196 BORAGINACEAE 



Inflorescence a broad, open, round-topped thyrsus; branches usually 

 again branched. 

 Plant tall, 2 dm. high or more; nutlets with acute backs and 

 sharply acute margins; tubercles united into more or 

 less distinct cross-ridges; biennials, with taproots. 

 Nutlets ^ving-margined, with the strong, rather regular cross- 

 ridges luiiting on the back. 11. O. virginensis. 

 Nutlets merely acute-angled, weakly Irregularly cross-ridged. 



12. O. thyrsiftora. 

 Plant low, cespitose perennials, 1-2 dm. high; nutlets with 

 roiinded backs; murications united into star-shaped tuber- 

 cles. 13. O. aperta. 

 Inflorescence, at least in flowers, narrow, almost spike-like, if more 

 open, the branches simple. 

 Plants green, very hispid, only the basal leaves canescent; 

 bristles with conspicuous pvistulate bases, much longer 

 than the short strigose or tomentose pubescence. 

 Leaves linear or narrowly linear-lanceolate; plant 1-2 dm. 



high, very slender. 14. O. Maconnii. 



Leaves, at least the basal ones, broadly oblanceoiate or 

 spatulate. 

 Corolla 7-10 mm. broad; nutlets ovate, more than half 

 as broad as long. 

 Leaves obtuse; inflorescence dense. 



Basal leaves broadly spatulate, usually canescent; 



stem 1-3 dm. high. 15. O. glomerata. 



Basal leaves oblanceoiate, greener; stem usually 

 3-4 dm. liigh. 16. O. aJTmis. 



Leaves acute, strongly hirsute-ciliate; inflorescence 

 not very dense 17. O. spiculifera. 



Corolla 5-7 mm. broad; nutlets lanceolate, less than 

 half as broad as long; basal leaves oblanceoiate, some- 

 what canescent; plant 1-3 dm. liigh. 



18. O. perennis. 

 Plant canescent; at least the basal leaves witli inconspicuous 

 bristles scarcely longer than the other i)ubescence. 

 Plant stout, 2— t dm. high, rather simple; corolla 7-10 mm. 



broad. 19. O. argentea. 



Plant low, less than 2 dm. high, densely cespitose. 



Basal leaves narrowly linear-oblanceolate, glossy, closely 

 appressed-canescent ; nutlets mammillate-papiUose. 



20. O. cana. 

 Basal leaves spatulate, white or yellow, scarcely glossy, 

 at least when matiu-e. 

 Nutlets 1 or 2, acuminate with a blunt apex; calyx- 

 lobes ILnear-subulate. 21. O. nana. 

 Nutlets 4, merely acute; calyx-lobes lanceolate. 



Nutlets more or less rugulose; tubercles more or 

 less confluent. 

 Inflorescence in fruit rather open; corolla-tube 



slightly e.xserted. 22. O. cchinnides. 



Inflorescence congested; corolla-tube not ex- 

 serted. 

 Corolla 7-9 mm. broad. 



23. O. sericea. 

 Corolla 4-6 ram. broad. 



Leaves tomentose and hispid; nutlets 

 tuberculose-rugulose. 



24. O. deprcssa. 

 Leaves strigillose and liispid; nutlets 



sinuately and finely rugulose. 



25. O. caespitosa. 

 Nutlets muricate. 



Inflorescence narrow; plant not more than 1 

 dm. high. 

 Leaves strigillose and hispid. 



26. O. Shant:ii. 

 Leaves subtomentose and liispid. 



27. O. dolosa. 

 Inflorescence open; plant 1-2 dm. high. 



28. O. comniixla. 

 Nutlets smooth. 29. O. salmonensis. 



Corolla-tube long-exserted ; cespitose perennial, rarely biennial. 

 Corolla white. 

 Nutlets rough. 



Nutlets more or less distinctly rugose, with irregular cross-ridges, as well as 

 muricate. . 



Fruit depressed-globose; nutlets incurved on the margms and separated 



by open spac&s. 30. O. paradoxa. 



Fruit ovoid-conic; nutlets toucliing. 



Kidges of the nutlets honevcomb-crested ; inflorescence narrow; leaves 



canescent and liispid. 31. O. eulophus. 



Ridges of the nutlets neither much interlacing nor crested. 



