178 NATURE STUDY AND AGRICULTURE 



make them successful. If possible, have them record 

 whether the weeds are annuals, biennials, or perennials. 

 If these terms are new, there is no better place to explain 

 and illustrate this grouping of plants. Annuals are those 

 plants which grow from seed to seed each year, and die 

 away completely in the winter. Biennials require two years 

 to grow from seed to seed. Many common weeds are both 

 annual and biennial in habit. Those plants which persist 

 from season to season, indefinitely, by rootstock, or other- 

 wise, are called perennials. 



Throw out hints occasionally that will keep up the 

 interest. How many seeds are you carrying around and 

 sowing when a burdock bur is fastened to your- clothing ? 

 Why do you find some burdock plants growing in a green 

 rosette close to the ground, while others have tall stems 

 with small leaves and many burs ? What other weeds do 

 you find that show these same characteristics? Thistle, 

 wild parsnip, wild carrot, and mullein are familiar examples 

 of biennials. 



Who knows how many seeds in one cocklebur? If 

 some of you find milkweed growing in a cornfield, dig 

 down and see if you can discover the secret as to why this 

 weed is hard to kill out when it gets a start. Try the wild 

 morning-glory in the same way. Why are dandelions and 

 plantain successful lawn weeds? 



It will add much to the interest of weed study to have 

 the children make a collection of weed seeds; also of the 

 stems and leaves, where it is not practicable to bring in an 

 entire plant. The latter may be pressed and mounted. 

 The seeds may be placed in envelopes or bottles. Small 

 vials may be purchased at little expense, or brought from 



