A SEED KEY TO COMMON WEEDS 383 



4. Under 1.8 mm. long. 



5. Light straw-colored, slightly flattened on one side, 



see description Panicum capillare L. 2 



5. Not light straw-colored. 



6. With a pronounced groove running up one side 



and onto the end. . . .Sisymbrium officinale Scop. 41 

 6. Without a groove. 



7. Surface finely reticulate Plantago major L. 77 



7. Surface finely pitted Barbarea vulgaris R. Br. 



3. Surface dull. 



4. Surface covered with pits or tubercle-like projections 

 easily visible with hand lens. 

 6. Shallow pitted or granular. 



7. Granular, usually flesh-colored, light 



Cuscuta arvensis Beyrich 65 



7 Distinctly pitted, not flesh-colored. 

 8. Irregularly flattened; convex at scar with a 

 slight concavity on either side near scar 



(fig. XXXIX) Barbarea vulgaris R. Br. 42 



8. Not flattened markedly, scar not as noticeably 

 convex, duller in color than the next preced- 

 ing Brassiea nigra L. Koch. 40 



6. Deeply pitted in longitudinal rows (fig. XXIV) 



. .Verbascum Thapsus 74 or Verbascum Blattaria 7.~> 

 5. Surface with tubercle-like elevations. 

 6. Round to short kidney-shape. 



7. Distinctly red in color, usually not over 1.2 mm. 

 in diameter, somewhat angular with about 5 

 rows of tubercles on each face (fig. XXXIV) 



Stellaria media L. Cyril. 29 



7. Not usually distinctly red in color, over 1.2 mm. 

 in diameter. 

 8. Background of seed brown, rarely reddish, not 



angular, short kidney-shaped 



Silene noctiflora L. 33 



8. Background of seed distinctly black or dark 

 gray, somewhat more angular and larger 



than next preceding Lychnis alba Mill. 32 



6. Seeds not at all kidney-shaped, ridges not dis- 

 tinctly tubercled (fig. XXIV) 



Verbascum Thapsus L. 74 or Verbascum Blattaria L. 75 

 4. Surface not pitted or tubercled. 



5. Wafer-like, thin especially at the edges. 



6. With longitudinal lines (fig. XXX) 



Daucus Carota L. 61 



6. Without longitudinal lines. 



7. Without projections on the margin, usually 

 narrowly winged with a groove on each side 

 Arabis laevigata Muhl. Poir. 43 



