1638

ARBORETUM AND FRUT1CETUM.

PART III,

from which it will be impossible entirely to extricate them, till both the maleand female plants of each sort have been cultivated together for a number ofyears in the same garden. Judging from the plants in the London nurseries,and in the arboretums of the Horticultural Society and Messrs. Loddiges, wethink that all the kinds now in actual cultivation in Britain may be includedunder the heads of P^ cilba, P. tremula, P. nigra, and P. balsamifera.

Poplars, from their rapid growth and great bulk, are liable to have theirbranches broken off by the wind; in which case, if care is not taken to protectthe wound from the weather, the water enters, and the trunk soon rots and be-comes the prey t of insects, which in their turn are fed on by birds. The larvae ofa number of moths live on the leaves of the poplars, such as Tortrix populana,.Bombyx populi, Cerura vinula, Smerinthus populi, S. ocellatus (the eyedhawk moth), Anacampsis populella, and a number of others, some of whichwill be noticed under particular species. The larvae of Cossus Ligniperda(see p. 1386.), of fEgeria crabroniformis (see Mag. Nat. Hist., iv. 445.), andof some others,live on the wood. The larva of the puss moth (Cerura vinula)is one of the few caterpillars that are known to have the voluntary power ofcommunicating electricity. An . interesting account of the manner in whichthis was discovered by a naturalist in Selkirkshire, is given in the Magazine ofNatural History, vol. iv. p. 281. The larva of this insect is very common onpoplars and willows in Switzerland , where the pupa often remains two fullyears, before it assumes the perfect state. ( Ibid., viii. 558.) iPopulus gra'caaffords food to this moth, to the poplar hawk moth (Smerinthus populi), tothe kitten moth (Cerura furcula), to the pebble prominent moth (Notodontazfczae), and'to various species of Clostera, (the chocolate-tipped moths), whichfeed exclusively on the poplar and willow. The larva of Smerinthus populi(Mag. Nat. Hist., viii. 629.) is very common both on poplars and willows,and often strips them entirely of their foliage; the moth of this species isseldom seen, as it flies but little, and only during the night. The larva ofSmerinthus ocellatus is common on willows and poplars from July to the endof September, and the fly does not usually appear till the following spring.It is stated of this insect, that a female produced young without having anyconnexion with the male ; from which it would appear that in certain Lepi-doptera a single pairing can render fertile more than one generation, as wellas in the case of the A'phides. (Mag. Nat, Hist., viii. 557.) Trochilium api-forme (the hornet hawk moth) and fEgeria asiliformis feed on the Lombardypoplar , on which the larva may be found in May and June, early in the morn-ing ; the fly almost invariably mounts to the top of the trees soon after sunnse.(Ibid,, p. 555.) The splendid European butterfly (not yet detected in GreatBritain ), Limenitis populi, frequents the aspen. The caterpillar, also, of thefine Camberwell beauty, or, as it used to be called, the poplar butterfly, feedson the poplar. Both poplars and willows, when the trunks begin to decay,are attacked by the jet ant (formica fuliginosa), more especially in France ,and on this insect that very shy bird, the hoopoe chiefly lives. Among thecoleopterous insects, Rhynchltes populi, Chrysoinela populi and C. treniuke,Saperda populnea, and Orchestes populi, one of the flea weevils, feed on theleaves of poplars. Notices of all the preceding insects, and of various otherswhich attack the poplar and the willow, will be found in the Magazine otNatural History, vols. i. to ix. inclusive. Various epiphytical fungi are foundon the poplar, some of them on the leaves, and others oh the bark of thebranches or trunk; such as Sclerdtium ytopiilinum Pea, E rysiphe aduncaLink and E. yjopuli Link, Erineum aureum Pers., t/redo yjopulina rets .,

and U. ovata Straus. Some others will be noticed under particular species,

and the greater part are included among the Cryptogamia of our Encyclo-paedia of Plants, where several of the species are figured.

$ 1. P. a'lba L. The white Poplar, or Abele Tree.

Identification. Lin.' Sp., 1463.; Willd. Sp. PI., 4. p. 802. ; Smith Eng. Bot., t. 1618.; jT’ erp. 243.; Hook. Brit. 11., ed. 2., p. 432.; ATackay FI. Hibern,, pt. 1. p. 254.; Raii Syn., ™ 5Emma, 2486. ; Baub. Hist., 1. p. 2. fig. 360. * o n 303-;

Syiumymes. P. hlba latifolia Lob. lc., 2. p. 193. fig. 1.; Pdpulus No. 1634. Hall. Hist., i*. ( namcP. major Mill. Did., 8. No. 4. j P. nivea Willd. Arb., 227.; P. alba nlvea Mart, Mill.