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line, and not of a vcflR.! inte-.TupUd with v:i1vcs • and in tliis 

 rcfpedt it difTtrs from thjl of luiiir.iil lymphatics. 



According to this writer, tin; proper uir-vtiTcIs are liori- 

 2oiitiil veffels of liirffe diameter, whicli pafs tlirou;rIi tiie 

 bark of trees to the alUurnnm. Malpi jl\i Iihj given a figure 

 of thefe veffcl.i, and Duhamel mentio!:s fine hin-izontal per- 

 forations through the bark, of trees, wiiieh he believes to 

 be peripir;itory or excveton' organs ; and befides tliefe, he 

 takes notice of others, tlv.it are larger, ilunding promincnr 

 in the birch-tree, aild piercing the exterior bark ; which 

 probablv contain air during the living ilatc of the tree. Dr. 

 Darwin i'uppofes, that the horizontal vefTels full mentioned 

 contain air, enclofed in a ihin moill membrane, which may 

 ferve the purpofe of oxygenating the (iuld in the extremities 

 of fome fine arteries of the embryo buds, in a manner fimi- 

 lar to that by which the air at the broad tnd of the egg is 

 thoiiglit to oxygenate the fluids in the termination ot the 

 placental veifels of the embryo chick. 



AIRA, Aifoc of Hippocrates and Theophnilhis, /jiiir- 

 grafs, in Bo.'anv, a gjnus of tlie tr'nuulriii ili{;\-iii,! clais and 

 order, and of the natural order of gnuiiirin or grafies. Its 

 characters are, that the calyx is a two-floivered, two-valved 

 glume ; the valves ovate-lanceolate, acute and equal ; the 

 corolla bivalve, the valves like the former; neitary two- 

 leaved, leallcts acute, gibbous at the bafe ; the ilamiiia have 

 capillary hlaments, ot the length of tlie flower, with oblong 

 anthers, forked at each end ; tlie pillillum is an ovate germ, 

 the ttyles fetaceous fpreading, with pubefccnt itigmas ; no 

 pericarpium ; the feed fabovate, crowned with the corolla. 

 It differs frjm Melica, in having no rudiment of a third 

 between each pair of flofcules, the number of which varies. 

 Martyn enumerates 14, and Gmclin, in his edition of Lin- 

 na:us, 25 fpecies ; fome of which are naked or awnlefs, 

 and others awned. 



Of the former, Martyn fpecifies, l. A. arunii'inacea, 

 or reedy hair-grafs, with oblong panicle, on one fide 

 imbricate, and flat leaves, found in the Levant and in 

 Cochinchina. 2. A. mlnutit, with loofe panicle, almofl 

 level-topped, and very branching ; an annual graf. found in 

 Spain. 3. A..aqiiat!ca, water hair-grafs, with panicle fpread- 

 ing, flowers fmooth, longer than the calyx, and leaves flat. 

 This grafs generally grows in the margins of pools and 

 watery places, running in the water to a contiderable dif- 

 tance, and is known by the purple or bluifh colour of the 

 panicles, and fweet tafte of the flowers : perennial, flowering 

 in May and June. This, fays the author of the Farmer's 

 Diftionary, is the grafs which contributes chiefly to the 

 fweetnefs of Cottenliam cheefe, and the finenefs of Cam- 

 bridge butter. There is a variety of this which grows in 

 dry foils, with the calyces five-flowered, and the flowers 

 very remote from each other. It occurs in fandy lands near 

 Exmouth, about Northfleet in Kent, in Lancafliire, and 

 Yorkfliire. In Dr. Withering's arrangement it is the poa 

 d'ljlans ; and Dr. Stokes fiifpetls the poa rdrofacla of Mr. 

 Curtis to be the fame with this. Gmelin adds to the clafs 

 of the naked airtz ; 4. A. capcnfs, with a ramofe culm, 

 racemous flowers, and hairy corolla. 5. A. korn'igu, with 

 denfe panicle, fmooth calyces, and afcending culm ; the/o// 

 InfJora of fome authors. 6. A. bengaL-nfu, with ereft pa- 

 nicle, three-flowered pedicle?, and petals woolly within ; 

 the arundo bcngalenfis of other writers. 7. A. miliacea, 

 with very numerous panitles, with flofcules in three's, obtufe 

 and dillindl, and fmooth itiiated leaves. 8. A. ic^'ilopfotdes, 

 with flowers turned to one lide, y/ith one valve of the co- 

 rolla ovatcd and acuminated, and the other columnar and 

 obtufe. Dr. Smith (Flor. Brit, vol.i. p. 83.) adds, K.cr'if- 

 /«/■«,. with panicle fpicated, calyces longer than the peduncle, 



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petals acuminattrd and unequal. It grows in high bnrren 

 palhiresand walls ; perennial ; flowering in July and Augud. 

