SCATTERING OP WEEDS 



631 



Fig. 494B 



Fig. 494. Scattering of seed by wind. A. The Iowa Tumble Weed (Amaranthus 

 graecizans) . The weeds piled up against the fence; the Russian Thistle and 

 other weeds are scattered in a similar way. B. Achene of Red-seeded 

 Dandelion. 

 (A, after Bergen's Botany — Ginn & Co. ; B, drawing by Ada Hayden.) 



Seed coat or its appendages. 



a. Coma of hairs — milkweed. 



b. Mucilaginous — peppergrass. 



c. Contractile seed coat — oxalis. 

 Receptacle. 



a. Fleshy — rose. 

 Bracts — basswood. 

 Involucre. 



a. Spiny — burdock, cocklebur. 



