A STUDY OF AUTUMN WEEDS 29 



enlarged, to show different devices for wind carriage. Examine the fruits 

 of the sour or curly dock and draw one enlarged. Can you think how the 

 corky rim of this seed would serve in carrying it to new locations ? Draw 

 a bur of the cocklebur. How are such seeds carried ? List some other 

 weeds whose fruits are carried in a similar way. Of the two seeds in a bur 

 of the cocklebur, one germinates the first spring after production, the other 

 not until the second spring. How would this be advantageous ? Touch 

 the ripe pods of the wild balsam. What happens ? Find out how the wild 

 cucumber spreads its seeds. (Read Lubbock's Flowers, Fruits and Seeds, 

 pp. 52-66.) Many weed seeds are eaten by birds, and some of them are so 

 hard-shelled that they pass through the digestive tract unharmed. Most 

 of them are digested, however. If the seeds or fruits are poisonous, would 

 it be advantageous to the plant ? Find some figures to show how many 

 weed seeds are eaten by birds. See report from Yearbook, Department of 

 Agriculture, S. H. Judd, " Birds as Weed Destroyers." Enter on the 

 opposite page some of the facts given in this report. 



Other methods of propagation. Weeds reproduce also by other means 

 than seeds. Many have underground stems that run along under the sur- 

 face and send up new shoots at intervals. When these underground stems 

 are cut in pieces by plowing or spading, each piece may produce a new plant. 

 List some that have this habit. Many weeds send out runners that strike 

 root at their tip; name some. Some have prostrate or decumbent stems 

 that strike root at each node; name some of these. Suppose such weeds 

 were tramped upon by cattle, broken into pieces by their sharp hoofs, and 

 at the same time pressed into the ground, how would it profit the plant ? 

 Name some pasture plants that behave so. 



Protection. What weeds have some very adequate means of protec- 

 tion? Name some that have specific devices for keeping warm. 



The following weeds are protected from browsing animals as indicated : 



is protected by stiff hair. 



is protected by disagreeable taste. 



is protected by irritating juices. 



is protected by thorns on its stems. 



is protected by prickers on its leaves. 



has fruit covered by prickers. 



