3 64 IOWA ACADEMY OF SCIENCE 



KEY TO SEEDS. 



I. 10 to 20 mm. long. 



1. With more than 1 appendage (figs. XXIX and XIV). 

 2. Covered with hooked spines. 



8. 18 to 25 mm. long XantMum canadensis Hill 88 



3. 10 to 13 mm. long XantMum spinosum L. 89 



2. With appendages at apical end. 



3. With 2 to 4 nearly equal appendages (fig. XXIX) 



Bidens frondosa L. 93 



3. With more than four unequal appendages or spines at apical 

 end (fig. XIV) Ambrosia triflda L. 86 



I. Without more than 1 long appendage. 



2. 10 to 18 mm. long without pappus. Beak 1 to 10 mm. long 



Tragopogon porrifolius L. 108 



2. Beak short, about 4 mm. long Tragopogon pratensis L. 109 



I. 9 to 10 mm. long. 



II. At least twice as long as broad. 



1. With 2 or 3 long equal terminal appendages (fig. XXIX) 



Bidens frondosa L. 93 



II. Not twice as long as broad. 



1. With numerous (4 to 8) unequal terminal straight appen- 

 dages (fig. XIV) Ambrosia triflda L. 86 



1. With numerous (more than 8) terminal hooked prickles 



Agrimonia striata Michx. 45 



I. 8 to 9 mm. long. 

 II. At least twice as long as broad. 



1. With 2 or 3 terminal appendages (fig. XXIX) 



Bidens frondosa L. 93 



II. Not twice as long as broad. 

 1. With numerous terminal appendages. 



2. With 4 to 8 straight appendages (fig. XIV) 



Ambrosia triflda L». 86 



2. With more than S hooked appendages 



Agrimonia striata Michx. 45 



1. Without numerous appendages but with a wing 



Asclepias syriaca L. 62 



1. 7 to 8 mm. long. 



II. At least twice as long as broad. 



1. With 2 to 4 long terminal appendages, flattish (fig. XXIX) 



Bidens frondosa L. 93 



1. Without terminal appendages, deeply grooved up one side (fig. 

 XXIII) Bromxis secalimcs L. 11 



II. Not twice as long as broad. 



1. Triangular in cross section, shining black (figs. XXXV and 

 XXXVI) Polygonum scandcns Michx. 20 



