Populus r ^45 



4 in. long, about 2 in. broad, rounded or occasionally cuneate at the base, contracted 

 at the apex into a long glandular acuminate point ; glabrous on both surfaces, 

 greenish or slightly whitish beneath, but never so plainly white as in the ordinary 

 balsam poplars ; margin non-ciliate, with a very narrow translucent border, only visible 

 with a strong lens, and usually with regular crenate serrations ending in incurved 

 glandular points, occasionally irregular with shallow lobes ; nerves seven to eight 

 pairs, those at the base arising together and making the leaf pseudo-five- to seven- 

 palminerved ; glands at the base of the leaf on the upper surface variable, none, one, 

 or two being present ; petiole variable in length, with scattered pubescence, terete, 

 with the groove on the upper surface well-marked or not apparent. Leaves on short 

 shoots, small, rhombic. 



Staminate catkins, 2J to 3 in. long ; scales pale green with a brownish edge, 

 ending in about fifteen long filaments ; axis glabrous, crowded with flowers ; stamens 

 about sixty, with salmon-red anthers and very short slender white filaments ; 

 disc glabrous, oblique, slightly concave. Pistillate catkins and fruit not seen ; 

 according to Koehne the ovary, fruit, and disc are glabrous. 



This poplar occurs in both sexes, the staminate tree being the one commonly 

 known as P. certinensis, which is a finer tree at Kew than those labelled 

 P. berolinensis, which are probably pistillate, though they have not yet flowered ; the 

 latter differ in the looser longer pubescence of the branchlets. 



This beautiful tree is stated by Koch to have originated in the old Botanic 

 Garden at Berlin, through the pollination of a tree of P. laurifolia by the 

 pollen of either an adjacent black Italian poplar or of a Lombardy poplar. It 

 is a remarkable hybrid, between two species belonging to different sections of the 

 genus (a black poplar and a balsam poplar), and shows intermediate characters, the 

 thin translucent border to the leaf being a character of the black poplar, while the 

 viscid buds and slightly whitish leaves show the influence of the balsam poplar 

 parent. The original tree is no longer living, but dried specimens of it in the 

 Berlin Herbarium show that it was pistillate. The origin of the staminate tree is 

 unknown, but the late Herr Spath informed us that he received it under the name of 

 P. certinensis from Dieck of Zoschen in 1885, and from Transon of Orleans in 1886 ; 

 and, as Dieck's catalogue of 1885 mentions it as "P. certinensis (?) h. Gall." it is 

 likely that it came originally from France. 



There are two fine examples of the staminate tree at Kew, which were obtained 

 from Dieck in 1889 ; these measured, in June 1912, 57 ft. by 3 ft. 5 in. and 50 ft. by 

 2 ft. 8 in. There is also a good specimen, nearly as tall, at Grayswood, near 

 Haslemere ; and another at Glasnevin, about 30 ft. high in 19 13. 



This species was introduced into America by the Arnold Arboretum, and, 

 according to Professor S. B. Green, 1 is perhaps the best poplar for planting on the 

 prairies of the north-west, as it is perfectly hardy in even the most exposed situations, 

 and is rarely if ever affected with leaf rust, which so often checks the growth of the 

 native cottonwood. Its timber is useful for buildings and floors. It grows readily 

 from cuttings, and bears close planting well. (A. H.) 



1 Cf. L. H. Bailey, Cornell Univ. Agric. Exp. Station, Bull. 68, p. 213 (1894). 

 VII 2 C 



