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H THE PINE FAMILY— PINACEAE. 



There is general agreement that the Pine and Yew families com- 

 prise the two divergent branches of the conifers which differ from 

 each other in morphological characters and geographical distribu- 

 tion. The conifers comprise 34 genera and about 300 species, of 

 which number 8 genera with 71 species belong to the Yew family 

 (Taxaceae) and 26 genera with 226 species to the Pine family 

 (Pinaceae). The representatives of these two families are found 

 mainly in temperate regions, both northern where the genus Pinus 

 predominates, and southern where the genus Podocarpus predomi- 

 nates. The geographical distribution of these two families is pecu- 

 liar since the genera of the northern temperate region are not found 

 in the southern and those of the southern are not found in the 

 northern, excepting the two genera (Heyderia and Podocarpus) 

 which cross the tropics. Geological records together with the sim- 

 plicity of floral structure show us that the members of this family are 

 amongst the oldest living representatives of the ancient arbores- 

 cent type of vegetation. Morphological evidence seems to point 

 to the belief that the Yew family contains representatives of the 

 most primitive form of conifers and that the genus Pinus in the 

 Pine family contains the most highly specialized forms. The sole 

 representative in Pennsylvania of the family Taxaceae is the Ameri- 

 can Yew or Ground Hemlock (Taxus canadensis, Marsh.) It is a 

 small evergreen shrub seldom exceeding 5 feet in height. 



The Pine family is of especial economic value on account of the 

 many commercial products which are obtained from it and the wide 

 range of silvicultural characteristics which its members possess. 

 The annual wood production of the members of this family in the 

 United States far surpasses that of the members of any other fam- 

 ily. The wood differs markedly from that of the broad-leaved trees 

 in its greater uniformity, smaller porosity, and less conspicuous 

 medullary rays. Some members of this family yield large quantities 

 of resin, tar, turpentine, and pitch. The fruit of some species is 

 often of considerable importance as food, and the bark of many 

 species is used in the process of tanning. 



The members of the Pine family have awl-shaped, scale-shaped, 

 or needle-shaped entire leaves, which are usually persistent. The 

 American Larch is the only coniferous species native to Pennsylva- 



ii 



