24 



on an average 1000 pounds of sugar. The United 

 States are said to produce ten million pounds per 

 annum of maple sugar. 



It is the old butts of this tree which yield the 

 beautiful veneers called bird's-eye maple ; but to pro- 

 cure this in its finest shadings of the grain, much_skill 

 is required in cutting it up. 



The ash-leaved maple, A. negundo, was formerly 

 ranked in the Acer family ; but has been separated by 

 Moench, a German botanist, and now made a genus 

 of itself under the generic title of Negundo, and of 

 which there are two species ; viz., N. fraxmifoliam, and 

 N. cri. -spurn. 



The generic character of the order is Flowers 

 polygamous ; calyx five-cleft ; corolla five-petaled, 

 spreading, or none ; germens two or three superior ; 

 seed single, roundish, its capsule terminated by a wing. 



ACETABULARIA (Lamouroux). A genus 

 of umbel-shaped polypidoms or corallines ; the stem 

 branchless, slender, fistnlar, and terminated by a 

 striated radiated umbel, either flat or slightly funnel- 

 shaped. 



The Acetabulariae partake of the characters of the 

 Tubularia3 and Sertulariap, by the situation of their 

 polypi, each being placed in a distinct tube, and parti- 

 cipating in a common existence by means of the stem, 

 to which the lower part of each animalcule is attached ; 

 these tubes, which are very visible and projecting in 

 the lower part of the umbel, blend and disappear when 

 they reach the stem ; they form distinct lines on the 

 upper part of the disk. 



They are found in thick tufts on rocks and solid 

 marine substances ; in the first stage of their develop- 

 ment, the tube attains its full size, and the umbel is 

 extremely small in diameter ; by slow degrees this en- 

 larges and acquires its full size ; when it has attained 

 that point it merely increases in solidity, and soon 

 after perishes ; many circumstances inducing a belief 

 that these polypidoms have but a short existence. In 

 the sea the stems are flexible, gelatinous, and of a 

 greenish colour, the disks occasionally displaying a 

 very brilliant shade of green ; some of these charac- 

 teristics disappear by desiccation, and the polypidom 

 becomes nearly white and very fragile. 



They are found in the tropical and temperate seas 

 of both hemispheres, seldom attaining more than four 

 inches in height. Two species are described by La- 

 mouroux, one of which is found in great numbers in 

 the Mediterranean, and the other in the Antilles. 



ACHATINA (Lamarck ; Bulla, Linnaeus). A 

 class of molusca belonging to the Paraccphnlojrfiora 

 of Blainville. 



The animal inhabiting this shell resembles that of 

 the Helix, though modern naturalists have very pro- 

 perly separated this elegant genus from those of Helix 

 and Buna, with which they were confounded by the 

 Linnaean school. They are an elegant and numerous 

 family of shells, in many respects resembling those of 

 the genus Bulinm; but on examination the distinction 

 is manifest. The columella is smooth and truncated, 

 and the margin of the aperture never thickened, which 

 seems to indicate that the animal breathes only air j and 

 though not altogether incapable of existing in an aque- 

 ous element, probably derives its sustenance from the 

 vegetation on the banks of rivers or stagnant pools, 

 only occasionally venturing into the water from neces- 

 sity rather than habit. The shell is oval or oblong, 

 ventricose, striated longitudinally ; aperture ovate, 

 never thickened or reflected; a smooth straight co- 



A C E T A B U L A R I A- A C H I L L E A. 



lumcllu, truncated at the base, without an opercu'.um. 

 They are oviparous; and one species, the Arhatinn 

 zebra, produces a hard-shelled riru, as large as that ol 

 a small bird. Many species arc clothed with an epi- 

 dermis. 



A. zebra. Fig. 1. 



A. virginea. Fig. 2. 



This genus is subdivided into four specie?. The 1 st, oval 

 and subventricul,/!. zebra, fig. 1. The 2nd species, with 

 the aperture nearly round, rather short, and an internal 

 transverse callosity, A. virginea. The 3rd species, sub- 

 turriculated, and with the last whirl attenuated in front, 

 A. glans. The 4th species, distinctly tr.rriculated, A. 

 col\tmnans.fig.% This last is a reverse or heterostrophe 

 shell, as are some others of the genus. These shells 

 sometimes attain a very great size, and their inhabitants 

 are said to be voracious eaters ; all 

 of.them are properly terrestrial shells, 

 and Lamarck enumerates nineteen 

 species. None have ever been found 

 in a fossil state. Their trivial name 

 is Agate Snaifs; only two of the 

 species are European. The others 

 inhabit the warm countries of the 

 two continents, and Africa abounds 

 in some of the larger species. The 

 internal structure of this, genus is 

 here represented in a sectional point 

 of view. 



ACHILLEA, or YARROW. A natural genus 

 of herbs, belonging to class the Syngenesia, order Poly- 

 gamia snpcrflua, of Linnaeus ; and to the natural family 

 Composites, order Corymbifcrcp, of various authors. The 

 name is derived from Achilles, the pupil of Chiron, 

 who is said to have first used some of the species 

 medicinally. There are about eighty known species, 

 some of which are indigenous in Britain. They are 

 bitter, aromatic, and more or less tonic and stimu- 

 lating. The Aehillea mille/blium, milfoil or common 

 yarrow, is abundant in Britain ; and was formerly used 

 in medicine, but it is now almost neglected. The 

 Highlanders, however, still make an ointment of it, 

 which they use for healing wounds. The Achillrn 

 ptarmica, or sneeze wort, was used to promote sneez- 

 ing, and to increase the flow of saliva. Its roots were 

 reckoned a substitute for the pellitory of Spain, and 



