SUPPLEMENT 



course, transpire very slowly, and it is for this reason that they can be 

 retained during the winter in cold climates. 



The cactus is a type of plant particularly well adapted to regions of 

 long drought for it can remain dormant without losing its parts, 

 above ground. Its roots do not go deep but they are many and long ; 

 so during the rainy season the plant can take in water very rapidly, 

 make its periodical growth, and store enough in its aqueous tissue to 

 balance all the evaporation that can occur through its restricted 

 surface during the drought. The plants sometimes look thin and 

 starved at the end of the dry season, but they usually survive. A full 

 study of the cactus is deferred until it is in flower, when the most 

 common species, the tuna cactus, will have true leaves also. Century 

 plants and Yuccas are of the same type as the cactus, and so are many 

 other desert and seaside plants. Introduced plants of the fleshy type 

 usually flourish in our climate. The Russian thistle is an apalling 

 example of this fact in some parts of the state. It should be 

 remarked that the salts dissolved in the cell contents of some of these 

 plants do much in checking transpiration. 



The "wild broom," (Uosackia glabra or Lotus glaber) comes near 

 being a "switch plant." Switch plants, like most Cacti, reduce 

 transpiration by dispensing with leaves, and carry on food-making in 

 the green cells of the stems, but they have numerous slender, woody 

 stems as the name implies. They abound in many desert regions. 

 One plant of this type, Lepidospartum squamatum, a strong-scented 

 Composite, is common in the sand washes of Southern California. 

 Its summer leaves are mere scales, but soon after the rains, it puts out 

 ordinary foliage leaves of considerable size. 



The Eriogonums, too, are plants that belong to arid regions; 

 they are found only in Western America. The one pictured, E. 

 elongatum, is common and typical. In Southern California a still 

 more common one is E.fasdculatum, a valuable bee plant, commonly 

 known as wild buckwheat. It begins flowering in the early summer, 

 and will be referred to in Chapter XV. Unlike most Eriogonums, 

 this one has many leaves, but they are hard and small, and, as the 

 name implies, fascicled. They are of a type rather common in arid 

 regions, more common in regions of excessive moisture, and particu- 

 larly so in regions where these conditions exist in alternation. They 

 are called rolled leaves because the margins of the leaf roll back so 

 as to leave little of the under surface, i. e., the stomata-bearing sur- 

 face, exposed ; the under surface is further protected by felted hairs. 



In any part of the state a large number of the plants of this autumn 

 collection will belong to the family Compositse, a family children 



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