THE GENERAL CHARACTERS OF SEEDS 



425 



III 



Figure 258A 



Figure 258B 



Fig. 258. A. Hemp (Cannabis sativa). I. Seed in envelope. II. Seed witlioui 



envelope. III. Cross section of seed. F. pericarp ; S. testa ; B. endosperm. 

 B. Nettle CUrtica gracilis), a, seed in envelope; b, seed enlarged; d, natural 



size, 

 (A, after "Winton ; B, after Hillman, Bull. Mich. Agr. Exp. Sta.) 



Nettle {Urtica gracilis Ait.). 



The fruit enclosed in membranous calyx ; seed pale straw-color, 

 1 mm. long, flattened, ovate, slightly pointed toward the ends, 

 smooth; point of attachment at broader end. 



POLYGONACEAE, BUCKWHEAT FAMILY. 



Sour Dock {Bumex acetosa L.). 



Inner sepals of calyx in fruit, with wings; aehene convex be- 

 tween angles; one-twelfth in. in length, variable, smooth, shining; 

 dark reddish brown. Probably occurs in European grown clover 

 seed. 



Sheep Sorrel (Bumex acetosella L.). 



Calyx usually persistent, not wing-mar^ned in fruit, roughened, 

 with prominent veins; closely fitting aehene, elliptical or ovate 



