294 OHIO EXPERIMENT STATION: BULLETIN 175. 



Weedy plants become introduced unintentionally, in seeds, in 

 packing material, and so forth. The catchfly just mentioned came 

 in crimson clover seed; the Russian thistle in flax seed, while 

 bracted-plantain, Croton, and gum-weed have been introduced in 

 many Ohio counties in western clover and alfalfa seed. Prickly let- 

 tuce is dispersed in this manner; charlock and spreading- mustard 

 are scattered in oats, the latter by sticking in the slit, while sorrel, 

 narrow plantain, panic-grasses, foxtail and others, are similarly dis- 

 persed. Once within a region, weeds become scattered by many 

 special means. Some are spread through the enclosing parts of the 

 seeds that attach them to animals by means of prickles, like cockle- 

 bur, sticktights, tick-trefoil, Spanish needles, beggar's-lice, hound's 

 -tongue, agrimony and bur-grass. Yet other seeds are provided 

 with a hair-like parachute to render them buoyant and thus be 

 readily transported by the wind. Dandelion, thistles, milkweed, 

 dogbane, prickly lettuce, asters, goldenrod and white-top have this 

 abundant attachment to insure them wide dissemination. Oc- 

 casionally weed seeds are provided with wings, as in the case of 

 toad-flax and spurry; the catalpa among the trees has similar wings. 

 One of the unusual adaptations is in the case of spreading mustard 

 seeds which are so small as to become lodged in the slit of oat 

 seeds. 



CLASSES OF WEEDS. 



Weedy plants are classified according to their life period: 



I. Annuals, marked (A) in the weed list, are those weeds which 

 grow from seed each year or season and die after ripening seeds 

 again. Ragweed, crab-grass, buffalo-bur, pigweed, lady's-thumb, 

 lamb's-quarters, Russian thistle, purslane, foxtail, and a multitude 

 of others are of this sort, and may be called summer annuals. Many 

 of them are troublesome pests. 



Some of the general class are winter annuals. They spring 

 from seed in late summer or fall and survive the winter in the shape 

 of small seedlings. White-top, prickly lettuce, shepherd's purse, 

 spreading mustard, chickweed and dead nettle live over the winter 

 in this manner. Chess, spelt and rye grow in the same way. 



II. Biennials (B) grow from seed but do not produce seed until 

 the second season. Wild carrot, wild parsnip, common thistle, 

 winter-cress, burdock, teasel, sweet clover, hound's-tongue and 

 mullens belong here. . 



