ASCIDIACEA ASH- TREE. 



ASCIDIACEA ( Li nnseus and Lamarck). These 

 small marine animals are enveloped in an immove- 

 able gelatinous, or coriaceous case, more or less 

 rough and contractile, adhering 1 or fixed by the 

 reversed buccal extremity, free and terminated at 

 the other extremity by two indistinct mammillary 

 tubes, each pierced with an orifice, often papillary, and 

 more or less approximated ; the larger and most ele- 

 vated leading into the bronchial cavity, at the bottom 

 of which is placed the mouth, and the other in the 

 common tube at the termination of the intestinal 

 canal, and to that of the other organ?, the reticulated 

 branchiae lining the branchial cavity. 



De Blainville forms of the Ascidiacea his first 

 family of the order HeterobrdncMata, class Acepha- 

 luphora ; he observes, that to understand the rela- 

 tion existing between the animals of this family and 

 the lameUibrmichiiita acephalophora, it is only requisite 

 to compare them with the last genera of that order, 

 which are constantly in a vertical position ; the 

 buccal extremity beneath, and the anal uppermost ; 

 the hard and coriaceous envelope of the ascidia is 

 analogous to that which covers the body, and parti- 

 cularly the tubes of the truncated mya. The two 

 short tubes which terminate il, rmd even the papilla, 

 more or less internal and radiated, sometimes observ- 

 able, are also found in the little bifurcated extremi- 

 ties of the united siphons of the mya and some of 

 its congeners ; the muscular part of the abdominal 

 mass has disappeared, as not being of any more use ; 

 the month is in the same position, but without labial 

 appendices, and the branchiae are, in fact, in the same 

 place as in the last lamellibranchia?, namely, in the 

 tube itself, but their form is quite different. As to 

 the form of the stomach, liver, heart, and even the 

 other organs, it is evident there is a very great ana- 

 logy of structure and of position. 



ASCOMYS. A genus of Rodentia, or gnawing 

 animals, of which there is only one known species. It 

 belongs to the great natural family of rats and mice, 

 and is about the size of the common rat. It has four 

 grinding teeth on each side of both jaws, in the form 

 of compressed prisms, the first double, and all the 

 others single. The incisors in the upper jaw are 

 marked by two furrows in front. There are five toes 

 on all the feet, and the three middle ones in front 

 have very long and crooked claws, flat on their under 

 sides, and well-adapted for digging in the ground. 

 It has large cheek pouches, which give a singularly 

 thickened appearance to the sides of the head and 

 the upper part of the neck ; and on account of these, 

 some authors have called it mus bursarim, or the 

 pouched mouse ; but as the term " pouched," when 

 applied as part of the general description of an ani- 

 mal, usually refers to the existence of a marsupium, 

 or abdominal pouch, in the female, the general use of 

 the word in any other way is exceptionable. This 

 animal is very low on the legs, but it is an expert 

 digger, and lives in very deep burrows. Its haunts 

 are the uninhabited parts of the interior of North 

 America ; and its food is understood to be vege- 

 table. 



ASCYRUM (Linnaeus). A genus containing five 

 species of North American, chiefly green-house, 

 shrubs. Linnasan class, and order Duidcl/phia pcn- 

 tnndria, natural order, Hypcricine<. Generic cha- 

 racter : calyx of four sepals, the interior largest ; 

 corolla four'-petaled ; stamens variously united at the 

 base ; styles three, sometimes only one or two ; 



capsule one-celled, three- valved ; valves bearing the 

 placenta on their margins. 



ASH-TREE. The Frax'ums excelsior. One of 

 our most common and useful trees. Linnaean class 

 arid order Poh/gamia Dicecia ; natural order Oltince. 

 Generic character : flowers polygamous ; calyx four- 

 parted or none ; corolla of four petals, four-parted or 

 not ; stamens short ; anthers ovate, two-celled, open- 

 ing outwards ; stigma almost sitting, divided ; fruit 

 two-celled, compressed, winged at the top, often one- 

 seeded. 



The Ash Tree. 



The ash, from its long standing in Britain, may be 

 considered a native. In favourable soils it grows to a 

 large size before it is rotten at the core ; and its timber 

 stands next in value to the oak. For all kinds of 

 agricultural implements it is preferred ; and for every 

 purpose where pliability and toughness are required it 

 is inestimable. Whether grown for timber or under- 

 wood, no tree answers the purpose of the planter 

 better than the ash. It is, however, injurious to all 

 tmdergrowths ; its numerous roots run near the sur- 

 face, and exhaust the soil so much, that neither corn 

 nor grass prosper under its shade. For this reason 

 thetree is unsuitable for hedge-rowtimber, and should 

 always be, whether intended for timber or coppice, 

 sown or planted by itself. 



Cultivation. The seeds may be sown on fresh mel- 

 low loam, in beds, either in autumn, as soon as they are 

 ripe, or kept in dry sand during winter, and sown in 

 April. Most of the autumn sowed seeds appear in 

 the following summer ; and many seedlings of the 

 spring sowings do not rise till the following spring. 

 After standing twelve months in the seed-bed, the 

 seedlings may be transplanted into nursery rows, 

 twelve inches apart, to gain strength, before being 

 finally put out in plantations. Underwoods may be 

 raised by sowing the seeds on clean, well-prepared 

 ground, like a crop of corn ; by which means they 

 seldom fail to succeed. Ash coppice may be cut 

 every seven years for hoops, hedging stuff, &c. ; and 

 every tenth or twelfth year for hop-poles, hurdles, and 

 other fencing materials. 



