296 THE CULTIVATED EVERGREENS 



The number of the fibro- vascular bundles and the position of the resin-ducts 

 can be readily seen with a common magnifying glass in thin cross-sections 

 made with a sharp razor from the middle of the leaf and placed on a glass 

 plate. The shoot which develops in spring from the terminal winter-bud 

 (spring-shoot) produces in most species only one internode with one whorl 

 of branchlets and is therefore called uninodal and bears the cones at the end 

 of the shoot (subterminal), while in other species the spring-shoot produces 

 two or more often incomplete whorls of branchlets (multinodal shoots) 

 and bears the cones partly in the middle of the shoot (lateral); occasionally 

 summer-shoots appear on uninodal shoots and change it thus to an incom- 

 pletely multinodal branchlet. (Pinus is the old Latin name of the pine-tree.) — 

 The genus contains about 70 species distributed throughout the northern 

 hemisphere from the arctic circle to Mexico and the West Indies, North 

 Africa, and the Malayan Archipelago; in the tropical and subtropical regions 

 they are confined to the mountains. 



Pinus is the largest and at the same time the most important of all 

 the coniferous genera. In the colder and temperate regions it furnishes not 

 only the most important timber trees, but also the most valuable evergreen 

 plant material for permanent and larger plantations, as the more valuable 

 pines, unlike most spruces and firs, do not lose their beauty with age, but gain 

 in character and picturesque appearance. 



KEY TO THE SPECIES BASED CHIEFLY ON CONE-CHARACTERS 



A. Bracts subtending the leaf -fascicle not decurrent; sheath of fas- 

 cicle deciduous; leaf with one fibro- vascular bundle (Hap- 

 loxylon). 

 B. Scales with terminal umbo. 



c. Seeds wingless or with rudimentary wing. 

 D. Margin of leaves serrulate. 



E. Branchlets pubescent or tomentose : cones indehiscent. 



F. Cones cylindric-conical : branchlets pubescent. ... 1. P. koraiensis 



FF. Cones ovoid : branchlets brownish-tomentose 2. P. Cembra 



EE. Branchlets glabrous: cones dehiscent, cylindric- 

 conical 5. P. Armandi 



DD. Margin of leaves entire. 



E. Cones indehiscent 3. P. alhicaulis 



EE. Cones dehiscent 4. P. flexilis 



CO. Seeds winged, with long wing (rather short in No. 8). 

 D. Length of cones 10-18 inches: branchlets pubescent. 

 E. Cone-scales with elongated and recurved apex: 



leaves slender 6. P. Ayacahuite 



EE. Cone-scales rounded : leaves stout 7. P. Lambertiana 



DD. Length of cones less than 10 inches. 

 E. Cone-scales with convex thickening. 



F. Cone about 2 inches long, ovoid: branchlets pu- 

 bescent 8. P. parviflora 



