44 
Twenty-first class. 
11. Fr. with a foliaceous, 3-lobed envelope. Hornbeam 
Carpinus. 518. 
— Fr. enclosed in an urceolate, inflated envelope 
Ostrya. 519. 
12 (8). Male catkins almost globular, suspended. Beech 
Fagus. 514. 
— Male catkins cylindric ...... 13 
13. Male catkins erect. Fr. 2—3 in an envelope. Chestnut 
Castanea. 515. 
— Male catkins drooping. Fr. isolated in their envelope 
11 
14. Male catkins dense. Fr.-envelope herbaceous-fleshy, gen. 
enveloping the fr. or entirely enclosing it. Hazel 
Corylus. 517. 
— Male catkins interrupted. Fr.-envelope leathery-ligneous, 
short, cup-shaped, only surrounding the base of the fr. 
Oak .Quercus. 516. 
15 (7). Ls opp., entire, persistent. Box . Buxus. 502. 
— Ls altern., lobed or toothed, falling in autumn . IS 
16. FIs in short spikes; the fern, fls forming a false berry 
like that of the wild mulberry, in consequence of the 
perianth becoming fleshy. Mulberry . Morus. 510. 
— Fls enclosed in a fleshy, pear-shaped, hollow receptacle. 
Fig .Ficus. 511. 
17 (1). Pis composed of small ls (fronds) at most 10 mm 
long, floating freely on the water . Lemna. 535. 
— Pis with stem and ls.. 18 
18. Ls with dichotomous or pinnate divisions . . 19 
— Ls undivided. 20 
19. Seps 10—12. Cor. 0. Stas 12—20. Ls several times 
dichotomous.Ceratophyllum. 192. 
— Cal. 4-partite. Pets 4. Stas 8. Ls pectinate-pinnatifid or 
pinnatipartite.Myriophyllum. 189. 
20. Stas numerous. Ls sagittate . . . Sagittaria. 528. 
21 
Najas. 534. 
22 
— Stas 1—3 
21. Ls with spiny teeth 
— Ls entire 
22. Fls in globular heads 
— Fls not in heads 
23. Ls linear or long-obovate 
— Ls almost capillary 
24 (1). Ls pinnate. Fls in heads. Stas 20 — 30. Stig. brush-like 
Sanguisorba. 176. 
— Ls simple, undiv. or lobed. 23 
25. One pedicelled ovary with 3 styles (fern, fls) and 10—20 
stas (male fls) in a common calyx-like envelope. Pis 
with milky juice and fls in a cyme or umbel 
Euphorbia. 503. 
Sparganium. 537. 
23 
. Callitriche. 191. 
Zannichellia. 533. 
