i88 9 .] 



BOTANICAL GAZETTE. 



71 



but is a vile pest moving northward and eastward, and if not 

 checked in its course will bring dismav to thousands of far- 

 mers who now know nothing of its pernicious habits. 



The interested reader can quickly select from the table 

 the species which are most prevalent over the whole United 

 States, but the relative injuriousness, which is obtained by 

 dividing the denominator by the numerator, is not so easily 

 seen. The following list of 20 is therefore given in the order 

 of injuriousness, beginning with the worst: 



Cnicus arvensis. 

 Agropyrum repens. 

 Xanthium Canadense. 

 Cenchrns tribuloides. 

 Pinicum sanguinale. 

 Ambrosia artemisirefolia. 

 Xanthium stramonium. 

 Ruraex Acetosella. 

 Amarantus retroflexus. 

 Ambrosia trifida. 



Setaria glauca. 

 Chenopodium album. 

 Chrysanthemum Leucanthemum 

 Portulaca oleracea. 

 Rumex crispus. 

 Panicum Ous-galli. 

 Convolvulus sepium. 

 Oapsella Bursa-pastoris. 

 Cnicus lanceolatus. 

 Arctium Lappa. 



The writer is anxious to add to the number of his reports, 

 and will be pleased to hear not only from everv state and 

 territory in the Union, but in such numbers that the sum- 

 mary derived from them may furnish a basis for future cal- 

 culations, if not for national legislation. Questions of erad- 

 ication, quarantine and the like, come naturally after the 

 nature of the pests has been settled upon in the broadest 

 sense. The greater part of this work must be done bv local 

 observers who are willing to aid in arming ourselves as a 

 nation against a vast array of active enemies to American 

 agriculture. If any one will add to or take from the list of 

 34 species herein given, let him do so as a bit of public ser- 

 vice. 



JVew Brunswick* N. *T. 



Sweet Cassava (Jatropha Manihot.) 



II. W. WILEY. 



About the middle of March, last year, I received from 

 Mr. R. II. Burr, of Bartow, Fla., a package of cassava 

 roots. These roots reached the department in fine condi- 

 tion, being apparently as fresh as the day they were taken 



