6 THE MONTANA EXPERIMENT STATION. 



enclosures or in streets and lanes, where there is less pasturage. 

 Those found in meadows and pastures are frequently acaulescent 

 (stemless), like the dandelion and plantain, while along streets 

 and highways they are often prostrate, as in the case of pigweed 

 pursley, knotgrass, vervain, carpet weed, and wild tomato, a 

 habit which puts them beyond the reach of most grazing animals. 

 Many have bitter or poisonous secretions or excretions which 

 cause them to be avoided by animals, and others develop spines, 

 prickles or stinging hairs for the same purpose. A considerable 

 number of weeds are able to germinate on and penetrate with 

 their roots the packed soil of street and roadside and to with- 

 stand the excessive dryness of the later summer, when many other 

 plants would die under similar conditions. 



But one of the most remarkable characters of weeds is their 

 wonderful power of reproduction. Many annuals begin blooming 

 almost as soon as they are out of the ground and produce seed 

 until the frosts of autumn, not rarely going through several gen- 

 erations in a single season, while the number of seeds produced by 

 a single plant often mounts up into hundreds of thousands. With 

 most other plants the season is far advanced before they attain 

 maturity, or their period of fruiting is limited to a short season in 

 early spring and the number of seeds produced is relatively small. 

 The seeds of many weeds are also remarkable for their vitality, 

 and are often able to germinate a dozen or more years after being 

 exposed to ordinal soil conditions, and it is this property which 

 renders the sunflower, wild oat, wild mustard, pigweed pursely, 

 wild tomato, tumble-weed and others so difficult to exterminate 

 when they have once become established. A number of species are 

 more or less fleshy so that they are able to take root again after 

 being dug up, or are at least able to mature the seeds already set, 

 and this habit makes them palatable for stock and thus aids in 

 the distribution of their seed. The large fleshy roots of the 

 dandelion and docks are difficult to kill while the underground 

 stems of the wild morning glory, the Canada thistle, sheep-sorrel, 

 milk-weed, wild liquorice, &c, not only spread the parent plant, 

 but are even aided by the processes of cultivation. 



But weeds also labor under certain disadvantages. Nearly all 

 species are desirable food for stock, of which they take advantage 



