AC A 
where it is common, it is employed for the 
same purposes to which the Althaea, or 
marsh-mallow, and other mucilaginous ve- 
getables are applied among us. In foreign 
countries the cow-parsnip is said to be sub- 
stituted for it, though it possesses very dif- 
ferent properties. The leaves of this species 
of acanthus accidentally growing round a 
basket covered with a tile, gave occasion to 
Callimachus to invent the Corinthian capital 
in architecture. 2. The thistle-leaved acan- 
thus was found by Sparrman at the Cape of 
Good Hope, and has many leaves, proceed- 
ing immediately from the root, resembling 
those of the thistle. 3- The prickly acan- 
thus grows wild in Italy and Provence, and 
flowers from July to September. Its leaves 
are divided into segments, terminated with 
a sh^rp spine, which renders this plant 
troublesome to those who handle it. -i. T he 
acanthus of Dioscorides, as Linnaeus sup- 
poses it to be, grows naturally in the East, 
on Lebanon, fkc. 5. The holly-leaved acan- 
thus is an evergreen shrub, about four feet 
high, and separating into many branches, 
with leaves resembling those of the common 
holly, and bearing white flowers, similar to 
those of the common acanthus, but smaller. 
6, 7, 8, 9. These species, viz. the entire- 
leaved, procumbent, forked, and Cape acan- 
thi, are natives of the Cape of Good Hope. 
10. The Madras acanthus is a native of the 
East Indies, 
The smooth and prickly acanthi are pe- 
rennial plants, and may be propagated either 
by seeds, which should be sown in a light 
dry soil towards the end of March, and left 
to grow, about six inches asunder, till au- 
tumn, when they should be transplanted 
where they are to remain ; or by roots, which 
may be planted either in spring or autumn 
for the third sort; but the others must only 
be removed in the spring, because if they are 
transplanted in autumn, they may be in 
danger of being destroyed by a cold winter. 
These plants take deep root, and when they 
are once established in a garden, they can- 
not be easily eradicated. The 5th and 10th 
species are too tender to thrive out of a 
stove in England, and cannot be propagated, 
except by seeds, which do not ripen in Eu- 
rope. The other sorts must be treated in 
the same manner with Cape plants. 
Acanthus, in architecture, an ornament 
representing the leaves of the herb acan- 
thus, and used in the capitals of the Corin- 
thian and Composite orders. See Archi- 
tecture. 
ACARNA, in botany, a genus belonging 
ACA 
to the Syngenesia iEqualis class and order • 
receptacle chaffy, down feathery: calyx 
imbricate, invested with scales, corol. flos- 
cular. There are seven species. 
ACARUS, the tick or mite, in natural his- 
tory, so called because it is deemed so small 
that it cannot be cut, is a genus of insects be- 
longing to the order of Aptera, in the Lin- 
naean system. Gmelin, in the last edition 
of Linnaeus’s system, has eighty-two species ; 
of which, some are inhabitants of the earth, 
others of water; some live on trees and 
plants, others among stones, and others on 
the bodies of other animals, and even under 
their skin. The generic character is, legs 
eight: eyes two, situated on each side the 
head: feelers two, jointed; egg-shaped. The 
most familiar species are, 1. the A. siro, or 
common cheese-mite, which is a favourite 
subject for microscopic observations. This 
insect is covered with hairs or bristles, which 
resemble in their structure the awns of bar- 
ley, being barbed on each side with nu- 
merous sharp-pointed processes. The mite 
is oviparous: from the eggs proceed the 
young animals, resembling the parents in all 
respects, except in the number of legs, 
which at first amount only to six, the pair 
from the head not making their appearance 
till after casting their first skin. The eggs 
in warm weather hatch in about a week, 
and the young animal may sometimes be 
seen for a day together struggling to get rid 
of its egg-shell. The mite is a very vora- 
cious animal, feasting equally upon animal 
and vegetable substances. It is also ex- 
tremely tenacious of life ; for, upon the au- 
thority of Leewenhoek, though highly dis- 
creditable to his sense of humanity, we are 
assured that a mite lived eleven weeks glued 
to a pin, in order for him to make observa- 
tions on. 2. The A. exulcerans, or itch 
mite, is a species of considerable curiosity, 
on account of the structure of its limbs : it 
is slightly rounded, and of a flattened shape, 
with the thighs of the two upper pair of legs 
extremely thick and short : the two lower 
pair of legs Lave thick thighs proceeding 
from a very slender base, and are extended 
into a long, stout, curved, and sharp-pointed 
bristle. Dr. Bononio, an Italian physician, 
was the fust, who contended that the itch 
was occasioned by this insect, an account of 
which may be found in the Philosophical 
Transactions, No. 283. Dr. Baker is in- 
clined to think that it constitutes the psora, 
a species of itch distinct from others con- 
founded with it. 3. A. autumnalis, or har- 
vest-bug, of a bright red colour, with the 
