3(2). Pedicels not recurved at fruiting time: submersed dissected leaves (some- 

 times the only kind) usually petioled, the first divisions arising 

 usually but not always well above the non-dilated stipular leaf bases 

 (the ends of these not free), usually collapsing when withdrawn 

 from the water, not circinate, usually about equaling or a little 

 shorter than the internodes; achenes usually about 10 to 20 or as 



many as 40; dissected leaves usually repeatedly trichotomous 



29. R. aquatilis. 



3. Pedicels recurved at the bases at fruiting time; submersed dissected leaves 



(the only kind) usually sessile, the first divisions arising within the 

 usually dilated stipular leaf bases (the ends of these often free), 

 usually not collapsing when withdrawn from the water, circinate, 

 much shorter than the internodes; achenes mostly 30 to 45 or 80; 



dissected leaves usually once- or twice- trichotomous 



30. R. subrigidus. 



4(1). Pericarp striate, the nerves 3 or more on each face (these sometimes 

 branched), the ovary wall thin and usually fragile at fruiting 

 time (5) 



4. Pericarp not striate nor nerved, thick and firm (6) 



5(4). Fruiting receptacle enlarged to several times its size in anthesis, cylindroid 

 or long-ovoid; nectary scale overarching the nectary, truncate, the 

 margins free from the blade of the petal; stolons present; leaves 

 simple 27. R. Cymbalaria. 



5. Fruiting receptacle but slightly enlarged from its size in anthesis; nectary 



scale not overhanging the nectary, consisting of a mere transverse 



ridge below the gland; stolons not present; leaves compound 



28. R. ranunculinus. 



6(4). Leaves {both cauline and basal) entire, dentate, serrulate or wavy; dorso- 

 ventral measurements of the achene not more than twice or thrice 

 the lateral; nectary scale forming a pocket (7) 



6. Leaves (either the cauline or the basal) lobed, parted or divided (very rarely 



all the leaves entire in single plants of R. glaberrimus var. ellipticus) 

 (10) 



7(6). Perennials; achenes 1.2-3.2 mm. long, the beaks 0.3-1.5 mm. long, rarely 

 less; petals 5 to 10, usually large and conspicuous, longer than the 

 sepals (8) 



7. Annuals; achenes 0.6-1 or rarely to 1.5 mm. long, the beaks 0.1-0.2 mm. 



long (9) 



8(7). Achene beak 0.2-0.5 mm. or rarely to 0.7 mm. long, the stigmatic surface 

 mostly across the broad apex of the style 20. R. flaminula. 



8. Achene beak 0.8-1 mm. long, the stigmatic portion long-attenuate 



21. R. hydrocharoides. 



9(7). Petals 5 to 9, large and conspicuous, about twice as long as the sepals; 

 styles in anthesis 0.5 mm. long, filiform, deciduous in fruit; head of 

 achenes hemispheroidal or ovoid 22. R. laxicaulis. 



9. Petals 1 to 3, minute and inconspicuous, shorter than or equal to the sepals; 



styles in anthesis 0.1-0.2 mm. long 23. R. pusillus. 



10(6). Achenes covered with spines, hooks or papillae, or with papillae produced 

 into hooked hairs, rarely smooth in R. Sardous; dorsoventral meas- 

 urement of the achene 3 to 6 times the lateral; receptacle in fruit 

 1 to 3 times its length in anthesis (11) 



10. Achenes smooth, sometimes hairy (13) 



929 



