366 IOWA ACADEMY OF SCIENCE 



3. Not uniformly rusty red or golden brown, more than 1.5 

 mm. broad. 

 4. With a deep groove up one side. . .Bromus seca'.inus L. 11 

 4. Without a deep groove up one side. 

 5. Quite pronouncedly 4-faced and uniformly colored 



Heliopsis helianthoides L. Sweet. 90 



5. Not pronouncedly 4-faced, usually mottled in color. 

 6. Usually with 1 or more longitudinal striations, 



quite angular (fig. IV) .. .Arctium minus Bern. 103 

 6. Without longitudinal striations, not angular.... 



Helianthus divaricatus L. 92 



II. Not twice as long as broad. 



1. Triangular in cross section, shining black 



Polygonum scandens Michx. 20 



1. Not triangular in cross section. 



2. With hooked terminal prickles (Bur) 



Agrimonia striata Michx. 45 



2. Without hooked terminal appendages. 



3. Almost globular white fruit Rhus Toxicodendron L. 53 



3. Not globular or white. 



4. Short kidney-shaped, flattened, brown, mottled with 



purple Amphicarpa monoica (L.) Ell. 52 



4. Somewhat fusiform, reddish with 4 or 5 distinct longi- 

 tudinal ridges Impaticns biflora Walt. 54 



I. 4 to 5 mm. long. 



II. At least twice as long as broad. 

 1. Surface shining. 



2. Rich chestnut brown, oval Polygonum virginianum L. 18 



2. Grayish white, obliquely truncate at base (fig. XXXI)... 



Centaurea Cyan us L. 106 



1. Surface not shining. 



2. With numerous longitudinal notched ridges. 



3. Fruit broadest in middle, concavo-convex or plano-con- 

 vex, oval ridges pronounced and notched entire length 



(fig. XXXV) Daucus Carota L. 61 



3. Fruit narrow, broadest toward apical end, oblanceolate, 

 with 12-14 longitudinal ridges pronouncedly notched 

 near apical end (fig. XVI) Taraxacum officinale Weber 110 

 2. Without numerous longitudinal notched ridges. 

 3. Surface smooth, not pronouncedly ridged. 



4. Seeds very light-colored, some faintly blotched with 



dark (fig. XIX) Cirsium lanccolatum L. Hill. 104 



4. Seeds dark, usually mottled. 



5. Quite angular, mottled in transverse lines (fig. IV) 



Arctium minus Berh. 103 



5. Not angular, mottled longitudinally 



Hclianthus divaricatus L. 92 



