RANUNCULACEAE. 105 



144. BATRACHIUM. Water Buttercup. 



Perennial aquatic herbs with alternate dissected or palmately 

 lobed leaves, the ultimate segments of the submerged leaves 

 filiform; flowers solitary, rather small, white, borne on peduncles 

 opposite the leaves; sepals and petals usually 5; petals oblong or 

 oval, sometimes yellowish at base; stamens several or numerous; 

 akenes compressed, not margined, nearly beakless, transversely 

 wrinkled. 



Batrachium aquatile (L.) Wimm. Water Crowfoot. Stems 5-40 cm. long, 

 slender, growing in water; immersed leaves flaccid, all finely divided into fili- 

 form segments, 8-20 mm. long; floating leaves 1-5, reniform or orbicular, 

 3-5-lobed or parted; petals white, yellow at base, each bearing a naked nec- 

 tariferous pit; akenes thick, transversely wrinkled, the style short; receptacle 

 hairy. Common in ponds. 



Batrachium aquatile caespitosum (DC.) Piper. Terrestrial on muddy 

 banks, rooting at the nodes; leaves somewhat fleshy with broad divisions. 

 Not uncommon, probably only a terrestrial state of B. aquatile. 



Batrachium aquatile pantothrix (Brot.) Piper. All the leaves immersed 

 and divided into capillary segments. Less common than B. aquatile and 

 sometimes growing with it. 



145. RANUNCULUS. Buttercup. 



Annual or perennial herbs; cauline leaves alternate; flowers 

 solitary or corymbed; sepals usually 5, deciduous; petals as 

 many or more, conspicuous or minute, with a nectariferous pit 

 and a scale at the base of the blade; stamens numerous, occa- 

 sionally few; pistils numerous, 1-ovuled; akenes capitate or 

 spicate, generally flattened, each tipped with a minute or an 

 elongated style. 



Plants aquatic or subaquatic; leaves finely dissected 

 when submersed, less so when aerial. 

 Akenes corky-margined; flowers 15-25 mm. broad. R. delphinifolius. 

 Akenes marginless; flowers 7-15 mm. broad. R. purshii. 



Plants terrestrial, but often growing in very wet places; 

 leaves never finely dissected. 

 Akenes thin-walled, the faces nerved; leaves crenate; 



plant spreading by runners. R. cymbalaria. 



Akenes not thin-walled nor nerved. 

 Leaves entire or nearly so. 



Stems creeping, rooting from the nodes. R. flammula. 



Stems erect, not rooting from the nodes. 

 Plants 30-60 cm. high; leaves lanceolate 



or oblong. R. alismaefolius. 



Plants 10-25 cm. high; leaves cordate or 



subcordate. R. populago. 



Leaves or some of them lobed or divided. 



Faces of the akenes scabrous; annuals. R. hebecarpus. 



Faces of the akenes smooth or merely pilose; 

 mostly perennials. 



