SPRUCE AND BALSAM EIR TREES. 3 



red bodies of similar form, from three- fourths inch to about 1 ', 

 inches in length by one-fourth to nearly three-fourths inch in diam- 

 eter. The cones, matured in one season, are cylindrical or egg- 

 shaped, always pendant or bent downward (Pis. I to V). Most 

 of the spruces bear their cones at the extreme top of the crown; 

 some bear cones on branches of the upper half of the crown. As a 

 rule, the cones are only lightly attached to the twigs, and after shed- 

 ding their seed, in early or late autumn, they either fall from the 

 trees during the winter or by spring. The cones of a few spruces are 

 firmly attached and remain on the branches for a number of years 

 after their seeds are shed. The scales of spruce cones are thin and 

 without prickles (Pis. I to V), in this respect being unlike the thick, 

 strong cone scales of pines, which often have sharp, strong prickles. 

 Like the cone scales of the pines, however, they are firmly attached 

 to a central woody column, and never fall away until the cone is 

 rotted to pieces. Two seeds (PL I, b) are borne under each fertile 

 cone scale ; no seeds are produced by the usually much-aborted scales 

 at the two ends of the cones. The seeds are light and provided at 

 one end with a thin wing which renders them so buoyant that the 

 wind disseminates them widely. The seed-leaves, the first foliar 

 organs to appear after the seed germinates, are commonly from 5 to 

 about 15, or sometimes only 4 in number (PL III, b). 



The spruces are exceedingly important forest trees, and some are 

 much planted for ornament. They yield superior saw timber, the 

 straight and even grained wood being used for a great many commer- 

 cial purposes, including paper pulp, for which it is unsurpassed. 



Seven species are indigenous to North America, all of which occur 

 abundantly, or exclusively, within the United States. Four species 

 are distributed over the western half of the United States, and three 

 range mainly through northeastern United States and Canada, 

 while two of these extend, almost entirely in Canada, from the Great 

 Lake region into Alaska. ^ 



Species of this genus are of ancient origin, representatives of the 

 group having existed from the Middle Cretaceous period to the Re- 

 cent, while cones of both Picea canadensis and P. mariana, the white 

 spruce and black spruce of to-day, are abundant in postglacial 

 deposits at Chicago, 111. 1 



BLACK SPRUCE. 



Picea mariana (Mill.) B., S., and P. 



COMMON NAME AND EARLY HISTORY. 



This species has long been known as black spruce, a name probably 

 coined from the tree's most widely used technical name, Picea nigra, 



1 The writer is indebted for this statement of the geologic history of Picea to Dr. 

 Edward W. Berry, paleontologist, Johns Hopkins University, Baltimore, Md. 



