n6 



WEEDS OF THE FARM AND GARDEN 



weed, morning glory, nimble will, northern nut grass, 

 quack grass, tanweed, western nettle, wild liquorice, wild 

 poppy, wild timothy, woolly thistle, yarrow. 



Other kinds of roots are the aerial, which are produced 

 in the air, an example of this class being the roots of the 

 poison ivy, the brace roots of Indian corn, trumpet 

 creeper, etc. The brace roots of corn become absorbing 

 organs as soon as they strike the ground. In the poison 



ivy, they assist the plant in 

 climbing, taking the place of ten- 

 drils. In one class, including 

 certain orchids, the plants be- 

 come attached to other plants, but 

 do not take any nourishment 

 from them. These are known as 

 epiphytes. In a third class, the 

 roots are not only attached to 

 other plants, but obtain nourish- 

 ment from them. These are 

 called parasitic plants, in which 

 group are the clover dodder and 

 green parasites such as mistletoe. 

 Some roots become greatly thick- 

 ened, such as in the sweet potato, 

 dahlia, carrot and turnip, the up- 

 per part of the turnip, however, 

 being really a stem. Roots of 

 this class store food for future 

 use, and are known as fleshy roots. They are conical, 

 as in the carrot ; fusiform, as in the dahlia ; turnip-shaped, 

 or napiform when like those of the turnip. 



The Stem. The stem occurs in an abbreviated form 

 in the seed; but as we ordinarily see it, it is above the 

 ground. It is spoken of as the ascending axis, and is 

 divided into nodes and internodes, the leaves making 

 their appearance at the nodes. In addition to the stems 



Fig. 38. An annual weed, 

 wild buckwheat (Poly- 

 ffonum Convolvulus). 



