Colorado Weed Seeds 
37 
2. Knotweed {Polygonum 
aviculare L.) (Fig. 46). Seeds 
maroon to black in color, the 
three sides unequal, gradually 
tapering to the acute apex ; seeds 
2-2.5 mm. long, 1. 2-1.8 mm. wide, 
1.2-1.8 mm. thick; part of the 
calyx is often persistent; ridges 
rounded or obtuse. 
Fig 46. Knotweed (Polyg- 
onum aviculare). Achene 
(left), calyx enclosing achene 
(right). X 12. 
3. Pennsylvania Smartweed 
{Polygonum pennsylvanicum L.) (Fig. 
47). — Seeds shiny black, lenticular, 2.5-3 
mm. long, 2.5-3 mm. wide, nearly circular 
in outline, apex a short, sharp point ; part 
of the calyx often persistent. 
Fig. 47. Pennsylvania 
Smartweed (Polygonum 
pennsylvanicum). x 14. 
Fig. 48. Lady’s Thumb 
(Polygonum persicaria). A. 
Achene. B. Calyx enclosing 
achene. x 11. 
4. Lady’s Thumb {Polygon- 
um persicaria L.) (Fig. 48). 
Seeds shiny black, lenticular, 
1.5-2 mm. long, 1-1.5 mm. wide, 
napiform, tapering to a point 
longer and not so abrupt as in 
P. pennsylvanicum, part of the 
calyx often persistent ; 3-angled 
seeds resembling R. crtspus but 
shiny black in color, often appear 
in this species. 
6. GOOSEFOOT FAMILY 
(Chenopodiaceae ) 
Ovary 1-celled, becoming a 1-seeded thin utricle (a small blad- 
dery fruit) or rarely an achene; pericarp thin or coriaceous (leath 
ery in texture) ; embryo coiled into a ring, entirely or partly 
around the mealy albumen (endosperm.) tvhen albumen is present. 
