THE PERTINACITY AND PREDOMINANCE OF WEEDS. 1 



A weed is defined by the dictionaries to be " Any useless 

 or troublesome plant." " Every plant which grows in a field 

 other than that of which the seed has been (intentionally) 

 sown by the husbandman is a weed," says the " Penny Cyclo- 

 paedia," as cited in Worcester's Dictionary. The "Treasury of 

 Botany" defines it as "Any plant which obtrusively occupies 

 cultivated or dressed ground, to the exclusion or injury of 

 some particular crop intended to be grown. Thus, even the 

 most useful plants may become weeds if they appear out of 

 their proper place. The term is sometimes applied to any in- 

 significant-looking or unprofitable plants which grow profusely 

 in a state of nature ; also to any noxious or useless plant." 

 We may for present purposes consider weeds to be plants 

 which tend to take prevalent possession of soil used for man's 

 purposes, irrespective of his will ; and, in accordance with 

 usage, we may restrict the term to herbs. This excludes pre- 

 dominant indigenous plants occupying ground in a state of 

 nature. Such become weeds when they conspicuously intrude 

 into cultivated fields, meadows, pastures, or the ground around 

 dwellings. Many are unattractive, but not a few are orna- 

 mental ; many are injurious, but some are truly useful. 

 White Clover is an instance of the latter. Bur Clover (J!/e- 

 dicago denticulated) is in California very valuable as food for 

 cattle and sheep, and very injurious by the damage which the 

 burs cause to wool. In the United States, and perhaps in 

 most parts of the world, a large majority of the weeds are 

 introduced plants, brought into the country directly or indi- 

 rectly by man. Some such as Dandelion, Yarrow, and prob- 

 ably the common Plantain and the common Purslane, are 

 importations as weeds, although the species naturally occupy 

 some part of the country. 



1 American Journal of Science and Arts, 3 ser., xviii. 161. (1879.) 



