w 



Bickxell: Ferns and flowering plants of Nantucket 445 

 P. avicidare van depressum Meisner in DC. Prod. 14 : 98. 



1856. 



/ 



Me 



Frequent along roads and pathways. 



Pale glaucescent green, prostrate ; stems stiff, becoming some- 

 what lignescent, often of nearly uniform thickness throughout, bear- 

 ing short, divergent branches nearly to the tip, or sometimes with 

 elongated branches with short and stiff ultimate divisions ; inter- 

 nodes very short, sharply angled ; ochreae very short, brownish- 

 tinged, becoming bright light-brown, finally cleft into rather broad, 

 weakly acuminate divisions; leaves small, numerous, crowded, 

 mostly 0.5-1 cm. long, 2-3 mm. wide, oval, elliptic, or short- 

 oblong, obtuse or rounded at the apex, contracted or narrowed to 

 a very short rather broad petiole, thickish, strongly venose beneath, 

 scarcely revolute, mostly with involute tendency, often minutely 

 crisped; flowers small, crowded, appearing subsessile, 2-2.5 ^^"^• 

 long, at maturity sometimes. as broad as long, green, the divisions 

 narrowly w^hite-margined or tinged with reddish-purple ; achene 

 included, mostly broadly ovoid, usually abruptly contracted above, 

 obtusely pointed, unevenly trigonous or sublenticular, 2-2.5 "^^• 

 long, 1. 25-1. 75 mm. wide, dark brow^n, finely rugulose-striate, 

 dull or sometimes obscurely rugulose and somewhat shining. 



A smaller plant than Polygonum avicidare^ commonly stiffly 

 prostrate, with relatively thicker, more woody stems of shorter, 

 more angled inter nodes, much smaller, thicker, more venose leaves, 

 mostly oval or short-oblong and obtuse, smaller, more crowded 

 flowers on shorter pedicels, smaller and somewhat different 

 achenes. 



The Polygonum littorale Link, of Europe, to which this plant 

 has been referred, appears to be quite distinct. Specimens labeled 

 by Meisner in the herbarium of the New York Botanical Garden 

 differ obviously, among other characters, in the smaller, brighter 

 reddish-brown achene, which is narrower, more gradually pointed, 

 smooth, or nearly so, more or less shining, and distincdy exposed at 

 the tip when fully mature. That Polygonum littorale also occurs in 

 this country seems to be attested by specimens from Mt. Desert, 

 Maine, which I have been unable to refer to any other species. 



"*" Polygonum provinciale C. Koch. Linnaea 22: 204. 1849. 



Similar to Polygonum buxiforme Small, but more slender and 

 and often longer-branched, the internodes usually rather longer 