 The awned a'lr^ enumei-ated by Martyn arc as follow : 

 9. A. fuhjpicata, with leaves flat, panicle fpiked, fio'vers 

 awned on the middle ; awn reflex and locie ; found on the 

 mountains of Switzerland, Savoy, Deiunark, and Lap- 

 land ; perennial. 10. A. cttfphofa or turfy hair-grais, >vith 

 leavei flat, panicle fpreading, petals villous, and awned at 

 the bale ; awn tlrail and ihort : growing in moift meadows 

 and woods, peremiial, flowering in June and July, fome- 

 times trailing on the ground to the length of fevend feet:, 

 and the panicle exhibiting a beautiful purple filky appear- 

 ance. Dr. Withering mentions a variety of this with pani- 

 cle viviparous, flowering in October, and found on Higlifuid 

 mountains. This is apt to grow in tufts, and oceanon irre- 

 gularities in the furfaee of meadows. Cows, goats, and 

 Iwine eat it ; but horfes are not fond of it. It is the roughell 

 and coarfell grafs that grows in palhires or meadows; and 

 cattle will not touch it, unlefs compelled bv hunger, it i.s 

 called by the vulgar haflocks, rough-caps, and bull's faces. 

 To get rid of it, the land ihoiild firft be drained, and the 

 tntls of this noxious weed pared ott and burnt ; and tin- 

 aflies they yield will be a good manure. II. K. Jlexuof,;, 

 or waved mountain hair-grafs, with leaves fetaceous, culms 

 almoll naked, panicle fpreading trichotomous, peduncles 

 flexuofe, and awns geniculated ; perennial; flowering in July, 

 and growing in heaths, woods, and barren paliures; eaten 

 by horfes, kine, and Iheep. Dr. Withering fuggcfts, that 

 this is a variety of the A. moiilana, or rather the fame in a 

 more mature ilate. This is a principal grafs on Ijanliead 

 Down, Mendip, &c. and is equally fine and jiutritivc 

 with Iheep's fefcue. It isofdilHcult cultivation. Dr. Smith 

 (Fl. Br. vol.i. p. 85.) mentions two varieties; one with 

 a panicle, lefs ipreading, and peduncles icarcely flexuofe. 

 This is the A. montaiui of Hudfon, Withering, Relhan, 

 and Leers, but not of Linnaeus. The ^.fctacea of Hudfon 

 does not difler from this ; but the A. molilalia of Linnxus is 

 a vei"y different grafs, and has not yet been found in Britain. 

 The other has a culm more leafy, a white panicle, fcarcely 

 flexuofe, and grows in fliady places. 12. A. montana, with 

 leaves fetaceous, panicle narrowed, flowers hairy at the 

 bafe and awned, awn twilled and very long ; fiippoicd to be 

 a variety of the former ; perennial, in July and Augull; a na- 

 tive of high heaths and landy palUires ; eaten with avidity 

 by Iheep. A variety, called ftlacca, with awns twice the 

 length of the florets, is mentioned by Hudfon. 13. A. 

 alphia, with leaves fubulate, panicle denfe, flowers hairy at 

 tlie bafe and awned, awn (hort ; growing on the mountains 

 of Germany, Savoy, and Lapland. 14. A. villoj'ii, with 

 leaves fubulate, panicle long and narrow, flowers fefquial- 

 teral, fliaggy, awned ; awn ilraight and Ihort : found by 

 Thunberg at the Cape of Good Hope. 15. A. cuii.'/i.cns, 

 grey hair-grafs, with leaves fetaceous, culm leafy, the upper 

 one involving the panicle at bottom, like a fpathe ; awns 

 clavated at tlie apex, Ihorter than the calyx ; a native of 

 fandy Ihores, on the coalls of Norfolk and Suffolk, the 

 walls of Balil, and the fandy fields of Germany and Pied- 

 mont ; perennial, flowering in July ; the avrna caiujceiis of 

 Wiggcrs. 16. A., pritcox, early hair-grafs, with leaves fe- 

 taceous, Iheaths angled, flowers panicle-lpikcd, flolcules 

 feffile, naked at the bafe and awned on the back ; found on 

 dry commons, in ditches, on banks of ilreams, and in wet 

 meadows ; perennial, flowering in May and June, ripening 

 its feeds hi June ; and called by Wiggers, nvtiia piifdUi. It 

 has a fweet tafle ; cows are very fond of it ; and it is eaten 

 by horfes and fheep. 17. A., caryoph'ilka, filver hair-grafs, 

 with leaves fetaceous, panicle divaricated, trichotomous, 



flofcules 



