The Pines 5 



This genus was probably more abundantly represented in former geologic 

 times than now, as there are numerous representatives known in the fossil remains 

 of the Cretaceous and Miocene formations. Amber is a fossil resin produced by 

 some member of this genus, or of one closely alhed to it. 



The pines have two kinds of leaves, the primary, which soon disappear and 

 are seldom seen except on seedhngs or on vigorous sprouts sometimes growing 

 from stumps or injured trunks; they are deciduous, Hnear, more or less flat or 

 sometimes scale-Hke. The secondary or ordinary foHage-leaves persist for at 

 least two years in fascicles of 2 to 5 or 7, subtended by the bud-scales, and in 

 many species portions of these are united to form a sheath around the base of 

 the fascicle; rarely there is but one leaf; they are stiff-pointed, usually minutely 

 toothed, semicircular or triangular in cross- section; they have stomata on i face 

 or all, and i or 2 fibrovascular bundles. The flowers usually appear in spring, 

 the staminate and pistillate ones mostly in separate clusters (monoecious) or rarely 

 both kinds in the same cluster (androgynous), the staminate usually oval or cy- 

 lindric, composed of many sessile, 2-celled anthers. The pistillate flowers are 

 nearly terminal, or lateral, solitary, in pairs or often in clusters, erect or recurv-ed, 

 sessile or stalked, consisting of many carpellary scales, accompanied by small 

 bracts, spirally arranged and bearing at the base of their inner surface 2 naked 

 inverted ovules. The fruit is a cone, maturing usually at the end of the second 

 season, opening and shedding its seed at maturity, in some species persistent on 

 the branches for many years. The cone-scales are elongated, and variously 

 thickened and appendaged at the exposed apex. The seeds are borne in pairs 

 at the base of the scales, often winged, their coating more or less crustaceous; 

 cotyledons 3 to 15, rarely more. 



The name is the ancient name of a pine tree. The so-called Scotch pine, 

 P. sylvestris L., of Europe, is the type species. 



A. Leaf-sheaths loose, falling away early. 

 Cone-scales without spines. 

 Wing of the seed large; White pines. 



Leaves slender, pale green, eastern tree. i. P. Strobus.- 



Leaves stiff, green; western trees. 



Cones 1.2 to 2.7 dm. long. 2. P. monticolar 



Cones 3 to 4.5 dm. long. 3. P. Lajnbertiana. 



Wing of the seed much shorter than the body. 



Leaves slender; cone-scales reflexed. 4. P. strobiformis. 



Leaves stiff; cone-scales not reflexed. 



Cone-scales brown, spreading, their tips merely pointed. 5. P. f!exilis.-~ 



Cone-scales purple, remaining closed, their tips triangular. 6. P. albicaulis.^ 

 Wing of the round seed minute; Nut pines. 



Leaves slender; bark very scaly. 7. P. cembroides. 



Leaves stout; bark not scaly or but little so. 



Leaves usually in 4's, sometimes 3 or 5; tree of southern 



and Lower California. 8. P. quadrijolia. 



Leaves i to 3 in each fascicle. 



