LI.— THE SMALL NETTLE. 
Urtica urens Linne. 
T HE considerable Family Urticace# was at one time so notoriously heterogeneous 
an assemblage as to be termed the “ botanist’s marine-store shop ” ; but the 
separation of Ulmace<e and Morace<? , and the careful grouping of the residue into 
Tribes, has removed this reproach to systematic botany. The Family now comprises 
some forty genera and over 450 species, the majority of which are Tropical. Europe, 
with fifteen species, is the poorest of the continents in variety ; but, as Weddell 
observes, what it loses in this respect is partly compensated for by the multitude of 
individuals, so that there is perhaps no exaggeration in saying that the five or six 
species each of Nettles and Pellitories which swarm around our habitations cover 
nearly as much ground as the numerous species scattered through Equatorial regions. 
Most species of the Family are herbs or undershrubs, though a few, such as the 
formidable Laportea gigas of Australia, reach the dimensions of trees. Their stems 
are often angular, with thin bark with a very tough fibrous inner layer or bast. 
Their juice is generally watery, and the whole plant is often hairy, the hairs being 
either simple or stinging ones. The leaves are stipulate and may be either opposite 
or scattered : the inflorescences are cymose and often “condensed” into capitula, 
with polygamous flowers, i.e. with perfect, staminate, and pistillate forms often on 
one plant ; and the perianth is usually sepaloid, gamophyllous, and polysymmetric. 
The stamens, which equal the perianth-segments in number and are superposed to 
them, are characteristically curled inwards in the bud ; their filaments are usually 
transversely wrinkled and uncoil elastically in flowering, the dorsifixed anthers 
dehiscing longitudinally and inwards with explosive violence. The ovary is one- 
chambered, with one erect uncurved ovule and the brush-like stigma usual among 
wind-pollinated plants : the fruit is an achene ; and the seed has generally an oily 
endosperm. 
The genus Urtica is mostly herbaceous and belongs mainly to Temperate regions. 
It derives its Classical Latin name from uro , I burn, with reference to the stinging 
hairs with which the whole plants are thickly covered, and several of the specific 
names, such as stimulans , urens , and urentissima , have reference to the same character. 
The stings are unicellular, epidermal hairs with a bulb-like base filled with formic acid. 
This poison reservoir is surrounded by other epidermal cells, so that the sting is 
generally borne up in a little papilla ; its walls are strengthened with calcareous 
matter, but at the summit, separated from the calcified portion by an unthickened 
ring, is a minute hook-like knob the wall of which is silicified. On both stems and 
leaves the stinging hairs are slightly inclined upwards, i.e. towards the apex of the 
organ ; so that if it be grasped from below they are merely laid flat, whilst the 
lightest brush against them in the opposite direction breaks off the little knob. This 
breaks with an oblique fracture, so forming a very sharp point, which will penetrate 
