68 



uia which is without foliage in winter. The subjoined key gives 

 the characteristics of the genera commonly found in Pennsvlvania: 



KEY TO THE GENERA. 



Page. 

 1. Fruit a dry cone with winged seeds 2 



1. Fruit a flesby, round, dark-colored lierry with bony seeds, Juniperus ST 



2. Leaves linear to needle-shaped, not closely overlapping; cone-scales numerous; buds 



scaly • 3 



2. Leaves scale-like, closely overlapping; cone-scales few; buds not scaly 7 



3. Leaves in bundles of two or more except on young seedlings and on terminal twigs 



of Larix, * 



3. Leaves solitary, 5 



4. Leaves persistent, 2-5 in each bundle ' Pinus 6S 



4. Leaves deciduous, more than 5 in each cluster, Larix 77 



5. Leaves flattened, whitish on lower surface 6 



5. Leaves 4-angled, needle shaped Picea 78 



6. Leaves with leaf-like stalks, about 2/5 of an inch long; twigs rough; cones small 



with persisteut scales Tsuga 83 



6. Leaves without leaf-stalks, usually 4/5 of iin inch or more in length; twigs smooth; 



cones large with deciduous scales, Abies S4 



7. Leaves le-ss than I of an inch long; twigs rattier .-slenrtcr. not prominently flattened; 



cones globular with shield-shaped scales which do not overlap Chamaecyparis 85 



7 Leaves i of an inch or more in length; twigs rathijr prominently flattened; cones 



elongated with 8 12 overlapping scales Thuja 8S 



THE PINES— PTXUS (Tourn.) L. 



This genus comprises more species than any other belonging to 

 the Pine family. About 70 species are known in the world, 34 of 

 which are found in North America and 6 in Pennsylvania. Of the 

 ?,i species in North America, 13 are found in the eastern part and 

 21 in the western part. Besides the native Pines a number of exotic 

 species have been iilanted extensively for ornamental, and locally 

 for forestry purposes. The commonest exotic species are Scotch 

 Pine (Pinus sylvestris. L.") and Austrian Pine (Pinus Laricio var. 

 austriaca, End].). 



The Pines are adapted to a wide range of climate and soil. Cer- 

 tain species may be found bordering streams and lakes or close to 

 the ocean front while others are confined to mountain tops where 

 they ascend to the timber line. This adaptability makes some of 

 the species of considerable economic value even though they may 

 I)rocluce no wood of commercial importance. They can lie u.sed for 

 afforesting mountain slopes where protection forests are to be formed 

 and maintained, and to reclaim sand barrens. 



The Pines are generally trees, rarely shrubs, and of considerable 

 commercial importance on account of the excellent quality and large 

 quantity of major and minor forest products which 'they yield. Sev- 

 eral species of Pine have always been foremost in the estimation of 



