466 



WATER SUPPLY AND SEWAGE DISPOSAL 



abundance or scarcity of moisture is a large factor determining 

 the character of plant life in any region. Different plants 

 require different amounts of moisture. Certain plants, such 

 as water lilies, reeds, cat-tails, eel grass, bulrushes, wild rice, 

 sedges, and many grasses live and thrive only when growing 

 in shallow ponds or swamps or marshes. Such plants are said 

 to be water plants, or HYDROPHYTES (hydrophyte meaning water 

 plant) . 



At the opposite extreme are plants which live and thrive only 

 when growing in extremely dry soil in regions of scant rainfall. 

 The southwestern portion of the United States, western Texas, 

 New Mexico, Arizona, and southeastern California, is such a 

 region. Here the various forms of the cactus, the yucca, sage 

 brush, and a few other forms of plant life live and thrive 

 although only a scanty amount of moisture is available. Such 



plants are called XERO- 

 PHYTES (xerophyte meaning 

 dry plant). 



Most of the common 

 plant life of the United 

 States, and especially our 

 common cultivated crops 

 require a medium amount 

 of moisture. Our common 

 forest trees, the grasses of 

 our meadows, our corn, 

 oats, wheat, and other 

 grains, potatoes, beans, 



peas, and all the rest of our common field and garden plants 

 thrive best where a moderate amount of moisture is availa- 

 ble. Such plants are called MESOPHYTES (mesophytes meaning 

 middle plants). 



548. How Plants Absorb Soil Moisture. Plants requiring 

 but little moisture, xerophytes, and plants requiring a medium 

 amount of moisture, mesophytes, obtain their supply of mois- 

 ture principally by absorbing the film moisture from the soil. 



FIG. 284. Root hairs on corn roots 

 and on roots of wheat. The soil is still 

 clinging to the wheat root hairs. 



