SUPPLEMENT 



CHAPTER XIV. 



PLANT FAfllLIES. PART II. EXOGENS OR 

 DICOTYLEDONS. 



The characteristics of Dicotyledons have already been indicated in 

 Chapters II and XIII, and the structure of perennial exogenous 

 stems has been given in the Supplement to Chapter VIII. There is 

 little observation work with new plants suggested in this Chapter, its 

 aim being mainly to review systematically plants already studied, 

 and to aid in Geography work. 



The members of group I come under the Apetalae, if this division is 

 made. Many of the native trees of the group have been already con- 

 sidered in Chapter VIII and its Supplement. The willow belongs to 

 the Northern Hemisphere, and extends well up into arctic regions. 

 The two species of Populus that grow along our streams, P. tricho- 

 carpa, Torr., and P. Fremonti, Wats., are indiscriminately called 

 cottonwood, or poplar; the mountain species, P. tremuloides, is 

 known as aspen. Our fine park or field live oak, the Spanish encino, 

 which is common near the coast, is Quercus agrifolia, Nee. ; near 

 Los Angeles this is interspersed with O. Engelmanni, Greene. Q. 

 chrysolepis, Liebm., of the mountains sometimes attains immense size; 

 the noble white oak, or Roble, Q. Lobata, Nee., with its deciduous 

 lobed leaves, is found in fertile valleys, especially northward; Q. den- 

 siflora, H. & A., the chestnut oak, or tan bark oak, has bark so valu- 

 able for tanning leather that the species seems doomed to extinction. 

 Oaks throughout the North Temperate zone are prized as ornamental 

 and timber trees; several species are valued for tanning; the cork oak 

 of Mediterranean regions is sometimes seen in cultivation in Cali- 

 fornia. While the walnut of the old world can be very profitably 

 cultivated in parts of California, the native walnut does not compare 

 in size with that of our Eastern States. There are several other 

 members of this group much prized for their nuts and wood which 

 are common in the Eastern States but do not thrive here; the chest- 



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