AS AIDS IN THE DETERMINATION OF SPECIES. 51 



A. Vessels of "Wood relatively large — 



5. E. cornnta. 



6. E. tetraptera. 



7. E. obliqua. 



8. E. guiuiii. 



9. E. megacarpa. 



10. E. macrorrhyncha. 



11. E. globulus. 



B. Vessels of Wood small — 



12. E. alpina. 



13. E. viminalis. 

 b. Hard Bast feebly developed — 



A. Vessels of Wood relatively large — ■ 



14. E. leucoxylon. 



15. E. grossa. 



16. E. occidentalis. 



B. Vessels of Wood small — 



17. E. cornuta var. lehmanni. 



18. E. obcordata. 

 2. Cortical Cavities small — 



a. Hard Bast well developed — 



19. E. stuartiana. 



20. E. melliodora. 



b. Hard Bast feebly developed — 



21. E. amygdaliua. 



22. E. rostrata. 



23. E. nidis. 



24. E. tereticornis. 



B. Leaves unequally green on both sides — 



1. Cortical Cavities large — 



a. Hard Bast well developed — 



25. E. gomphocephala. 



26. E. marginata. 



b. Hard Bast feebly developed — 



27. E. saligna. 



28. E. punctata. 



2. Cortical Cavities, small — 

 Hard Bast feebly developed — 



29. E. corynocalyx. 



30. E. diversicolor. 



