78 GRASSES OF IOWA. 



along the roadside, the seed of this weed having been scat- 

 tered from the farmers' grain wagons." Loliuvi temulentum 

 is another well known illustration where man has acted as a 

 disseminator. This weed was well known to the ancients as a 

 serious pest in grain fields. This weed seldom occurs in this 

 state now. Formerly it was much more common, when Iowa 

 was a wheat-growing state. 



The sand-bur affords another excellent illustration of man 

 as an agent in scattering seeds. During the early days, sand- 

 bur was common along Ihe sandy embankments of streams; 

 now it has becoooe common throughout the state of Iowa, and 

 largely because the sand used for building purposes is obtained 

 from the river bottoms. Then, too, it has been scattered far 

 and wide by the railroads who use the gravel as ballast. 

 Setaria verticillata has for owed and occupied the waste places 

 in many parts of this state, especially in the southern tiers of 

 couaties. It was largely introduced with foreign seed, or as a 

 ballast weed in seaport towns. The common finger-grass 

 {ranicum sanguinale) and pigeon -grass or fox- tail are largely 

 disseminated through the use of clover and other agricultural 

 seeds. Mr F. C. Stewart, some years ago, determined that it 

 was the principal impurity in fifteen samples of red clover 

 grown in various parts of this country. He says of it as fol- 

 lows: "The weed seed most commonly found in clover seed 

 is Setaria viridis. This species appeared in fifty samples, 

 Setaria glauca appearing but thirty-one times, Panicum glabrum 

 twenty-four, ajidi Panicum sanguinale three times." O. Burch- 

 ard* reports that orchard grass in North America contains 

 Panicum capillare, Phleum pratense, Poa pratensis, Arrhenatherum 

 elatius, Bromus erectus, Festuca pratensis, Holcus lanatus, Lolium 

 per^enneand Poa trivialis. Burchardf further stites that "almost 

 every lot of red clover seed from the United States is found to 

 contain, even when thoroughly purified, varying quantities of 

 the following seeds: Panicum crus-galli, Panicum Jiliforme, P. 

 sanguinale, Panicum capillare, Phleum, pratense, Setaria glauca, 

 and S viridis. " We should observe, however, that some of the 

 plants mentioned by this writer do not occur in clover seed, 

 as, for instance, Panicum /iliforme. Bromus mollis, a worthless 

 forage plant, has been widely distributed as a weed, not only 



♦Contributions from botanical laboratory and seed-control station of Hamburg. 

 3: 1893. Abst. Exp. Sta. Rec. U. S Dept. of Agrl. 5: 3.33. 



+The objects and methods of seed Investigation and the establishment of seed-con- 

 trol stations. Exp. Sta. Rec. U. S. Dept. Agrl. 4: 891. 



