MISCELLANEOUS PLANTS 299 



inconvenience and expense. We call them weeds. ^ Their domes- 

 tication is not of our choosing but of their own making, and it 

 has come about in any case because their individual require- 

 ments fitted almost perfectly with those of some other species 

 which we were trying to domesticate and produce in quantity. 



For example, chess {Bromus sccalhms) is a plant having the 

 same soil and seasonal requirements as wheat, though of a dis- 

 tinctly different genus. The seeds are near enough alike, how- 

 ever, to be separated with great difficulty ; hence some chess is 

 nearly always sown with wheat. The chess plant is much hardier 

 and much more prolific ^ than the wheat, so that if the two were 

 thrown together, the chess would soon take the ground. 



As it is, if anything happens to the tender wheat, as in winter 

 killing, there is generally enough chess at hand to make a 

 showing, even with less than two hundred spears to the stool, 

 giving rise to the absurd belief that the wheat has ''turned 

 to chess." 



Every weed has some natural advantage, generally arising in 

 the crop conditions with which it most easily and naturally 

 associates, and here is the vulnerable point of attack for its 

 extenuation. 



Weeds, of course, came out of the wild, and most of them 

 -till exist in the wild in the same regions which they infest as 

 weeds. This is true of* such as cocklebur, Canada thistle, 

 f juack grass,^ etc., but others, like cockle and chess, are not found 

 except in association with growing crops ; that is to say, they 

 do not readily escape from cultivation. 



The behavior of a weed upon first introduction is little indi- 



' ation of what its subsequent history will be. Wild lettuce, for 



xample, spread over the western United States a few years 



1 The best definition for a weed is " a plant out of place." 



* The writer once counted two hundred and four species of chess, each 



bearing a full " head " and all springing from a single root originating from a 



single seed. 



' These weeds, however, are not, in most cases, truly wild, but have been 



" introduced " and afterwards have " run wild " like feral animals. 



