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 awiculare L.). 



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

 one-seventh in. in length; color light to dark and reddis'h brown; 

 surface finely granulated and striated lengthwise. 



Figure 262A 



Figure 262B 



Figure 2620 Figure 262D 



FiQ. 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 ; G, 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 Hayden ; 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. 



