i8o8 The Trees of Great Britain and Ireland 



Fruiting catkins, 6 to 8 in. long ; capsules 3- to 4-valved ; seed with long white 

 hairs, enclosing the catkins, when the capsules dehisce, in a dense mass of cotton. 

 I. Var. occidentalis, Rydberg, in Mem. New York Bot. Garden, i. 115 (1900). 



Populus occidentalism Britton, ex Rydberg, Fl. Colorado, 91 (1906); Gombocz, in Math. Termes. 



KiJzl. XXX. 79 (191 1). 

 Fopulus Sargentii, Dode, in Mem. Soc. Hist. Nat. Autun, xviii. 40 (1905) 5 Britton, N. Amer. Trees, 



178 (1908). 

 Leaves smaller, deltoid, truncate at the base, abruptly contracted at the apex into 

 a long acuminate point, with few and coarse serrations. 



This is the common black poplar in western North America, east^ of the 

 Rocky Mountains from Saskatchewan and Alberta southwards to New Mexico and 

 western Texas ; and is the characteristic tree on the river flats of the western prairies. 

 p. monilifera is distinguishable from all the hybrids by the dense persistent 

 cilia on the margin of the leaf, the peculiar few hooked serrations, the abrupt 

 cuspidate apex, and the constancy of the glands at the base ; and when flowers are 

 obtainable by the large number of stamens (about sixty), and the shape of the stigmas. 

 It has been confused by most dendrologists with the hybrids, which both on the 

 Continent and in England have entirely supplanted it in cultivation. It has become 

 an extremely rare tree ; and the only specimens which we know of in England are a 

 tree apparently past its prime, though probably not over sixty years old, at Bradwell 

 Grove, Burford (Oxon), the seat of W. H. Fox, Esq., which Elwes measured in 

 1910 and found to be 91 ft. by 9 ft. 3 in. ; and another at Penrice Castle, Glamorgan- 

 shire, about 80 ft. high and 13 ft. 9 in. in girth. The stem of the latter has deeply 

 furrowed bark, and gives off the first branch at twenty-seven feet up ; above are 

 numerous wide-spreading branches. 



An old tree in the Cambridge Botanic Garden was cut down two years ago, 

 but a cutting from it is now making vigorous growth. Elwes has also obtained 

 cuttings from America, which are thriving at Colesborne. 



Distribution of P. Monilifera and P. Angulata 



P. monilifera and P, angulata are considered by modern American botanists 

 and foresters to constitute a single species, which they term P. deltoidea, Marshall, 

 with the following distribution, according to Sargent : — Province of Quebec and the 

 shores of Lake Champlain, through western New England and New York, Penn- 

 sylvania west of the Alleghanies, and the Atlantic states south of the Potomac 

 river to western Florida ; and westwards as var. occidentalis to the base of the Rocky 

 Mountains from southern Alberta to northern New Mexico ; comparatively rare 

 and of smaller size in the east and in the coast region of the south Atlantic states 

 and east Gulf states ; a large and abundant tree along the streams between the 

 Alleghany range and the Rocky Mountains. 



P. monilifera and P. angulata are undoubtedly connected by intermediate forms ; 

 and the view that they constitute one species is possibly true in a wide sense, but 



1 It is reported to occur in Idaho by M. E. Jones, Montana Botany Notes, 24 (19 10). 



