176 Report of the Department of Botany of the 



Curled dock. — The seed of this common weed occurred in 11 

 per ct. of the samples of alfalfa and in 70 per ct. of the red clover 

 samples. The statement that this weed is introduced by the use 

 of impure seed is borne out by the presence of the seed in so many 

 of the samples examined. 



Russian thistle. — Nearly 1 5 per ct. of the alfalfa samples con- 

 tained seeds of this weed. In addition to its occurrence in seed 

 samples, specimens of the plant have been sent in for identifica- 

 tion, and upon investigation as to the behavior of this weed in 

 the alfalfa fields of the State it was found that in no case did it 

 appear after the first year following seeding. Apparently, it is 

 very susceptible to frost and when it starts in late summer with 

 the alfalfa seeding the plants are destroyed before they produce 

 seed. It is, therefore, considered to be a weed of no great impor- 

 tance in the alfalfa field. 



Roquette. — Of the 614 samples of alfalfa, 28 contained seed 

 of this weed, and several specimens of the plant were sent in for 

 identification. An investigation of each occurrence of the weed 

 revealed the fact that, like Russian thistle, it did not appear after 

 the first year, and is not to be feared by alfalfa growers; but it 

 should not be allowed to ripen its seeds in cultivated crops. The 

 plant is a hairy annual, which resembles wild mustard, and is 

 easily identified by its yellowish-white, aromatic flowers which are 

 netted with dark purple veins. Its flavor is very bitter and 

 pungent, or radish-like. 



Johnson grass. — The seed of this grass occurred in 14 alfalfa 

 and in 3 red clover samples. In addition to its occurrence in 

 seed samples, some inquiries as to its probable importance have 

 been received. It has not been met with in alfalfa fields as yet, 

 and no specimens have been received for identification. 



Yellow trefoil; black medick. — The seed of this plant was 

 found in 12 samples of alfalfa, and in 16 per ct. of the red clover 

 samples, and also in 40 per ct. of the samples of alsike clover. 

 The presence of this seed in such a large percentage of the alsike 

 clover samples is probably due to natural infestation in the field; 



