SUPPLEMEN7 



moisture in the soil. In the valleys of Southern California the foliage 

 of the sycamores, alders and cottonwoods is practically functionless 

 by October or November, but the leaves do not always fall entirely until 

 after the new ones come in February and March. The alders are in 

 full flower in January. Some willows and the elder are nearly or 

 quite evergreen. The poison oak is leafless for a brief period, but is 

 often in leaf again before January. Introduced deciduous trees take a 

 winter rest, but the leafless period is shorter than in our .Eastern States. 

 Such facts as these can be observed, although a theory fitted to them 

 may not be at hand. Of course giving the name periodicity explains 

 nothing. There is really much of interest in connection with the 

 falling of leaves; the removal of the carbohydrates, and the various 

 alterations in color due to chemical changes that accompany their 

 removal, the fact that the falling of the leaf is a process of excretion, 

 the effect on the soil, etc. Leaves are not broken off leaving a raw 

 surface subject to injury, but a layer of separation, consisting of 

 corky cells that separate easily, is formed, and the leaf scar is water- 

 proof from the first. The buds in the axils of the leaves, or under 

 the petiole in the sycamore, should be noted. In short, everything 

 possible should be done to foster or to cultivate in California children 

 a love for trees. 



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