POPULUS 209 



POPULUS. POPLAR. SALICACE.E. 



A group of large, usually quick-growing, deciduous trees, with alternate 

 leaves pinnately veined or three-nerved at the base, those on vigorous 

 leading shoots larger, and often different in shape and character from 

 those on lateral twigs. Flowers produced in catkins on the naked shoots 

 in spring, the sexes nearly always on separate trees. Male catkins more 

 densely flowered than the female, the flowers composed of usually 

 numerous stamens attached to a disk, and springing from the axil of 

 a toothed or fringed scale, which soon falls away. Anthers red or 

 purple. Female catkins lengthening until mature, the egg-shaped or 

 rounded ovary seated in a cuplike disk, and crowned by two to four 

 stigmas. The seed is surrounded by a conspicuous tuft of white, cottony 

 hairs which enables it to be carried long distances by wind. Poplars 

 occur in most parts of the northern hemisphere, from subarctic regions 

 to subtropical ones, some inhabiting arid places, others always found in 

 association with moisture. 



There are four well-marked groups of poplars : 



I. BALSAM POPLARS. These burst into leaf the first, and are dis- 

 tinguished' by very gummy winter leaf-buds and leaves, which emit a 

 pleasant balsamic odour, especially when just expanding in spring. 

 Leaves usually whitish, but not woolly beneath ; leaf-stalk not compressed. 

 This group includes angustifolia, balsamifera, candicans, laurifolia, 

 Simoni, suaveolens, trichocarpa, tristis. Most of these can be increased 

 by cuttings of leafless shoots in the open ground or by suckers. 



II. WHITE POPLARS. Leaves woolly, and white or grey beneath, 

 coarsely toothed or lobed, the younger trunks and main branches at 

 first pale and smooth, then pitted with numerous diamond-shaped holes. 

 It includes alba and canescens. Increased by leafless cuttings in the 

 open ground. 



III. ASPENS. Leaves with long, laterally flattened stalks, and noted 

 for their restless movement. It includes grandidentata^ tremula, tremu- 

 loides, none of which root readily from branch cuttings. 



IV. BLACK POPLARS. The latest group to break into leaf. Leaves 

 green on both sides and with compressed, slender stalks, nearly always 

 in motion ; margins cartilaginous. Trunks with a corrugated bark like 

 an oak. This group includes angulata, Eugenei, Fremdntii, marilandica, 

 monilifera, nigra, regenerata, robusta, serotina^ Wislizeni. All the black 

 poplars except some forms of angulata are easily increased by cuttings 

 of leafless shoots i ft. or more long, placed in the open ground in 

 November. Many of the male black poplars in spring are handsome 

 on account of their richly coloured catkins. 



The production of hybrids on the Continent, where the poplars seed 

 freely, has produced much confusion in the nomenclature of the black 

 poplar group. Students are much indebted to Prof. A. Henry for a 

 laborious investigation into the tangled identity of these hybrids, the 

 results of which have been recently published. Several hybrids of the 

 balsam poplar group are not of sufficient importance or merit to be given 



