PLATE I. 



Each magnified abozit j diameters. 



1 Sorghum Halepense (L) Pers Johnson -grass, 2 seeds. 



2 Syntherisma sanguinalis ( ..) Du.a~ Crab-grass, 4 seeds. 



3 Syntherisma linearis (Krock) Nash Small Crab-grass, 2 seeds. 



4 Panicum capillar e L. Old Witch-grass, 4 seeds. 



6 Agropyron repens (L) Beauv Quack-grass, 2 seeds. 



6 -Poa compressa L Wire-grass, 2 seeds. 



7 -Poa an?iua L May -grass, 2 seeds. 



8 Chactochloa glauca (L) Scribn Yellow Foxtail, 4 seeds. 



9 Chactochloa viridis (L) Scribn Green Foxtail, 4 seeds. 



10 Chactochloa -verticillata (L) Scribn Whorled Foxtail, 2 seeds. 



11 Chaetochloa Italica (L) Scribn Italian Millet, 2 seeds. 



12 Echinochloa Crus-galli (L) Beauv Barnyard-grass, 4 seeds. 



13 Panicum miliaceum L Millet, 2 seeds. 



14 Eleusine Indica (L) Gaertn Dog's-tail Grass, 2 seeds. 



15 Phleum pratense L Timothy, 4 seeds. 



16 Eragrostis major Host Stinking-grass, 4 seeds. 



17 Phalaris arundinacea L Reed Canary-grass, 2 seeds. 



18 Fcstuca elatior L Meadow Fescue, 2 seeds. 



19 Bromus secalinus L Chess, 2 seeds. 



20 Scirpus Americauus Pers Club-rush, 2 seeds. 



21 Scirpus atrovirens Muhl Dark-green Bulrush, 2 seeds. 



22 Car ex lurida Wahl Sallow Sedge, 2 seeds. 



23 Urtica gracilis Ait Slender Nettle, 4 seeds. 



24 Polygonum aviculare Li Knot-grass, 4 seeds. 



25 Polygonum Persicaria L Lady's- thumb, 4 seeds. 



26 Polygonum Pennsylvanicum L Pennsylvania Smar tweed, 4 seeds. 



27 Polygonum sagittatum L Tear-thumb, 2 seeds . 



28 Polygonum hydropiperoides Michx Mild Water Pepper, 2 seeds. 



29 Rumex altissimus Wood Tall Dock, 4 seeds, 



30 Rumex salicifolius Weinm Willow Dock, 2 saeds. 



From original photographs by P. A. Hinman and J. M. Van Hook. 



