270 L. H. Pammel. 



weed (Ambrosia artemisiaefoUa), Large Ragweed (Ambrosia trifida), 

 Foxtail (Setaria glauea and 8. viridis) from southern Iowa, Bracted 

 Plantain (Plantago aristata), Nimblewill (Mulilenhergia mexicana), 

 occasionally some Buckhorn (Plantago lanceolata), Carrot (Daucus 

 carota). So far as I know very little Canada Thistle (Cirsium 

 arvense) seed occurs in clover seed grown in Iowa. The Thistle plant 

 does not seed as freely in this state as in the East, Canada, and 

 Europe. 



I do not apprehend so much difficulty in the establishment of 

 Standards of purity because cleaning is a mechanical process, and 

 many seeds can be separated from clover provided the clover is 

 grown in clean fields. More attention miist be paid to the matter 

 of clean fields in our agricultural practice. When it comes to the 

 establishment of Standards of vitality the question is a vere different 

 one. The vitality of seeds varies with the season. This is well shown 

 in such a cereal as maize, which varies greatly in different seasons. 

 There are wide fluctuations in regard to the vitality of maize, depen- 

 ding on the aniount of moisture during the ripening season, and the 

 amount of precipitation in the fall when seed maize is gathered. 



The conditions under which seeds germinate have by no means 

 been determined. The writer and Miss King') have made a study 

 of the germination of a large number of weed seeds. One of the 

 striking facts brought out in this study is the vitality Variation in 

 different seasons. 



Some more rapid method of determining the amount of impurity 

 in samples of seed submitted to analysis should be made. For the 

 purpose of facilitating the work the following method has been devised. 

 I am under obligations to Miss Charlotte M. King for the deter- 

 mination of the weights of weed seeds. This method was published 

 in a former publication ^). 



*) A paper on this subject will be published in füll in the Proceedings 

 of the Iowa Academy of Science for 1910. A brief resume was given at the 

 Winnipeg meeting of the British Association for the Advancement of Science 1909. 



See also Beal, Proc. Soc. Prom. Agr. Sei. 1899, and Waldron, Bull. 

 N. Dak. Agr. Exp. Sta. 62, and the references in Detmer, On germination of seeds. 

 -) L. H. Pammel, R. E. Buchanan and Charlotte M. King in Bull. 

 Iowa State Expt. Sta. 88 : 58. 



The analysis given in another buUetin „Results of Seed Investigation 

 for 1907" by L. H. Pammel and* Charlotte M. King, indicates the value of 

 this method. See*Bull. Iowa State College Expt. Sta. 99 : 71. 



