2 PLANT LIFE 



Moisture. — With respect to their water-loving habits plants 

 have been classified into three societies: Xerophytes, or desert 

 plants, such as cactus, sage brush and mesquite. (2) Hydro- 

 phytes, or water-loving plants, as pond lily, cat-tail, water cress, 

 and algae. (3) Mesophytes, or mid-region plants, such as most of 

 our garden, orchard, and farm plants. 



The desert-loving plants have very extended root systems with 

 which to obtain moisture; and have limited leaf surface, and very 

 leathery covering to reduce evaporation. 



Water-loving plants have much more leaf surface than root 

 surface. Some have no true roots. 



The mid-region plants differ widely in their endurance of and 

 requirements for water. The quince, for example, has shallow 

 roots and can be made to grow on ground that is too wet for the 

 peach (Chapter XVI). 



Plant Food Supply. — Plants of the farm, garden, and orchard 

 secure about five per cent of their food from the soil and the other 

 ninety-five per cent from the air. Plants take mineral matter from 

 the soil and organic matter from the air. That taken from the soil 

 limits or controls the growth more than the other. In other words, 

 the soil supply is more limited than the air supply. If the mineral 

 supply is increased the plant can take more organic matter from 

 the air. There is practically no limit to the supply of organic mat- 

 ter which plants can take from the air, except that enough mineral 

 matter must be taken from the soil to keep up the proper ratio of 

 about one to nineteen, to suit the plant. 



If a gardener increases the available plant food in the garden 

 soil the crop, in using that, will also use about nineteen times as 

 much from the air — with no additional cost to the grower. 



The growers problems are: (1) to keep up the supply of plant 

 food in the soil, (2) to make it available, (3) to make the soil con- 

 ditions so favorable that the plant can secure the food, (4) to keep 

 other plants, as weeds, from robbing this food supply from the crop. 



Plants Need Air. — Most of our crop plants need only the oxy- 

 gen and carbon dioxide found in all air, but the legumes, such as 

 clover, peas, and beans, also secure nitrogen either directly or indi- 

 rectly from the air. (Chapter XXIV). Experiments with plants 

 grown without a proper supply of air show conclusively that plants 

 must have- a normal supply of these components of the air. 



HowOxygen and Carbon Dioxide Are Obtained. — All the green- 

 leaf plants breathe air into their leaves and green parts of their 



