428 WEED FLORA OF IOWA 



Water Smartweed (Polygonum acre HBK.). 



Achenes oblong, thick, generally 3-angled, somewhat lenticular, 

 one-tenth to one-eighth in. in length, smooth, finely reticulated; 

 color dull; base of perianth adhering. 



Dooryard Knotweed (Polygonum a/vicula/re L.). 



Achenes 3-angled, ovoid, acute, sides deeply concave, one-eighth to 

 one-seventh in. in length; color light to dark and reddish brown; 

 surface finely granulated and striated lengthwise. 



Figure 2<i2A 



Figure 262B 



Figure •2620 



Figure 262D 



Fig. 262. A. Water Smartweed {Polygonum acre). 



B, Dooryard Knotweed {Polygonum aviculare). A, group of seeds (achenes) 

 showing the usual forms ; that at the right is one of the smooth, light 

 colored specimens ; B, a group showing the natural size ; C, a cross section 



"showing the relative positions of embryo and endosperm. 



C. and D. Prince's Feather {Polygonum orientale) . 



(A and D, drawn by C. M. King; C, drawn by Ada Hay den ; B, after Hillman.) 



Prince's Feather (Polygonum orientale L.). 



Achenes usually orbicular, flattened, with prominent remnant of 

 style, one-ninth in. in length, finely reticulated ; color dull brown- 

 ish to black; base with large scar; remnant of colored calyx at 

 base. 



