The Flora of the Cayuga Lake Basin 189 



h. Plant annual from fibrous roots, not decumbent; spikes elongated, 

 flexuous, very loosely flowered, the greenish white flowers scat- 

 tered down to the upper leaf axils ; stamens 3-8 ; achenes mostly 

 lenticular. 11. P. punctatum 



f. Sepals not glandular-dotted (or only very indistinctly so in no. 12). 

 g. Leaves lanceolate, 1-2 cm. wide; spikes erect; flowers 2-3 mm. long. 

 h. Plant conspicuously strigose ; sheaths often with an herbaceous 



border; achenes lenticular. (See nos. 7 and 8.) 

 h. Plant sparingly strigose or glabrous ; sheaths without a border. 

 i. Flowers clear white or pink ; stamens 8 ; achenes triangular ; leaf 

 blades mostly rounded or obtuse at base ; perennials of wet 

 places. 12. P. hydropiperoides 



i. Flowers dull pale greenish purple or greenish white ; stamens 6 ; 

 achenes lenticular or triangular ; leaf blades acute at base, often 

 with a dark spot near the middle; annuals of drier places. 



13. P. Persicaria 

 </. Leaves broadly ovate, acuminate; spikes stout, deep purple, nodding; 

 flowers 3-5 mm. long; sheaths often with a spreading herbaceous 

 border; puberulent annuals. 14. P. orientale 



d. Styles long, stiff, exserted, persistent, deflexed, and hooked at tip in fruit ; 

 spikes very long and slender, rigid, greenish; leaves ovate, acuminate. 



15. P. z'irginiatium 

 b. Stems armed with hooked prickles, reclining. 



c. Leaves sagittate; styles 2; achenes lenticular. 16. P. sagittatum 



c. Leaves hastate; styles 3; achenes 3-angled. 17. P. ari folium 



a. Stems twining ; leaves broadly ovate, cordate at base. 



b. Nodes naked ; angles of the calyx keeled ; leaves glabrous, often scabrous on the 

 veins beneath. 

 c. Calyx sharply angled ; achenes dull ; leaves triangular-ovate, the basal lobes 



acute ; annuals. 18. P. Convolvulus 



c. Calyx wing-angled ; achenes glossy ; leaves more heart-shaped in outline, the 

 basal lobes more rounded ; perennials. 19. P. scandens 



b. Nodes bristly-ciliate ; angles of the calyx obscurely keeled ; leaves puberulent 

 beneath; achenes glossy; perennials. [P. cilinode] 



1. P. aviculare L. Knotweed. 



A weed of roadsides and waste places, mostly in gravelly soils, also about salt 

 springs ; common. July-Oct. 



Almost throughout N. A. Found also in Eurasia. 



As a weed, introduced ; but native about salt springs and elsewhere. Extremely 

 variable in size of leaves, the forms with larger leaves being probably the var. 

 vegetum Ledeb. ; but too many transitional forms occur, and size of leaf seems to 

 depend too much upon environment, to justify the recognition of the variety as a 

 distinct race in the Cayuga Lake Basin. 



2. P. erectum L. 



A weed of rich roadsides, borders of fields, and waste places; frequent. Aug.-Oct. 

 Ont. to Alberta, southw. to Ga., Colo., and Tex.; infrequent or rare on the Coastal 

 Plain. 



3. P. RAMOSISSIMUM MicllX. 



A weed about the new Drill Hall, C. U. campus, 1916 and later. July. 



Me. and Mass., local; w. Pa., and from 111. to Minn., Tex., N. Mex., and Calif. 



Formerly unknown at this station, and undoubtedly introduced. 



