498 



WEED FLORA OF IOWA 



1 



U/fc a 



Fig. 376A Fig. 376A1 Fig. 376B Fig. 376C 



Fig. 376. Seeds of Picris and Tragopogon. A and Al. Bristly Ox-tongue 

 (Picris echioides) . B. Oyster Plant (.Tragopogon porrifolius) ; a, achenes 

 enlarged, b, achenes natural size. 



C. Meadow Salsify (Tragopogon pratensis) . 



(A, drawings by L. R. Collins ; B, after Hillman, Bull. Mich. Agr. Exp. Sta. ; 



C, drawing by C. M. King.) 



Dark-seeded Dandelion (Taraxacum erythrospermum Andrz.). 



Achenes one-sixth to one-fifth in. long; lance-shaped, or spindle- 

 shaped, 5 longitudinal ridges, upper end with rough tubercles, per- 

 sistent long beak about two-fifths in. long, brownish, somewhat 

 pointed, prominently ribbed ; pappus of numerous capillary, fragile, 

 white bristles ; color reddish ; toothed at apex ; beak and pappus both 

 shorter; achenes more prominently tubercled than in T. officinale. 



#* 



a 



Fig. 377A Fig. 377B 



Fig. 377. Dandelion seeds. A. Red Seeded Dandelion (Taraxacum erythros- 

 permum) ; a, seed enlarged, b and c, seed, natural size, c, with pappus. 



B. Common Dandelion (Taraxacum officinale). A, an enlarged view of one 

 of the two similar faces of an achene, in which no attempt is made to show 

 the minute surface-scales which are not evident under the ordinary lens. 

 B, a group of seeds, natural size, b, one bearing the beak and pappus. C, 

 a group showing common variation in the form of the achenes. 



(After Hillman: A, Bull. Mich. Agr. Exp. Sta.; B, Bull. Nev. Agr. Exp. Sta.) 



