NAJADACEAE ([PONDWBED FAMILY) 



71 



i. Mature spikes 1.5-3.5 cm. long- {if rarely long-er, with float- 

 ing leaves 10-l8-nerved). 

 Foliage and spikes strongly suffused with red ; 8 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-'Z mm. long B. P. 



-. Leaves all submersed and similar j. 

 J, Leaves lanceolate, oblong or broader h. 

 Tc. Leaves sessile or short-petioled, not clasping l. 



I. Leaves finely and sharply serrulate 18. P. 



/. Leaves entire, but sometimes with puckered or undulate, not 



serrulate, margins m. 

 m. Mature spike 8.8-5.5 cm. long. 



Fruit distinctly 8-keeled 



Fruit with rounded, scarcely keeled sides .... 



711. Mature spike shorter n. 



71. Spike more than 1 cm. long. 



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

 pels of each flower usually ripening .... 



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

 «.. Spike 4-7 mm. long ... . ... 



k. Leaves clasping or half-clasping o. 



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



stipules conspicuous i^nd persistent ; fruit sharply keeled . 



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



stipules inconspicuous or soon reduced to shreds; fruit 



rounded on the back or obtusely keeled p. 



Leaves undulate or crisped, with 8-7 prominent nerves ; jfruit 



8.5-4.5 mm. long. 



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



, .attenuate 14. i*. 



Stipules short and inconspicuous ; leaves from suborbicular 



to oblong- lanceolate 15. 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. 



11. 

 12. 



alpinus. 



heterophyllue. 



pol/ygo7iifoliU8. 



criapua. 



anguatifoHud. 



18. P. 



P- 



P- 



heteroph/yll/us. 

 mysHcus, 



praelongus. 



Richardsonii, 



perfoliatua. 



zo8terifoliu<s. 

 acuiifoliufi. 



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, without 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. «. 

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

 the principal leaves. 

 Peduncles equaling or exceeding the spikes . . . . 82. P. h^britpua. 



Peduncles shorter than the spikes 88. P. " 



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

 branches i. 

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

 v,. Leaves with veiT many fine nerves. 



Spikes many-flowered, in fruit 1.5-8 cm. long . . 19. P. 



Sfiikes 4r-S-iio\vered, in fruit .^-8 mm. long . . .20. P. 

 ■w. Leaves with 3-T nerves -y. 



D. Mature fruit 3.5-4.5 mm. long. 



Stipules 0.5-1 cm. long; leaves acute ; spikes capitate 21. P. ffillii. 

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



spikes subcylindric-ovoid 22. P. 



7). Mature fruit 2-3 mm. long w. 

 w. Bases of the leaves bearing translucent glands ; fruit 

 plump, obscurely or bluntly keeled. 

 Leaves &-7-nerved; stipules 1-2 cm. long . 28. P. 



Leaves 3-nerved ; stipules less than 1 cm. long . 25. P. 

 w. Bases of leaves gKndless ; fruit flattened, with a thin 



keel or crest , . . . (30) P.foUosv^, 



t. Principal leaves less than 1 mm. broad oj. 

 X. Plant beai'ing winter-buds formed by the hardened ends of 

 branches closelj I^lvested by imbricated leaves and 

 stipules y. 

 y. Winter-buds born' primarily on very short axillary 

 branches. 

 Leaves of the winter-buds widely divaricate 

 Leaves of the wii-ter-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, 

 Leaves rigid, revolute ; winter-buds 1t2 cm. long . 24. P. 

 Leaves soft; wjuter-^q(j8 fiboiitl prq. |on^ . 25. P. 



Frieaii. 

 puailhis. 



. 7i4agarensia. 



P. lateralis. 

 P. 



27. 



28, P. gemmiparua 



strictifoU 

 pusillus, 



