ACA 



ACA 



thistle-leaved acanthus was found by 

 Sp:irnu:in at the C;ip<- of (lood Hr.pe. and 

 has many leave.;, proceeding 1 immediately 

 from the rout, n-s-mbling those of the 

 thistle, .v The prickly u -ws 



wild in Italy :tnd l'ro\ence, and flowers 

 from .li.lv to September. I f s k-a\cs are 

 divided into segments, terminated with ;i 

 sharp spine, which renders this plant t roii - 

 blesonie to those xvho handle it. 4. The 

 acanthus of Dioscoridi-s, as Linnaeus sup- 

 poses it to be, grows naturally in the Ea>'. 

 on Lehanon, &c. 5. The holly-leaved 

 acanthus is an evergreen shrub, about 

 bar feet high, MM! 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, vi/c. the entire -leaved, procum- 

 bent, forked, and Cape acanthi, are na- 

 tives of the Cape of Good Hope. 10. The 

 ,-as acanthus is a native of the East 

 Indies. 



The smooth and prickly acanthi are pe- 

 rennial plants, and may be propagated ei- 

 ther by seeds, which should be sown in a 

 lig-ht dry soil towards the end of March, 

 and left to grow, about six inches asunder, 

 till autumn, when they should be trans- 

 planted 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 au- 

 tumn, they may be in danger of being de- 

 stroyed by a cold winter. These plants 

 take deep root, and when they are once 

 established in a garden, they cannot be 

 easily eradicated. The 5th and 10th spe- 

 cies are too tender to thrive out of a stove 

 in England, and cannot be propagated, 

 except by seeds, which do not ripen in 

 Europe. The other sorts must he treat- 

 ed in the same manner with Cape plants. 



A i \\THI-S, in architecture, an orna- 

 ment representing the leaves of the herb 

 acanthus, and used in the capitals of the 

 Corinthian and Composite orders. See 



\HCIIITKCTI 'UK. 



ACAKNA, in botany, a genus belong- 

 ing to the Syngenesia /Kqualis class and 

 order : receptacle chafl'y, down feath 

 calyx imbricate, limited with scales, en- 

 rol, floscular. There are seven species. 



AC AW US, the tick or mite, in n 

 histon, so called, because it is deemed M> 

 small that it cannot be ci:t, Is a i^i mis of 

 insects belonging to the order ot Aptcra, 

 in tlie Ijmucan system, (imelin, in the 

 last edition of Linnxus's s\ stein, has 

 eighty -two species ; of which, some are 



inhabitants of the earth, others of water ; 

 some live on tries and p!. 

 among stones, and others on the 



ruler thf ir 



skn>. The generic, char::- -eigh', 



ey-s t\. on each side the heud 



feelers two, jointed; egg-shaped. The 

 most familiar species are, 1. the A. siro, 

 or common cheese-mite, which is a fa- 

 vourite subject for microscopic o ; 

 tions. This insect is covered with hair* 

 or bristles, which resemble in their struc- 

 ture the awns of barley, being barbed on 

 each side with numerous sharp-pointed 

 processes. The mite is oviparous : from 

 the eggs proceed the young animals, re- 

 sembling the parents in all respects, ex- 

 cept in the number of legs, which at firs'. 

 amount only to six, the pair from the head 

 not making their appearance till after 

 casting their first skin. The eggs in warn i 

 weather hatch in about a week, and thr 

 young animal may sometimes be seen for 

 a day together struggling to get rid of its 

 egg-shell. The mite is a very voracious 

 animal, feasting equally upon animal and 

 vegetable substances. It is also extremely 

 tenacious of life ; for, upon the ; \,thorit\ 

 of Leewenhoek, though highly discredi- 

 table to his sense of humanity, we are as- 

 sured that a mite lived eleven weeks glued 

 to a pin, in order for him to make observe 

 tions on. 2. The A. exculcerans, 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 Tower pair of legs have thick 

 thighs, proceeding from a very slender 

 .rid are extended into along, stout, 

 curved, and sharp-pointed bristle. Dr. 

 Bononio, an Italian physician, was the 

 first who contended that the itch was oc- 

 casioned by this 'iisect, an account of 

 which maybe found in the Philosophical 

 -283. Dr. Baker is in- 

 clined to think that it constitutes the pso- 

 ra, a species of itch distinct from others 

 confounded with it. 3. A. autumn 



!nu;\ of a bvight red colour, with 

 the abdonu 

 numerous white b 

 to the skin, and is with difficult} 

 gaged. On the part whrre it fixes, i; 

 causes a tumour, about the size of a- small 

 bead, accompanied by a severe itching. 

 The tick\sof this species, which is to be 

 found on dogs and other animals. Mam 

 oftheacari attach themselves to insects 

 of a larger kind, and hence they take their 

 names, as A. coleopterous, found on the 



