Ord. 6.] MONOECIA POLYANDRIA. 191 



Ditches and pools. If . 7, 8. Leaves under water, pectinated. 

 Spikes above the surface. 

 2. M. verticUldtum, 4. 218. (Whorled W.) Flowers all axillary. 

 Ponds, less freq. If. 7. Floivering branches above water, all over 

 leafy. 



439. SAGITTARIA. Arrow-head. 



1. S. sagittifolia,2.84:. (Common A.) Leaves arrow-shaped, acute. 

 Ditches. If . 7, 8. Branches of the scape whorled. Fl. white, 

 violet at the base. 



440. ARUM. Cuckow-pint. 



I. A. maculatum, 19. 1298. (Common C, Wake Robin.) Stem 

 none. Leaves halberd-shaped, entire. Common stalk of the 

 flowers club-shaped, obtuse. 

 Groves and hedges. If.. 5. L. shining, spotted. Berry scarlet. 



441. POTERIUM. Salad-Burnet. 



[. P. Sanguisorba, 12. 860. (Common S.) Thorns none. Stem 

 somewhat angular. 

 Chalky hills. If. 7. L. impari-pinnate. Leafi. roundish, serrate. 



442. QUeRCUS. Oak. 



.. Q. Robur, 19. 1342. (Common British O.) Leaves deciduous, 

 oblong ; wider towards the extremity ; their sinuses rather acute ; 

 lobes obtuse. Fruit-stalks elongated. 

 Woods and hedges. Tj . 4. Handsome tree. Wood hard, very 

 valuable. 

 :. Q. sessiliflora, 26. 1845. (Sessile-fruited O.) Leaves on elon- 

 gated stalks, deciduous, oblong ; with opposite, acute sinuses. 

 Woods. T? . 4, 5. Wood less valuable. L. sometimes downy. 



443. FaGUS. Beech and Chestnut. 



. F. Castanea, 13. 886. (Sweet C.) Leaves lanceolate, sharply 

 serrated ; smooth beneath. Prickles of the outer calyx com- 

 pound and entangled. Stigmas six. — Castanea vesca, Br. Fl. 

 Woods. Tj . 5. Introduced ? Large tree. Seeds large, esculent. 

 . F. sylvatica, 26. 1846. (Common B.) Leaves ovate, obsoletely 

 serrated. Prickles of the outer calyx simple. Stigmas three. 

 Chalky hills. Native ? Tjj . 4, 5. Branches spreading. Bark smooth. 

 Seeds triquetrous. 



444. BETULA. Birch. 



B. alba, 31. 2198. (Common B., /3, Weeping B.) Leaves ovate, 

 acute, somewhat deltoid, unequally serrated, nearly smooth. 



Sandy woods. T? . 4, 5. Bark white, papery. Branches slender. 



B. nana, 33. 2326. (Dwarf B.) Leaves orbicular, crenate ; reti- 

 culated with veins beneath. 



Mount, moors, Scotl. Tj . 5. 1 — 2/. much branched, erect. 



