42 THE BOOK OF ALFALFA 



recleaning; consequently, they are often sown along* with 

 the alfalfa seed, especially in that which has been im- 

 ported. If a field is badly infested, it should be plowed up 

 and devoted to some other crop for a few years. Prof. 

 F. H. Hillman of Nevada, (BuL No. 47) says there are 

 several kinds that infest alfalfa, but two kinds are espe- 

 cially common and destructive in this country. Cuscuta 

 epithymum is apparently the commoner. "The seeds 

 of this are very small, and are almost sure to escape 

 detection on casual examination of the samples ; yet, once 

 recognized under the lens, their presence may be easily 

 discovered. They are so much smaller than alfalfa seeds 

 that the use of a sieve of twenty meshes per inch separates 

 them from the latter when only free dodder seeds are 

 present Not only are various other small weed seeds 

 disposed of in the process, but little if any alfalfa seed 

 worth buying is lost. The few ripened flowers of dodder 

 retaining matured seeds, which sometimes pass the 

 thresher uninjured, may be removed by proper fanning. 

 It is safe to say that no purchaser of alfalfa seed can 

 afford to neglect sifting his seed carefully with a twenty- 

 mesh sieve, which is the mesh the writer recommends for 

 the separation of this kind of dodder from alfalfa seed. 



'^Cuscufa arvensis is another dodder as destructive, 

 when once established. Its seeds seem to be less common, 

 however. They are larger than the preceding, many of 

 them being practically the same size as the smaller, more 

 rounded alfalfa seeds, which they often strikingly resem- 

 ble. Thus they are hard to detect, and cannot be 

 removed without the loss of much small alfalfa seed. 

 This should be the more dreaded of the two dodders. 



