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_ 
a 
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N 
oo 
EXPLANATION OF PLATES XX-XXIIT. 
Fic. 1.—Pinus Strobus, 3 years old. 
Fic. 2.—Pinus Strobus, 4 years old. 
Isa 
Fic. 6.—Pinus Strobus, 3 vias old. 
Fic. 7.—Pinus virginiana. 
Fic. 8.—Pinus Strobus. 
Fic. 9.—Pinus monophylla. 
Fic. 10.—Pinus excelsa. 
Fic. 11.—Pinus Sir obus, 3 years old. 
Fic. 12.—Pinus silvestri 
Fic. 13 erase Jeffreyi. 
