A SEED KEY TO COMMON WEEDS 337 



THE USE OF THE KEY. 



To secure satisfactory results, the key should be used with 

 the drawings as a guide to correct interpretation. To deter- 

 mine a given seed, first rub it vigorously between the thumb 

 and fore finger to remove any loose scales or flower parts 

 which may be adhering. Now determine the length in mili- 

 meters exclusive of any fragile terminal appendage and turn 

 to the group which would include a seed of that length. In 

 this group are two other groups numbered (II). Determine 

 in which of these the seed belongs and continue in a like man- 

 manner until the name of the seed is found. If any char- 

 acter is not plain turn to the picture of a seed described as 

 having that character. 



The writer wishes to thank Prof. W. W. Rowlee, Dr. H. B. 

 Brown and Mr. H. P. Brown for advice and criticism during 

 the progress of the work. 



Descriptions of Seeds Given in the Key. 



Abbreviations: (L)=Length; (W)=Width; (C)=Color; 

 (S)=Shape; (0)=Occurence as an adulterant. 



1. Digitaria sanguined is (L.) Scop. Crab Grass, Finger 

 Grass. L. 1.8 — 2.2 mm. W. .6 — .8 mm. C, light straw to brown 

 or dull green. S., broad spindle shaped to blunt especially at 

 the base; boat shaped; the scar on one side running about one- 

 half the length of the seed : outer chaff usually present, the 

 outer scale being as long as the seed and three-ribbed, the 

 inner about one-half the length of the seed. "Edges of floral 

 groove smooth" Beal. O., sometimes very troublesome, com- 

 mon in clover grass and alfalfa seeds. Introduced from 

 Europe. For drawing see Harz p. 1258, fig. 166, XXIII-XXV. 



2. Panicum capillars L. Old Witch Grass. Tickle Grass, L. 

 1.2 — 1.8 mm. W. .8 — 1.5 mm. C, greenish yellow, glossy, dark 

 in the middle and lighter at the ends. S., oval to elliptic and 

 slightly flattened ; glume with five fine longitudinal nerves, 

 inner glume with two fine longitudinal lines. 0., a common 

 tumbleweed, common in alfalfa and the grasses ; rather unim- 

 portant. Native. 



3. Echinochloa cruss-galli (L) Beauv. Barn-yard Grass. L. 

 2.2 — 3.2 mm. W. 1.3 — 2.8 mm. C, shining gray brown to 



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