SUPPLEMENT 



CHAPTER III. 



PLANTS THAT KNOW HOW TO MEET HARD TlflES. 



The aim of this chapter is to develop the adaptation of plants to a 

 warm, dry climate. Another chapter will deal with plants that spring 

 up under reverse conditions, that is, with plenty of moisture but a 

 limited amount of heat. As some knowledge of the relations between 

 climate and vegetation underlies all intelligent study of geography, 

 this feature of plant study seems especially important. 



The first point to be emphasized is the paramount necessity for 

 water in plant economy. Water itself is a building material ; it 

 enters into all substances that compose a plant ; it is also necessary 

 as a solvent for other building material ; besides this, the transpira- 

 tion current is the main propelling power. If children have not 

 been set to thinking of water in the soil and of evaporation in con- 

 nection with their geography, this should be done now. They usually 

 know that as we dig down we come to moist earth. Perhaps they 

 know that in California stream beds there is often water below the 

 surface. In our narrow canons and on steep north slopes moisture is 

 usually evident. It is easy to show the relations of heat and dry air 

 to evaporation by some common i. lustration, such as the drying of 

 clothes. 



It will be well if the teacher can supervise the collecting of these 

 autumn plants. Happily the plan of spending an occasional half- 

 day in out-of-door study is gaining favor in our schools. In this case 

 half an hour in a vacant lot or field and along the roadside would give 

 an impulse to the collection, but if a visit to a stream-bed or a canon 

 be feasible the lesson will be much more impressive. In the suburbs 

 of Los Angeles, along the Arroyo Seco, all of the plants referred to in 

 the Reader, and many others, could be found in a half-mile walk. In 

 other regions the flora will be somewhat different, but types of dry 

 climate vegetation will be abundant. If there are no native plants of 

 the fleshy type, use the cultivated Sedums (hen-and-chickens, live- 

 forever) or the fleshy plants often used to cover our grounds and 



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