822 WEED FLORA OF IOWA 



He introduces the subject by giving an account of the structure 

 of plants. Throughout this admirable treatise, under the head of 

 observations, Dr. Darlington gives an account of the troublesome 

 weeds. The book describes such weeds as Indian mallow, bladder 

 ketmia, common mallow, quack grass, horse nettle, boot jack, 

 cocklebur, ragweed, dead nettle, smartweeds and European morn- 

 ing-glory. Strangely enough, however, the common morning- 

 glory is not mentioned, nor is the field dodder or the clover dodder. 

 This work passed through another edition revised by Dr. George 

 Thurber, a botanist of some note who was editor for a time of the 

 American Agriculturist and died in 1863. The second edition 

 of the book, under the title of American Weeds and Useful Plants, 

 appeared in 1859. This work filled a splendid place in American 

 agricultural literature and did much to stimulate a study of the 

 weeds which are injurious to agriculture. 



Mr. Thomas Shaw in 1893 published a small book in which he 

 discussed the prevalence of weeds, the evils which arise from the 

 presence of weeds, the possibility of destroying weeds, the agencies 

 concerned in the distribution and propagation of noxious weeds, 

 methods and principles generally applicable in the destruction of 

 weeds and finally specific modes of eradicating certain trouble- 

 some weeds, which should generally be adopted to keep a field free 

 from weeds. He makes many excellent suggestions, among which 

 are the following: 



(1) The persistent and careful study of the habits of growth 

 of all the various sorts of weeds with which one's farm is infested, 

 so as to be able to deal with them in the most rational way possible. 



(2) The modification (when necessary) of the scheme of rota- 

 tion that has been adopted, so that such crops as allow the seeds 

 of the weeds which infest them to ripen, may for a time, be omitted 

 from the rotation. 



(3) When certain methods of eradication have been fixed upon, 

 the careful and wise adaptation of these methods to such condi- 

 tions of soil and climate as are found in the locality concerned. 



(4) The exercise of due care when seeds are purchased, to see 

 that they are perfectly pure, that is, perfectly free from the seeds 

 of weeds; and also the exercise of due care with respect to such 

 seeds as are grown at home to see that they, too, are perfectly free 

 from weed seeds. 



(5) and (6) * * * 



(7) The growing of hoed crops upon the farm infested, to the 

 largest extent that is practicable. 



