AUTUMN PLANTS 



like pores can open and close ; when the air is very dry 

 they close and so help the plant, for it is of course when 

 the air is hot and dry that the plants are in greatest danger. 

 Still all these devices do not entirely prevent evaporation. 

 It would be bad for the plants if they did; for if the current 

 of water from roots to leaves were to stop, there would be 

 no raw material brought from the soil to the leaves, and 

 food-making would soon come to an end. So even hard 

 leaves, like the live oak and Eucalyptus give off so much 

 water that in our experiments we can see and weigh it. 

 We use only a few leaves in our experiments; think how 

 much water a great oak or a tall Eucalyptus must give off 

 from all its leaves on a hot summer day ! 



The live oak, even in Southern California, will grow a 

 long distance from streams, but it has many roots, some of 

 which go far and deep in their search for moist soil. So 

 the oak does not rest entirely during the summer, but keeps 

 busy enough to ripen its acorns. The Eucalyptus lives 

 much faster. It sends out new leaves all summer long, 

 even when it grows in places too dry for the live oak to 

 live at all. Its home is Australia, and it seems to have 

 learned there how to defy drought. You know what 

 greedy roots it has ; how they drink in all the moisture 

 from the ground so that other plants that try to live near it 

 starve. You have noticed how little shade the leaves cast 

 at noon. This is because they have their edges toward the 

 sky, and the sun cannot strike their surfaces during the 

 hottest part of the day, and so draw out more moisture than 

 they can spare. Earlier and later in the day the sun shines 

 directly on the blades, and helps them to make their food 

 rapidly. Other trees that have been brought from foreign 

 countries to California, because they know how to stand 

 dry weather, have this same habit of vertical leaves. Find 

 out some of them yourselves. Our own Manzanita, too, 

 has this habit. 



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