224 CONTRIBUTIONS FROM THE NATIONAL. HERBARIUM. 



Flowers 4 to 6-ranked. 

 Fruit tuberculate. 



Leaves 15 to 30 mm. wide 7. P. amplifolium. 



Leaves 4 to 8 mm, wide 8. P. carneum. 



Fruit not tuberculate. 

 Branches sharply quadrangular. 

 Sepals closely meeting in fruit. 



Spikes pedunculate 9. P. tamaulipense. 



Spikes sessile 10. P, gaumeri. 



Sepals not meeting in fruit. 



Leaves sub.sessile 11. P. guazumae. 



Leaves petiolate 12. P. commutatum. 



Branches terete or compressed. 



Leaves small, 10 to 12 mm. long 13. P. brevifolium. 



Leaves large, 3 cm. long or usually much larger. 

 Leaves thin, shai-ply nerved. 



Leaf blades ovate-oval 14. P. pachyarthron. 



Leaf blades ovate-lanceolate to lance-lineai-. 



Branchlets subterete 15. P. schumanni. 



Branchlets compressed. 



Bracts usually 2 pairs 16. P. purpusi. 



Bracts a single pair 17. P. nervosum. 



Leaves very thick and coriaceous. 



Leaf blades oval-ovate 18. P. reichenbachianum. 



Leaf blades lanceolate to linear. 

 Fruit ovoid. 



Branchlets compressed ; nerves coarse. 



19. P. lanceolatum. 

 Branchlets not compressed ; nerves slender. 



20. P. falcatum. 



Fruit globose 21. P. forestierae. 



Stems without scales on the branches ; leaves sometimes reduced to scales. 



Branches broadly winged 22. P. calyculatum. 



Branches not winged. 



Pistillate flowers 2 to each joint. Phints parasitic chiefly on Pinaceae. 

 Leaves reduced to small scales, not disarticulating. 



Plants puberulent; sjukes several-jointed 23. P. califomicum. 



Plants glabrous; spikes 1-jointed. 



Scales strongly constricted at the base. On Juniperus. 



24. P. ligatum. 

 Scales obscurely or not at all constricted. 

 Scales not constricted ; plants stout, on Juniperus. 



25. P. juniperinum. 

 Scales obscurely constricted ; plants slender, pendent, on Libo- 



cedrus 26. P. libocedri. 



Leaves well developed or sometimes scalelike but disarticulating. 



Leaves scalelike 27. P. minutifolium. 



Leaves well developed. 



Leaves linear or linear-oblong. 



Plants tonientose ; spikes often with 2 or 3 joints. 



28. P. capitellatum. 

 Plants papillose or hirteUous; spikes usually with one joint. 



Staminate spikes about 12-flowered 29. P. tequilense. 



Staminate spikes about 6-flowered 30. P. saltillense. 



