1963] 



BOTANY OF THE GUAYANA HIGHLANDS PART V 



J 3 



3. Leaves only slightly shorter than the scape, 2.5 mm wide; basal sterile bracts 



few, suberect. 5. X. spruceana. 



2. Basal bracts not f oliaceous ; scape bialate to terete and ecostate. 



4. Spike 1-2 flowered; sterile bracts 9 or 10; basal pair of bracts ecarinate, not 



cuspidate, exceeding the remainder of the spike; sepals 5.5 mm long. 



6. X. cryptantha. 



4. Spike several-many-flowered ; sterile bracts few. 



5. Scapes 5-15 cm high; lateral sepals 3-3.3 mm long, finely ciliate. 7. X. uleana. 

 5. Scapes 25-50 cm high; lateral sepals 7 mm long; tufted at the apex. 



8. X. seubertii. 



Basal bracts short, equaling or more often distinctly shorter than those immediately 

 above. 



6. Dorsal area of the bract lacking or obscure. 



7. Margin of the bract contrasting with the remainder, membranaceous, lacerate. 



8. Bract-margin red, spreading. 9. X. thysanolepis. 



8. Bract-margin hyaline or white, erect. 



9. Bases of the leaf -sheaths dull, not much dilated; blades mostly well over 



1 mm wide. 10. X. hymenachne. 



9. Bases of the leaf-sheaths lustrous brown, abruptly orbicular. 



10. Leaf -blades slightly over 1 mm wide; bracts acute. 11. X. concinna. 



10. Leaf -blades 2-3 mm wide ; bracts broadly rounded. 



11. Margins of leaf-blades glabrous; spikes depressed-subglobose ; flower- 

 bracts granulate. 12. X. submontana. 

 11. Margins of leaf -blades dusty white -ciliate; spikes oblong-subglobose ; 



flower-bracts smooth. 13. X. sipapoa. 



7. Margin of the bract not greatly distinguished from the remainder in texture or 

 color. 



12. Leaf -sheaths abruptly wider than the terete blades. 



13. Leaves flat, smooth; sheaths yellow-brown; bracts initially glabrous. 



14. X. stenophylloides. 



13. Leaves terete, somewhat rugulose toward the base; sheaths dark castane- 

 ous to nearly black; bracts scantily lanulose or ciliate at the apex, 

 glabrate. 15. X. atriceps. 



12. Leaf-sheaths merging gradually with the blades. 



14. Plants long-caulescent; leaves densely imbricate and forming broad frond- 

 like plates. 



15. Scape ancipital ; scapes and leaves ciliate ; leaf -blades obliquely obtuse ; 



bracts decussate, stem simple. 16. X. decussata. 



15. Scape terete or subterete; scapes glabrous; leaf -blades glabrous. 



16. Leaf-blade to 2 mm wide, not contracted at the base, the apex 

 straight ; sheaths wholly or almost wholly brown. 

 17. Sheaths glabrous, sharply carinate; leaves 7-13 cm long; blades 



green, contrasting sharply with the sheaths. 17. X. witsenioides. 



17. Sheaths ciliate, rounded on the back; leaves to 24 cm long; blades 

 dark, not contrasting with the sheaths. 18. X. riparia. 



16. Leaf -blade 3-9 mm wide, contracted at the base; sheaths green ex- 

 cept the extreme base. 



18. Sepals 6.5-7 mm long; leaf -blades 6 mm wide. 19. X. ptariana. 

 18. Sepals 12 mm long; leaf-blades 9 mm wide. 20. X. xiphophylla. 



14. Plants short-caulescent ; leaves not forming distinct plates. 



19. Inflorescence of 2 sessile spikes. 21. X. bicephala. 



19. Inflorescence always simple. 



20. Leaf -blades prominently ciliate. 



21. Scape ciliate on the costae, ancipital. 



22. Spike ovoid, 7-8 mm in diameter ; bracts spirally arranged. 



22. X. roraimae. 



22. Spike globose, 12-17 mm in diameter; bracts more or less 

 decussate. 23. X. albescens. 



21. Scape glabrous. 



23. Leaf -apex straight, abruptly subulate-tipped. 24. X. setigera. 

 23. Leaf -apex more or less falcate, acute, not appendaged. 



25. X. culmenicola. 



