1^ 



Clarence J . Elmore 



g. More than 30 m long. 



21. A^ percgrina. 

 gg. Less than 30 m long. 



22. A^. Diciiiscnhis. 

 ff. Rostrate-capitate. 23. A'', saliiiarum. 



ce. Narrowly lanceolate. 24. N . cincta. 



dd. Middle striations not alternately long and short. 



c. Middle striations equally shortened forming a pseudo- 



stauros. 25. A^. gracilis, 



ee. No pseuddstauros. 



/. Apices not rostrate-capitate. 



g. Broadly lanceolate, central nodule surrounded 

 by a large hyaline area. 

 h. Apices not rostrate. 



26. A'', vulpina. 

 hh. Apices rostrate. 



27. A'^. viridula. 



gg. Narrowly lanceolate, hyaline area small. 



28. A^. radiosa. 

 ggg. Elliptical-lanceolate. 



29. A^ cryptoccphala. 

 ff. Apices rostrate-capitate. 



g. Hyaline area elongated transversely. 



29. N. cryptoccphala. 

 gg. Hyaline area round. 



30. A'^. rhynchoccphala. 

 hb. Striations very coarse. 31. N. hungarica. 



AA. Middle striations radiate, terminal perpendicular to the raphe. 

 /'. Narrowly lanceolate, hyaline area not stauroneiform. 



32. A', digito-radiata. 

 bb. Broadly lanceolate, elliptical, or oblong. 

 * c. Broad!}' lanceolate, striations coarse, hyaline area stauroneiform. 



S3. N. 1-cinhardtii. 

 cc. Small with fine striations, hyaline area rounded. 



34. A^ Diiiuicivaukonoisis. 

 AAA. Striations all radiate. 

 /'. Lanceolate to elliptical. 



c. No pseudostauros. 35. A'. Uniccolata. 



cc. With pseudostauros. 



d. Middle striations alternately long and short. 



36. A', gastnuji. 

 dd. Middle striations not alternately long and short. 

 c. Capitate. 37. N. anglica. 



cc. Not capitate. 38. A". placoihiJa. 



bb. Oblong. 



