1844 The Trees of Great Britain and Ireland 



the base of the midrib on the upper surface, pale beneath ; margin glandular-crenate, 

 non-ciliate, with a very narrow translucent border ; petiole terete, grooved above. 

 Leaves on older trees smaller, about 3 in. long and 2^ in. wide, elliptic-rhomboidal, 

 with an acute or a short cuspidate apex. 



III. PopuLUS PETROWSKYANA, Schroeder, ex Dippel, Laubholzkunde, ii. 200 

 (1892). 



Very similar to the last, but with minute pubescence on the branchlets and the 

 petioles. Leaves on vigorous shoots about 5 in. long and 4 in. wide, ovate, cordate 

 at the base, where there are usually one or two glands on the upper surface ; 

 contracted above into a long acuminate apex ; pale beneath ; serrations deeper than 

 in the preceding hybrid. 



Both these hybrid poplars^ originated in the garden of the Imperial Agricultural 

 Institute at Petrowskoje-Rasumowskoje, near Moscow, and were exhibited by 

 Schroeder at the Moscow Exhibition in 1882, with three other hybrid poplars, which 

 do not appear to have been propagated. P. rasumowskyana was reported to have 

 originated from a P. nigra, pollinated by P. suaveolens ; and P. petrowskyana from 

 a P. canadensis^ pollinated by the same species ; but in all probability the balsam 

 poplar concerned was P. laurifolia. 



Both kinds are said by Spath to be vigorous in growth, but apparently are much 

 less known than P. berolinensis, and have only lately been tried at Kew. I have no 

 information concerning the habit of adult trees, and am doubtful as to whether these 

 two hybrids are really distinct, the material which I have examined being very 

 scanty. 



IV. PoPULUS BEROLINENSIS. 



Populus berolinensis, Dippel, Laubholzkunde, ii. 210 (1892); Schneider, Laubholzkunde, i. 11 



(1904). 

 Populus hybrida berolinensis, Koch, in Wochenschr. Gdrtn. Pflanzenkunde, viii. 225 (1865), and 



Dendrologie, ii. pt. i. p. 497 (1872). 

 Populus certinensis, Dieck, Hauptcatalog. Baumschul. Zdzchen (1885). 

 Populus nigra, var. italica x laurifolia, Koehne, Deut. Dendr. 85 (1893). 

 (?) Populus pseudobalsamifera^ Fischer, in Allgemein. Gartenzeit. ix. 402 (184 1), ex Dode, in Mem. 



Soc. Hist. Nat. Autun, xviii. 55 (1905). 



A tree, columnar in habit, with short ascending branches, and bark similar to 

 that of P. serotina. Young branchlets slightly winged, densely pubescent ; older 

 branchlets also pubescent, rounded, yellowish grey. Buds greenish, viscid, sharp- 

 pointed. Leaves (Plate 410, Fig. 29) on long shoots, ovate or ovate-rhombic, 3 to 



1 First mentioned with a brief description as P. rasumovskoe and P. petrovskoe, Schroeder, in Card. Chron. xviii. io8 

 (1882). These ill-spelled names were perhaps misprints for the correct names given above, which appear to have been first 

 published with marks of interrogation by Dieck, Haupt-Catalog Zoschen, 1886, p. 56. 



2 By P. canadensis, possibly P. marilandica is meant and not P. mmilifera. The glands at the base of the leaf confirm 

 the correctness of this parentage. Schneider, Laubholzkunde, i. 11, gives the different opinions that have been advanced 

 concerning these hybrids. He considers P. Rasumowskyana to be a cross between the Lombardy poplar and P. suaveolens. 



3 Fischer describes here a balsam poplar, commonly cultivated in Russia, the earliest in leaf at St. Petersburg, and on 

 that account probably not a native of Russia. There is no specimen of this poplar available for comparison ; and it is 

 doubtful if it is the same as P. berolinensis. In any case the name is invalid, as P. pseudobalsamifera, Fischer, ex Turczaninow. 

 in Bull. Soc. Most. i. loi (1838) is the name given earher to a specimen, collected by Turczaninow near Lake Baikal, which 

 is preserved in the Kew Herbarium, and is P. suaveolens. 



