and a head composed of two, four 
or eight cells. 
The basal part of the stinging hair forms a pedicel and 
is multicellular, the apical portion of which forms a cup 
supporting the stinging cell proper. The base of the 
stinging cell always shows the presence of abundant 
eranular nucleated protoplasm, which is continued up the 
slightly tapering body of the hair to the extreme apex. 
Sap vacuoles occur in the base and body, but not in the 
apical region of the latter, nor in the bulbous head which 
is always filled with granular matter giving the reactions 
of protoplasm. 
The epidermis at the base of the hair-pedicel gives with 
blue litmus a red reaction and with Congo-red a blue 
reaction, indicating the presence of a free acid. The hair 
itself in many cases does so also, but not by any means in 
all. The reaction when observed was confined to the base 
and body of the hair. It is by no means easy to detect 
the presence of any particular organic acid, especially one 
of a closely related series, in quantities so minute as those 
available in the nettle hairs. 
In order that the following results may be as far as 
possible free from error, we have submitted them to the 
criticism of Dr. C. A. Kohn, Demonstrator of Organic 
Chemistry in University College, whose kind assistance in 
our work we gratefully acknowledge. 
The rough method of distilling the leaves with sulphuric 
acid we rejected as liable to lead to fallacious results. We 
