gna 
assumes a brown colour, and becomes appa- 
rently covered with a coat of oil. When 
completely dry it resembles glue, and breaks 
like glass. It is insoluble in water, alcohol, 
and other ; but the acids dissolve it, and 
the alkalies precipitate it. It has a strong 
affinity for the colouring matter of vegeta- 
bles, and likewise for resinous substances. 
When kept moist it ferments, and emits a 
very offensive smell ; the vapour blackens 
silver and lead. Its constituent parts are 
oxygen, hydrogen, carbon, and azote. It 
exists, as we have observed, most abun- 
dantly in wheat, but it is found in large 
qhantities in many other plants. It is glu- 
ten that renders wheat so useful in the art 
of bread making. 
GLYCINE, in botany, a genus of the 
Diadelphia Decandria class and order. Na- 
tural order of Papilionaceae, or Leguminoste. 
Essential character : calyx two-lipped ; co- 
rolla the keel turning back the banner at 
the tip. There are twenty-five species. 
GLYOYRRHIZA, in botany, English 
liquorice, a genus of the Diadelphia Decan- 
dria class and order. Natural order of Pa- 
pilionaceae, or Legbminosae. Essential cha- 
racter: calyx two-lipped, upper lip three- 
parted, lower undivided; legume ovate, 
compressed. There are four species. These 
are tall growing perennial, herbaceous 
plants, with the stalks somewhat woody at 
bottom. The stipules are distinct from the 
petiole ; the flowers in a head or spike from 
the axils and at the ends of the branches ; 
seed vessel a legume or pod, smooth, hairy, 
or prickly. 
GLYPH, in sculptnre and architecture, 
denotes any canal or cavity, used as an or- 
nament. 
GLYSTER, or Clyster among physi- 
cians. See Clyster. 
GMELINA, in botany, so called in ho- 
nour of Joh. George Gmelin, professor of 
natural history at St. Petersburgh, after- 
wards of Botany at Tubingen, a genus of 
the Didynamia Angiospermia class and or- 
der. Natural order of Personate. Vitices, 
Jussieu. Essential character : calyx slightly 
four-toothed; corolla four-cleft, bell-shaped; 
anthers two-parted, two-simple ; drupe with 
a two or three-celled nut. There is but 
one species, viz. G. asiatica. 
GNAPHALIUM, in botany, a genus of 
the Syngenesia Polygamia Superflua class 
and order. Natural order of Composite 
Discoideae. Corymbiferae, Jussieu. Essen- 
tial character: calyx imbricate, with the 
marginal scales rounded, scariose, coloured ; 
GNO 
down feathered ; receptacle naked. There 
are sixty-six species : the numerous species 
of this genus are chiefly under shrubs or 
herbs; the leaves are alternately placed, 
generally hoary ; the flowers usually termi- 
nate the stem and branches in globes or 
corymbs. The calyx is permanent with 
yellow or white scales. 
GNAT. See Culex. 
GNEISS, in mineralogy, is composed 
"principally of felspar, quartz, and mica, 
forming plates, laid on each other, and se- 
parated by thin layers of mica. It differs 
from granite by being shistose ; though, like 
that, it sometimes contains shorl and gar- 
net. The beds of gneiss sometimes alter- 
nate with layers of granular limestone, shis- 
tose, hornblende, and porphyry. It is rich 
in ores, almost every metal has been found 
in gneiss rocks, either in veins or beds. 
Mr. Jameson mentions four kinds of gneiss : 
1. That which approaches to the granular 
structure. 2. The waved or undulated. 
3. The common ; and, 4. The thin slaty ; 
and he says the order of their transition is 
also that of their relative antiquity, conse- 
quently the more granular the structure, 
the older the rock ; and, on the contrary, 
the more slaty, the newer it is. In the last 
member of the series is the smallest portion 
of felspar, and largest of mica ; hence its 
texture is more completely slaty than that 
of any of the others. The other extremity 
contains much felspar, and but little mica. 
The common contains a nearly equal quan- 
tity of felspar and quartz. 
GNETUM, in botany, a genus of the 
Monoecia Monadelphia class and order. 
Natural order of Piperitae. Urticse, Jus- 
sieu. Essential character : male, an ament 
with scales; corolla none; filaments one, 
with two anthers : female, an ament with 
scales; corolla none; style with a bifid 
stigma; drupe with one seed. There is 
only one species, viz. G. gnemon, a native 
of the East Indies, where the leaves, male 
catkins and fruits are eaten. 
GNIDIA, in botany, a genus of the Oc- 
tandria Monogynia class and order. Natu- 
ral order of Veprecute. Thymelaeas, Jus- 
sieu. Essential character: calyx funnel- 
form, four-cleft ; petals four, inserted into 
the calyx; seed one, somewhat berried. 
There are eleven species. 
GNOMON, in dialling, the stile, pin, or 
cock of a dial ; which, by its shadow, shows 
the hour ot the day. The gnomon of every 
dial represents the axis of the world. See 
Dial and Dialing. 
