Colorado Weed Seeds 
By G. E. EGGINTON 
The appearance of weed seeds in lots of field and garden 
seeds is the rule rather than the exception. It is seldom that com- 
mercial seed is free from the seeds of weeds or other crops. How- 
ever, vegetable and flower seeds, and the seeds of cereals or other 
crops in breeding plots, when selected, harvested and threshed 
by hand, are usually free from weed seeds. Occasionally, machine 
threshed and machine hulled seeds (sorghums and alfalfa more 
frequently than other crop seeds) are free from weed seeds. 
A sample of wheat seed may contain one to many species of 
weed seeds. For example, in the samples of Colorado wheat 
examined, there were found 35 species. Wild oats, bindweed, 
poverty weed, wild buckwheat, cow cockle, kinghead, butterfly- 
weed, wild sunflower, and wild rose appeared more frequently than 
others. In the samples of Colorado alfalfa, 72 species of weed 
seeds were found, those of most common occurrence being black 
mustard, small-seeded alfalfa dodder, pigweed, lamb s quarters, 
barnyard grass, gum weed, marsh elder, burning bush, white sweet 
clover, witchgrass, breadroot, curled dock, Russian thistle, and 
green foxtail. From the preceding examples cited it would appear 
that the possibilities of finding absolutely pure seed are extremely 
limited. Such limited possibilities are further shown by the fact 
that wheat and alfalfa are among the cleanest of the machine- 
threshed or machine-hulled crops, with a smaller percentage of 
impurities and a far less extensive range of weed seed species than 
any of the common grass crops such as timothy, red top, and biue- 
grass, or many of the leguminous crops such as red clover, alsike 
clover, and white clover. 
Weed seeds are for the most part disseminated by natural 
means, yet the introduction of new or foreign species is due to the 
