268 OHIO STATE ACADEMY OF SCIENCE. 



22. Bracts not especially glandular, stipules seldom present, 

 capsules less than 6 mm. long. 23. 

 23. Stigmas sessile, capsule blunt, flowers often fascicled on the 

 rhachis with a distinct interval between the fascicles, 

 bracts green; shrub in dense clumps. 5. interior. 



23. Stigmas on a short style, capsules pointed, flowers not fas- 

 cicled. 24. 

 24. Sprawling shrub. S. cordata. 



24. Trees in clumps with few stems or single. 25. 

 25. Leaves green, reticulate venation very fine, bark brown, 

 undeveloped stages of 5". nigra. 



25. Leaves glaucescent, venation coarse, bark yellow or 

 green. 26. 

 26. Leaves glabrescent. 5. fragilis. 



26. Leaves pubescent, young stages of 5. alba. 



Field Key Based on Mature Leaves and Habits.* 



1. Leaves alternate. 2. 



1. Leaves opposite, oblanceolate, nearly sessile, stiff ascend- 

 ing, purplish green; shrub with long slender branches. 



5. purpurea. 

 2. Secondary and tertiary veins prominent by transmitted 



light, unless concealed by tomentum. 3. 

 2. Secondaries and tertiaries almost obliterated with age, 

 primaries distant, running into a strong marginal; 

 leaves narrowly oblong, serrate with distant spin- 

 ulose teeth or entire; often forming dense slender 

 stemmed clumps. 5. interior. 



3. Leaves persistently pubescent. 4. 

 3. Leaves glabrous unless very young. 18. 



4. Pubescence not concealing the upper surface. 6. 

 4. Both surfaces hidden, at least' till mature, by a thick 

 coat of tomentum; shrubs growing in exposed 

 places. 5. 



* Note. This key is constructed for mature well developed leaves. 

 It will not hold for leaves which have not acquired their full size or ven- 

 ation, nor for those of water-shoots and suckers. In immature leaves the 

 primaries are usually more ascending, the other veins not well developed; 

 and the leaf is commonly relatively broader and blunter than when mature. 

 Frequently the two or three terminal leaves of a twig do not assume the 

 character of the species so that one must be careful not to be misled 

 by them when they are different from those lower down on the twig. The 

 leaves of water-shoots are so characterless that it is often difficult for 

 an expert to determine them certainly. They are all thin, green on both 

 sides, lacking both the pubescence and glaucescence which may render the 

 normal leaves distinguishable. 



