588 REPORT OF STATE GEOLOGIST. 



of constant care and intelligent foresight. There is a very grave ques- 

 tion as to whether any so-called "weed laws" will be of much avail 

 so long as there is so little definite knowledge of plants and of the laws 

 governing plant growth. 



A weed may be defined as a plant which contests with man for the 

 possession of the soil. It is more than a "plant out of place;" it is a 

 plant fighting for a place. The great majority of our native plants 

 do not rise to the plane of weeds in the usual acceptation of that term. 

 The list of those which make a constant and vigorous fight against 

 man's supremacy is comparatively short in any given area, and the 

 forms may be easily recognized, their number rarely exceeding twenty 

 or thirty. The habits of life, the methods of seed dissemination, the 

 conditions of germination of these forms should be known by every 

 agriculturist if he hopes for the best results from his labors. 



That a plant may make this semi-successful fight, it must possess 

 certain qualities which give it advantage in the struggle for existence, 

 whether the struggle be against existing plants, browsing animals or 

 man himself. Weeds must be able to adapt themselves to a wide range 

 of merely physical conditions, such as soil character, both as to its 

 chemical composition and physical constitution, to sharp differences 

 in the water content of the soil, and to variations in temperature 

 and light exposure. Very few plants, relatively, have such range, but 

 those that have are weeds, unless by chance man has taken them for 

 his own use as crop or forage plants. A plant to be a crop plant must 

 originally have been capable of adapting itself to this wide range of 

 conditions. It is true that in such plants man has, through cultiva- 

 tion, wrought changes, that as a rule, they now require care for their 

 proper development, but this was simply a matter of exchanging one 

 quality for another. Originally, then, weeds and crop plants were very 

 much alike in this matter of plasticity, and it is little wonder that they 

 come in conflict for the possession of the soil. Any plant, then, hav- 

 ing this power of adaptation possesses one of the essential qualities 

 of a weed. 



The strange plant which the farmer recognizes as growing in rich 

 or poor soil, in dry or moist places, in the shade or in the open sun- 

 light, holding its own in all of these situations, has in it the poten- 

 tialities of a weed, and that which may be the curiosity of to-day may 

 be the pest of to-morrow. A few years ago a plant was sent me which 

 I recognized at once as the Russian thistle. The letter informed me 

 that a single plant had been found growing in a field near the railroad. 

 Suggestion was made that the plant be destroyed before it set seed, 

 but the advice was not followed. The next year two wagon loads of 



