KEY TO THE FAMILIES 



in cross-section, with many flat seeds: erect 



herbs with 4-angled stems 154. Pedaliaceae 



20b. Ovary inferior. 



27a. Fls. not in heads subtended by involucres. 



28a. Shrubs or woody vines (brs. sometimes herbaceous in 



Sambucus) 163. Caprifoliaceae 



28b. Herbs. 



Stems weak: aquatic herb with solitary axillary fls. and 

 indehiscent 1-seeded fr. bearing 3 recurved hooks at 



the top 



Stems erect or decumbent: terrestrial plants with fls. in 

 cymes, panicles or racemes. 

 Stamens 1-3: fr. 1-seeded: calyx very small infr.: lvs. 



opposite : plants with watery sap 164. 



Stamens 5; the filaments sometimes united: fr. many- 

 seeded: calyx often conspicuous in fr.: lvs. alternate: 



plants with milky juice 168. 



27b. Fls. in heads subtended by involucres: fr. a cypsela. 



Stamens 4, distinct: lvs. opposite, rarely whorled 165. 



Stamens usually 5; the anthers united into a tube surround- 

 ing the style: lvs. mostly alternate, sometimes opposite 

 or whorled 169. Composiiae 



Trapella 



Valeriavaceae 



Lobeliaceae 

 Dipsacaceae 



b. MONOCOTYLEDONEAE 



la. Aquatic or marsh plants, often submersed or floating. 

 2a. Plants in the form of a floating thallus, oblong, ovoid or ellip- 

 soid, without normal stems and lvs 182. Lemnaceae 



2b. Plants with normal stems and usually with foliage lvs. 

 3a. Stems submersed or floating. 



4a. Herbs with slender elongated stems. 

 5a. Lvs. alternate or rarely opposite. 



Fls. clustered or in spikes 172 



Fls. solitary in axils of sheathing leaf-bases 173. 



5b. Lvs. verticillate or in a basal rosette. 



Lvs. verticillate 



Lvs. in basal rosette 



4b. Herbs apparently stemless, or with creeping rootstocks. 



Plants floating: leaves orbicular-cordate, spongy-reticulate. 

 Plants submersed; the crown not floating. 



Lvs. narrow, ribbon-like: perianth single 



Lvs. with winged petioles; blades lanceolate, ovate or 

 cordate, some of them floating: perianth double. .. 

 3b. Stems mostly not submersed. 



6a. Perianth lacking, or of bristles or scales, never petaloid. 

 7a. Fls. not in spikelets, though sometimes in heads. 



8a. Infl. in dense cylindrical spikes: marsh plants of grass- 

 like habit. 

 Spikes terminal, up to 30 cm. long and 3 cm. in diam.170. Typhaceae 

 Spikes lateral, on the sides of a leaf-like scape, 3-6 cm. 



long Acorus 



8b. Infl. in heads, cymes or fascicles. 



Fls. in globular or hemispherical heads. 



19 



Potamogetonaceae 

 Najadaceae 



Hydrilla 

 Eriocaulon 



Hydrocharis 



Vallisneria 



Otlelia 



