168 IOWA ACADEMY OF SCIENCE 



* 



5. Very thin, black, winged, with 1-2 fine longitudinal 



striations, broadest toward apex (fig. VI) 



Lactuca canadensis L. 114 



5. Thicker, not winged. 

 6. Plano-convex or concavo-convex, broadest at mid- 

 dle, tapering at both ends almost equally (fig. 



XXX) Daucus Carota L. 61 



6. Not tapering equally at both ends. 



7. One side covered with prickles not arranged in 



lines, irregular in shape 



Lappula virginiana (L.) Greene 66 



Without spines. 



8. With 4 to 5 longitudinal striations, tapering 



more acutely at apex, red 



Impatiens biflora Walt. 54 



8. Without longitudinal striations, not red. 

 9. Plump, light brown with purplish blotches, 



no prominent notch at hilum 



Amphicarpa monoica (L.) Ell. 52 



9. Slightly concave on each side with a pro- 

 nounced notch at hilum, short kidney- 

 shaped (fig. XXXVIII) 



Abutilon Theophrasti Medic. 55 



. 3 to 4 mm. long. 

 II. At least twice as long as broad. 

 1. With more than one persistent terminal appendage. 

 2. 1 to 4 awns at apex. 



3. Awns y-2 length of achene Bidens cernua L. 94 



3. Awn less than y 2 length of achene Bidens connata L. 



2. With more than 4 terminal appendages. 



3. With a double row of chaffy scales at apex (fig. II) 



Cichorium IntybuA L. 107 



3. With a pappus of capillary hairs at apex. 



4. Seed light straw-colored and obliquely truncate at 



base, thick set (fig. XXXI) . . .Centaurea Cyanus L. 106 



5. Dark brown, very slender and somewhat square in 



cross section Inula Helcnium L. 85 



3. Terminal appendages short and stiff. 



4. Top-shaped with spines arranged in a ring around 



the top and with one in the center 



Ambrosia artemisiifolia L. 87 



4. Somewhat spindle-shaped with 12-14 longitudinal 

 ridges notched in short spines near apex (fig. XVI) 



Taraxacum officinale Weber 110 



1. Without more than 1 persistent terminal appendage. 



2. Surface shining, rich chestnut brown 



Polygonum virginianum L. 18 



