Salicacese. Hydrocharidese. 
855 
528. Populus. Poplar. XXII, 8. 
1. Scales of the catkins ciliate. Stas gen. 8 2 
— Scales of the catkins glabr. Stas 12—30 . . 4 
2. Full-grown Is glabr. on both sides, almost orbicular, 
often broader than long (rarely slightly acute), sinuate- 
angular-dentate, those of the young shoots very different, 
large, oval, acuminate, short-hairy.—Woods ; everywhere. 3 
tremula L. 2020. 
— Ls gray- or white-tomentose underneath . . 3 
3. Ls very white-tomentose underneath, those of the young 
shoots and terminal branches 3- or 5-lobed. Stig. 4-par- 
tite (cross-wise).—Damp woods, shores; here and there, 
probably introduced. 3 . . . . alba L. 2021. 
— Ls gray-tomentose underneath, those of the young shoots 
and terminal branches n o t 1 ob e d. Stig. 8-partite. Scales 
of the catkins more deeply incised than in the last. 
P. canescens Sm., P. alba-tremula?—As the last but 
much rarer. 3 .... hybrida Bieb. 2022. 
4 (1). Young branches corky-angular. Catkins, especially 
the fern., very lax. Ls broad triangular-oval, gen. broader 
at the base, than they are long, shortly ciliate at the 
edges, larger than in P. nigra. P. monilifera Ait.—An 
ornamental tree originally from N.America. 4 
f canadensis Desf. 2023.*) 
— Young branches subcylindric, faintly angled. Catkins 
dense. Ls glabr. at the edges also ... 5 
5. Branches spreading. Ls triangular-oval.—Water-side; 
distrib. 3 . nigra L. 2024. 
— Branches connivent-erect (in such a manner that the 
general outline appears like a long, narrow pyramid), 
— Cultivated in avenues. 3 . . f italica Mbnch. 2025. 
103. Hydrocharidese. 
524. Vallisneria. Vallisneria. XXII, 18. 
1. Rad. ls linear, grass-like, finely denticulate at the top. 
— Stagnant water; T. (Lugano, Agno). 8 spiralis L. 2026. 
525. Hydrocharis. Frogbit. XXII, 17. 
1. Ls orbicular-reniform, long peduncled.—Ditches, ponds, 
rare. V. J. L. Z. 7 . . . . Morsus ranae. 2027. 
526. Elodea. Elodea. Ill, 80. 
1. Ls in whorls of 3—4, linear-lanceolate, finely denti- 
*) An allied species P. angulata Ait., with angular-winged branches 
is common in the lower Rhone-valley: Jaccard. 
