136 AMERICAN MIDLAND NATURALIST 



folioli inferior et nervus eius medianus 



glabri vel subglabri 7. R. deserta. 



b. Petioli, petioluli, rachis, nervus folii 

 medianus inferior glanduloso-hispidi, 

 folia subtus pubescentia et resinosa. 



8. R. poetica sp. nov. 



a. Rachis folii numquam vel not assiduo 



spinosa. Foliola subtus dense pubescentia. 



b. Spinae robustae, rectae vel aliquan- 



tulum curvatae. ..9. R. terrens (R. Maximiliani Nees?). 

 b. Spinae graciles, rectae. 



c. Partes plantae variae omnes valde 



confertae 10. R. subnuda. 



c. Partes plantae variae omnino non 



confertae 11. R. naiadwn sp. nov. 



Analytical key. 



A. Infrastipular spines wanting or not prominent. 

 Stems bristly or prickly. 



a. Stems herbaceous and never more than 

 suffrutescent, 1-2 ft. high. 



b. I.eaflets 7-11, obovate, densely pu- 

 bescent beneath, prickles stiff. . . i. R. heliophila Greene, 

 b. Leaflets 7-11, and between them 



1-8 small leaflets 2. A', heliophila var. foliosissima. 



h. Leaflets 5-9, glabrous beneath, except 

 on the midveins and margins, prickles 



soft, almost as bristles 3- ^- Lunellii Greene. 



a. Stems woody shrubs, 2-5 ft. high. 



c. Leaflets 5-9, receptacles 1-1.5 cm. 

 ! in diameter, achenes 4 mm. high. 



d. Sepals entire, or nearly so. . . .4. i?. gratiosa. 

 d. Outer sepals strongly pin- 



natifid 5. R. gratiosa var. didcissima. 



c. Leaflets 7- 11, receptacles 2 cm. 

 in diameter, achenes 6 mm. 



high 6. R. polyamthema sp. nov. 



A. Infrastipular spines present, and larger than 

 the other spines. Stems not bristly, 

 a. Leaf-rachis regularly prickly. 



