20 



Relations of Geology to Agriculture 



The physiological history of this Lithospermum teaches us 

 both how necessary a certain amount of physiological knowledge, 

 in reference especially to the plants of his own local flora, is to 

 the practical farmer ; and also how unexpectedly the careless 

 farmer may be punished for a neglect of what may be called the 

 very first rule of strong-land farming — that is, of keeping his 

 land clean. On the flat clay lands of Lower Canada, opposite to 

 Montreal, formerly celebrated for their wheat, I found the same 

 weed spoken of as a universal pest, though as in New York State 

 it was said to have been wholly unknown thirty years before. A 

 constant repetition of wheat crops for a long series of years with- 

 out cleaning had led to this result. 



The peculiarities in the character and habit of this weed consist, 

 firsts in the hard shell with which its seed or nut is covered ; 

 second, in the time at which it comes up and ripens its seed ; 

 third, in the superficial way in which its roots spread. The 

 hardness of its covering is such that neither the gizzard of a 

 fowl nor the stomach of an ox can destroy it." Thus it will be 

 for years in the ground without perishing — ready to sprout when 

 an opportunity of germinating occurs. It grows very little in 

 spring, but it shoots up and ripens in autumn, and its roots 

 spread through the surface soil only, and exhaust the food by 

 which the young wheat should be nourished. A knowledge of 

 these facts teaches us, first, that unless care be taken to exclude 

 the seed from the farm it will remain a troublesome weed for 

 many years, even to the industrious, careful, and intelligent culti- 

 vator. It is said to be so prolific as to increase "more than 200 fold 

 annually !" In the secojid place, that spring ploughing will do 

 little good in the way of extirpating it, as at that season it has 

 scarcely begun to grow. United spring and autumn ploughing is 

 " the only reliable remedy." Thirdly — that raising wheat year 

 after year allows it to grow and ripen with the wheat, and to seed 

 the ground more thickly every successive crop. It is said that 

 when it has once got into the land two or three successive crops 

 of wheat will give it entire possession of the soil. It is not there- 

 fore the immediately exhausting effects of successive corn crops 

 which have alone almost banished the wheat culture from large 

 tracts of land in North America, especially on the river St. Law- 

 rence ; the indirect or attendant consequences of this mode of 

 culture — the weeds it fosters, Sec — have had an important in- 

 fluence also. 



These observations are not without their value at home. For 

 although with us a continued succession of corn crops is rarely 

 now seen upon any land, yet foul and weedy farms are unhappily 

 still too frequent. And the more one studies the history and 

 habits of the weeds, which almost every district can boast of as 



