NAJADACEAE (PONDWEED FAMILY^ 



71 



n. 



n. 



11. 

 12. 



o. 

 10. 

 IT. 



P. 

 P. 



P. 

 P. 

 P. 



i. Mature spikes 1.5-'^.5 cm. long (if rarely longer, with float- 

 ing leaves lU-lS-nerved). 

 Foliage and spikes strongly suffused with red ; 3 or 4 



carpels of each flower usually ripening . . . 5. P. 

 Foliage and spikes greenish ; 1 (rarely 2) carpels ripening 10. P. 



h. Mature fruit 1.5-i mm. long 3. P. 



a. Leaves all submersed and similar j. 

 j. Leaves lanceolate, oblong or broader k. 

 k. Leaves sessile or suort-petioled. not clasping I. 



I . Leaves finely and sharply serrulate 



L Leaves entire, but sometimes wth puckered or undulate, not 



serrulate, margins m. 

 m. Mature spike 'i.'6-b.h cm. long. 



Fruit distinctly 3-keeled 



Fruit with rounded, scarcely keeled sides .... 

 m. Mature spike shorter n. 



Spike more than 1 cm. long. 

 Foliage and spikes strongly suflFused with red ; 3 or 4 car- 

 pels of each flower usually ripening .... 

 Foliage and spikes greenish ; 1 (rarely 2) carpels ripening 



Spike i-T mm. long 



k. Leaves clasping or half-clasping o. 



o. Leaves half-clasping, elongate, with rounded cucullate tips ; 



stipules conspicuous and pensistent ; fruit sharply keeled 

 o. Leaves cordate-clasping, if elongate with tapering plane tips ; 

 stipules inconspicuous or soon reduced to shreds ; fr"uit 

 rounded on the back or obtusely keeled p. 

 p. Leaves undulate or crisped, with 3-7 prominent nerves ; fruit 

 3.5-4.5 mm. long. 

 Stipules 1-2 cm. long, persisting as shreds ; leaves lance- 

 attenuate 14. P. 



Stipules short and inconspicuous ; leaves from suborbicular 



to oblong-lanceolate 15. P. 



p. Leaves flat, scarcely crisped, with 1 prominent nerve ; fruit 

 2.5-3.2 mm. long; stipules, when developed, short and 



inconspicuous 16. P. 



;. Leaves linear to setaceous q. 

 q. Leaves ribbon-like, 2 mm. or more wide, with a broad coarsely 



cellular-reticulate space each side of the midrib . . . . 4. P. 

 q. Leaves narrower, if occasionally 2 mm. wide, ^vithout a broad 

 cellular-reticulate space r. 

 r. Leaves free from the stipules, or, if slightly adnate to them, 

 bearing globose subsessile or short-stalked spikes in their 

 axils s. 

 s. Fruit flat, cochleate ; the globular spikes borne in the axils of 

 the principal leaves. 

 Peduncles equaling or exceeding the spikes . . . . 32. P. 



Peduncles shorter than the spikes 33. P. 



8. Fruit plump; spikes terminal or borne on the uppermost 

 branches t. 

 t. Principal leaves more than 1 mm. broad u. 

 u. Leaves with very manv fine nerves. 



Spikes many-flowered, in fruit 1.5-3 cm. long 

 Spikes -l-S-rio\vered, in fruit 5-S mm 

 u. Leaves with 3-7 nerves t. 



alpinuH. 



heterophylluH. 



polygonifoliuft. 



18. P. crispus. 



angu^iifolius. 

 lucens. 



alpinvs. 



heierophyllus. 



inysiicuH. 



13. P. praelongua. 



Richardsonii. 

 perfoliaius. 



bupleuroides. 



epihydruH. 



hybriduH. 

 dimorphus. 



long 



w. 



to. 



v. Mature fruit 3.5-4.5 mm. long. 



Stipules 0,5-1 cm. long; leaves acute ; spikes capitate 

 Stipules 1.2-2 cm. long ; leaves obtuse, mucronate ; 



si>ikes subcylindrlc-ovoid 



v. Mature fruit 2-3 mm. long w. 



Bases of the leaves bearing translucent glands ; fruit 

 plump, obscurely or blunth- keeled. 

 Leaves .5-7-nerved ; stipules 1-2 cm. long 

 Leaves 3-nerved ; stii)ules less than 1 cm. long 

 Bases of leaves glandless ; fruit flattened, with a thin 



keel or crest (30) P. foli 



i. Principal leaves less than 1 mm. broad x. 

 X. Plant bearing winter-buds formed by the hardened ends of 

 branches closely m vested by imbricated leaves and 

 stipules y. 

 y. Winter-buds borne i)rimarily on very short axillary 

 branches. 

 Leaves of the winter-buds widelv divaricate 

 Leaves of the winter-buds loosely ascending 

 y. Winter-buds borne at the tips of elongate branches. 

 Leaves bristle-form, with very fine slender tips , 

 Leaves flat or revolute. acute or short-acuminate. 

 I>eaves rigid, levdlutf ; winter-buds 1-2 cm. long . 

 Leaves soft ; ^^ intt^r-hiids about 1 cm long 



26. P. lateralis. 



27. P. Vafieyi. 



2S. P. gemmip(tfnH 



24. 

 25. 



P. xfrictifoliuH. 



P. pUfiUlUH. 



