380 IOWA ACADEMY OF SCIENCE 



13. Kidney-shaped or slightly angular, 

 usually with a deep concavity 



near scar (fig. XXXII) 



Medicago sativa L. 50 



13. Almost uniformly oval. 



14. Usually over 2 mm. long, notch 



near one end 



Melilotus alba Desr. 49 



14. Usually under 2 mm. long, notch 



near center of one side 



Trifolium pratense L. 46 



7. Not compressed. 



8. With about 10 ribs composed of tubercle-like 

 projections, broader at apex, dark (fig. 



XXVII) Anthemis Cotwla L. 97 



8. Without ribs composed of tubercle-like pro- 

 jections. 

 9. With about 9 prominent rounded longitudi- 

 nal ridges, light straw-colored (fig. 



XXVIII) Anthemis arvensis L. 98 



9. Without 9 prominent rounded ridges. 

 10. Surface finely marked throughout. 

 11. Diameter nearly uniform, ends round- 

 ed with rectangular markings 



Hypericum perforatum L. 58 



11. Diameter not uniform, reticulated 

 longitudinally, irregularly shaped... 



Plantago major L. 77- 



10. Surface not finely marked throughout. 

 11. Dark brown. 



12. Cone- or tetrahedral-shaped, usually 

 with white hairs, broadest at one 



end (fig. IX) 



Galinsoga parviflora Cav. 95 



12. Irregularly shaped, no hairs, not 



broadest at one end 



Plantago Rugelii Dene. 78 



11. Light straw-colored, spindle-shaped. 

 12. Scar on one side extending at least 

 one-third length of seed, seed usu- 

 ally over 1.7 mm. long 



Digitaria sanguinale Scop. 1 



12. Scar on one side extending only 

 one-fourth length of seed, seed 



under 1.4 mm. long 



Agrostis alba Schrad. 7 



II. Not twice as long as broad. 



1. Distinctly triangular in cross section. 



