EXERCISE 115 

 STUDY OF A COMMON WEED 



Materials. Any of the common weeds of the vicinity. These 

 should be studied principally in the field. 



Directions for work. Examine a weed with the object of 

 determining what characteristics of the plant enable it to be 

 a weed. 



1. Ability to maintain itself where present, especially if a 

 perennial plant : such qualifications as deep, tough root system ; 

 underground stems ; tolerance of shade, drought, excessive water, 

 and dust ; ability to grow in poor soil ; rapid growth ; disagree- 

 able taste, prickles, etc. 



2. Ability to reach and take possession of new locations : 

 such qualifications as excellent means of seed dispersal ; persist- 

 ent seeds, not easily injured ; rapid-growing seedlings ; early 

 germination ; spreading rhizomes. 



3. Character of injury done : competition with crops by shad- 

 ing ; removal of moisture needed for crops, especially in arid 

 regions ; parasitism on crop plants ; acting as host for insects 

 or fungi injurious to crops, or harboring such insects or fungi ; 

 poisonous effects on domestic animals ; other injuries to animals 

 or animal products; other important facts characteristic of the 

 weed studied. 



4. Means of eradication and prevention. 



References 



BERGEN and CALDWELL. Practical Botany, chap. xxv. 

 BERGEN and CALDWELL. Introduction to Botany, chap. xx. 



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