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THE GUIDE TO NATURE. 



Examine the root systems first. Deep 

 rooting is common to many of the plants 

 that are near enough water to reach it 

 in that way. Sometimes you happen 

 on a ledge that has been laid bare by 

 the action of the weather and are sur- 



THE BARREL CACTUS. 



prised to find massive networks of roots 

 supporting a comparatively small growth 

 above ground. This deep rooting sys- 

 tem is characteristic of the mesquite. A 

 bit of holly no more than eighteen inches 



high will often be attached to a set of 

 roots as many feet long. Other plants, 

 like the wild gourd, have storage reser- 

 voirs in the form of thickened roots, and 

 it is no uncommon sight to see this plant 

 green and flourishing long after every- 

 thing else has succumbed to the burning 

 heat. Deep rooting is by no means the 

 rule with desert plants. In some places 

 no amount of delving downward would 

 reach water. The ground is as dry as a 

 proverbial powder house year in and 

 year out with the exception of brief 

 periods that bring occasional wettings 

 to the upper layers. Hence many plants 

 like the "cat's claw" acacia and the chol- 

 la cactus have what is called a double 

 rooting system. The surface roots then 

 perform the important function of gath- 

 ering the little moisture that does come 

 their way. 



( )nce above ground every care is ex- 

 ercised to guard against unnecessary 

 evaporation. The geometrical form as- 

 sumed by the characteristic desert plants 

 presents the very least surface possi- 

 ble. Nearly ' everything is round or 

 globular. There are few, if any, wide 

 spreading, leafy trees in this sun parched 

 country. Again most desert plants do 

 away with leaves as much as they can ; 

 in fact, some dispense with them alto- 

 gether. The cactus has thorns ; the aca- 

 cia has the phyllodia which stands ver- 

 tically ; others again have leaves at the 

 brief blossom period, but discard them 

 afterwards to stand like bare, thorny 

 poles the remainder of the year. It has 

 been estimated that the ordinary cactus 

 exposes only one-thirteenth of its sur- 

 face, while the coffee, another tropical 

 plant, about seven hundred times as 

 much surface in proportion. If, how- 

 ever, plants do see fit to keep their leaves 

 they shell-lac them over with a shiny, 

 resinous varnish like the creosote bush 

 or cover themselves with hair like the 

 "old man" cactus. The long seasons of 

 drought compel each plant to resort to 

 safe "methods of conserving their water 

 supplies. Each plant maintains some 

 kind of a storage reservoir. If not a 

 deep or thickened root system, then the 

 thickened stem and leaf. The average 

 cactus is with its thickened stem and 

 leaves over ninety-five per cent, water. 



