3688

ARBORETUM AND FRUTICETUM.

TART IIP.

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. alba, 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, suclpas Tortrix populana,Pombyx populi, Ceriira 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 Cbssus Ligniperda(see p. 1386.), of iEgeria erabroniformis (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.) Populus grae'caaffords food to this moth, to the poplar hawk moth (Smerinthus populi), tothe kitten moth (Cerura fiircula), to the pebble prominent moth (Notodontaziczac), and to various species of Clostera, (the chocolate-tipped moths), whichfeed exclusively on the poplar and willow. The larva of Smerinthus pdpuli(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-dbptera a single pairing can render fertile more than one generation, as wellas in the case of the A'phides. (Mag. Nat. Hist., viii. 557.) Trochllium «pi-forme (the hornet hawk moth) and JEgeria 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 sunrise.(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, Rhynchites populi, Chrysomela populi and C. tremulte,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 ofNatural History, vols. i. to ix. inclusive. Various epiphytical fungi are foundon the poplar, some of them on the leaves, and others on the bark of thebranches or trunk; such as Sclerotium yiopulinum Pers., Frysiphe aduncaLink and E. populi Link, Erineum aureum Pers., {/redo popiilina Pers.,and U. ovata Straus. Some others will be noticed under particular species;and the greater part are included among the Cryptogamia of cur Encyclo-paedia of Plants, where several of the species are figured.

SI . 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.; Eng. FI., 4.

p. 243.; Hook. Brit. FI., ed. 2., p. 432.; Mackay FI. Hibern., pt 1. p. 254.; Raii Syn., 44&; Ger.

Enum., 1486.; Bauh. Hist., 1. p. 2. tig. 160.

Synonymes, P. &lba latifolia Lob. lc., 2. p. 193. fig. 1.; Fdpulus No. 1634. Ha//. Hist., 2.-p. 303. ;

P. mkjor Mill, Diet., 8. No. 4.; P. nivea Willd. Arb., 227-; P. alba nivea Mart. Mill. The name