A SECOND OHIO WEED MANUAL. 295 



III. Perennials (P) live year after year without renewal from 

 another source. They grow from seeds, or from rootstocks and 

 subterranean stems; once started they continue in the same spot or 

 spread about it. All w r oody stemmed pests like briers, sassafras, 

 roses, etc., belong- here. But of the herbaceous perennials we have 

 two classes according to underground propagation: 



1. The pests with creeping or underground stems, by which 

 the plant spreads: Horse nettle, Canada thistle, toad-flax, mints, 

 moneywort, field bindweed, common bindweed, cypress spurge and 

 bouncing-bet illustrate these features. 



2. Perennials with ordinary roots and not spreading under- 

 ground. Bulbous and tap-root weeds are in this class. Chicory, 

 goldenrod, aster, vervains, motherwort, broad and narrow plantain 

 and mallow have this character of root. 



Lists of "worst," "bad" and "indifferent" weeds are of great 

 interest, yet the plants in a list of "worst" weeds can not usually 

 claim a wide range. Sorrel is the worst weed upon the Station farm 

 when a period of 3 r ears is considered. Other locations will quite 

 likely exhibit an adaptation to some other plant and therefore show 

 some other "worst" weed. There are about one hundred weeds in 

 Ohio that are always troublesome. Indifferent weeds are simply of 

 less importance, for the time, than the plant under culture. 



VITALITY OF WEED SEEDS. 



Weeds spring up sometimes in a most perplexing manner. 

 After two seasons of comparative freedom from white-top, Erigcrou 

 annuus L., in clover, the fields were white with it in the summer of 

 1897. Similarly, white clover may cover nearty all old grass lands. 

 Chess grows in wheat, mustards in clover, chickweed and shep- 

 herd's purse in gardens and ragweeds in wheat stubble about as 

 often as the wheat rotation is repeated. An old hut is cleared away 

 and new plants come into life where it stood. Earth from ditches, 

 from wells and from cisterns is scattered but to bring forth strange 

 growths. Hasty conclusions may easily be drawn from these oc- 

 currences. It would appear possible to explain most of them upon 

 natural grounds. Take the example of white-top in clover fields: 

 the season of 1896 was one of abundant rains throughout. We have 

 but to conceive of the presence of seeds in the soil, a reasonable 

 assumption based upon the seed's powers of dissemination, which 

 germinated under the continued warmth and moisture. The same 

 explanation appears to hold good for white clover and accounts for 

 its prevalence. Sorrel likewise was unusually prevalent. It has 

 been found by Dr. Beal, 1 that shepherd's purse, peppergrass, May- 



l Agricultural Science, 8: 283 ■ 



