22 BULLETIN 692, U. 8. DEPARTMENT OF AGRICULTURE. 
of redtop, Rhode Island bent, and colonial bent. By the same 
means, the seeds of velvet bent can be recognized when occurring 
in South German mixed bent seed. 
IMPURITIES OF COMMERCIAL SEED. 
An examination of many commercial samples of the seeds of redtop 
and of South German mixed bent shows that their origin, whether 
domestic or foreign, can usually be determined. The studies of the 
writer in this connection include domestic redtop seed, redtop im- 
ported from Europe, South German mixed bent seed imported from 
Germany, Holland, and England, and a limited number of samples 
of Rhode Island bent seed from Rhode Island and of colonial bent 
seed from New Zealand. The samples of domestic redtop seed and 
of South German mixed bent seed examined were sufficient in number 
to show the prevailing kinds of incidental seeds occurring with these 
commercial seeds. A smaller number of samples of redtop seed 
an 
Rumex acetosella Cerastium vulgatum = Veronica arvensis Achillea millefoliun. 
Fia. 9.—Seeds occurring frequently in both American-grown redtop seed and South German mixed bent 
seed (enlarged and natural size): 1, Sorrel (Rumer acetosella); 2, mouse-ear chickweed (Cerastium vul- 
gatum); 3, corn speedwell ( Veronica arvensis); 4, yarrow (Achillea millefolium). 
known to have been imported from Europe, 27 in all, represented, all 
that were available. The result of the examination of the samples 
of Rhode Island bent seed is supported by observations by the writer 
of the various plants occurring in fields in Rhode Island, where the 
Rhode Island bent grass grows abundantly. 
Among the incidental seeds found in domestic redtop seed and in 
South German mixed bent seed certain kinds are common to both. 
This is to be expected, since these incidental seeds occur commonly 
with other kinds of commercial seed of both domestic and foreign 
origin, owing to the cosmopolitan character of their plants. Four of 
the kinds found most frequently are shown in figure 9. Exclusive 
of these kinds, others are confined almost wholly to the domestic 
redtop seed (fig. 10), and still others are confined to the South Ger- 
man mixed bent seed (fig. 11). 
The plants represented by some of the kinds of seed considered 
characteristic of EKuropean-grown seed are known to occur in this 
country, but their distribution and the conditions of their growth are 
not such as to lead to the presence of their seed in domestic seed to 
the extent that they appear in the imported seed. Furthermore, the 
