WEEDS 177 



beggar ticks, etc. Some seeds enclosed in the pulp of fruit 

 are eaten and dispersed by birds. Examples of such plants 

 are the poison ivy, and pokeberry and some of the night- 

 shades, such as the ground cherry. Some weeds produce seeds 

 that are light and almost impervious to water. During rains 

 these seeds are carried about by the water and left at the 

 edges of streams or on flooded land after the water has sub- 

 sided. Some weed seeds, because of a similarity in size, are 

 difficult to separate from the seeds of cultivated plants such 

 as clover, timothy, etc., when they are threshed. For this 

 reason the weed seeds may be planted along with the seeds 

 of the crop to be produced. 



Means of control of weeds. There seems to be no practi- 

 cal way of entirely controlling weeds, but their effect on 

 crops may be considerably reduced. 



First in importance is clean culture. This means killing 

 the weed seedlings as fast as they appear during the growing 

 season. It is possible to do this when some cultivated crop, 

 such as corn or potatoes, is produced. In discussing con- 

 servation of soil moisture, much emphasis was placed upon 

 the need of frequent cultivation so as to maintain a good 

 mulch. Indeed, recent experiments in Nebraska, Illinois, 

 Ohio, Minnesota, Michigan, and by the U. S. Department of 

 Agriculture seem to indicate that keeping the soil free from 

 weeds is even more important in conserving moisture than 

 using soil mulch. In farm practice keeping down weeds and 

 making a soil mulch are usually done by the same operation. 

 In an ordinary season when the rainfall is well distributed 

 and not excessive, maintaining a good mulch will, at the 

 same time, effectively control the weeds. In rainy seasons 

 especial attention must be given to the removal of weeds. 

 Uncultivated crops, such as wheat, should be grown in short 



