16 Bulletin 194 



SUMMER KEY TO THE GENERA 



a. Leaves simple. 



b. Leaves needle-shaped, awl-shaped, strap-shaped or scale-like. 

 c. Leaves in clusters of 2-many. 



d. Leaves in clusters of 2-5 sheathed, persistent for several 



years Pinus, p. 25. 



dd. Leaves in fascicles of 8-many, on short, lateral branch- 

 lets, deciduous in autumn Larix, p. 35. 



cc. Leaves solitary, not clustered. 

 d. Leaves opposite. 



c. Twigs flattened; leaves all of one kind, scale-like, de- 

 current on the stem ; fruit a small, pale brown cone. 



Thuja, p. 51. 

 ce. Twigs essentially terete ; leaves of two kinds, either 

 scale-like, or else awl-shaped, often both kinds on the 

 same branch, not decurrent on the stem ; fruit berry- 

 like, bluish Junlperus, p. 53. 



dd. Leaves alternate or spirally-whorled. 

 e. Leaves flattened, soft to the touch. 

 /. Leaves 3^-1^4 inches long, sessile, aromatic; cones 

 2-4 inches long; bark of trunk with raised blisters 



containing resin Abies, p. 47. 



//. Leaves seldom over ^ inch long, short-petioled, not 

 aromatic; cones about ^ inch long; bark of trunk 



without raised blisters Tsuga, p. 49. 



ce. Leaves 4-sided, harsh to the touch Picea, p. 2)7. 



bb. Leaves broad and flat. 



c. Leaves alternate or clustered, never opposite. 



d. Margin of leaves entire or only slightly undulate. 

 c. Leaves 2-5 inches long ; fruit a drupe or berry, 



Nyssa, p. 183. 

 cc. Leaves 5-9 inches long; fruit an acorn. . Quercus, p. 112. 

 dd. Margin of leaves serrate, toothed or lobed. 

 c. Margin of leaves serrate to toothed. 



/. Branches armed with stiff, sharp thorns, 



Crataegus, p. 147. 



