Current Literature 311 



The glabrous form of the European Black poplar (P. nigra 

 var. typica) is confined to southern and southeastern Europe and 

 is rarely cultivated in Great Britain. Its fastigiate form, the 

 Lombardy poplar, (var. italica) is a well known tree, and is 

 probably of sport origin. As is known, most Lombardy pop- 

 lars are staminate, but Henry instances a pistillate tree at Kew. 

 He considers the pistillate trees reported in Germany to be of 

 hybrid origin. 



The other variety, P. nigra var. betulifolia, differs from the 

 typical form in the presence of dense short pubescence on the 

 twigs. It is native to France and southern England, and has been 

 slightly introduced on this continent. The corresponding fas- 

 tigiate form of the pubescent variety is known as var. plantieretisis. 



The North American Black poplar differs from the Euro- 

 pean in the shape of its leaf, its ciliated margin and the pres- 

 ence of glands on the base of the blade in front, as well as by 

 floral characters. Henry distinguishes three geographical varie- 

 ties — var. nionilifera of the northeast, var. occidentalis of the 

 western plains, and var. missouriensis of the southeast. 



The Black poplars cultivated for timber in England, France 

 and Belgium are almost invariably of hybrid origin between 

 the above American and European forms. These are chosen 

 largely on account of their exceptional vigor. Eight of the prin- 

 cipal hybrids are discussed, with distinguishing botanical char- 

 acters, elucidation of their origin, and very interesting figures 

 of size and rate of growth. He instances one 150 feet in height 

 and over 8 feet d.b.h. at 81 years. 



Until lately all the hybrids in cultivation had originated as 

 chance seedlings. But the artificial production of fast-growing 

 hybrids is now receiving attention. We have already noted Prof. 

 Henry's own experiments in this direction in Forestry Quar- 

 terly, vol. XIII, p. 97. 



The article concludes with a key to the above mentioned pop- 

 lars reproduced from The Trees of Great Britain and Ireland, 

 with two plates. This is very useful, as this expensive set is 

 not widely available. 



J. H. W. 



