4 BULLETIN 32*7, U. S. DEPARTMENT OP AGRICULTURE. 



doubtless suggested by the dark blue-green foliage, which contrasts 

 strongly with the ashy or glaucous green hue of the white spruce 

 found in the same general region. " Swamp spruce," " bog spruce," 

 and " muskeg spruce," are local names applied to it when found grow- 

 ing in wet, marshy places. Black spruce was doubtless well known 

 to the French and English settlers in eastern Canada and New Eng- 

 land 'at least as early as the seventeenth century, but the first defi- 

 nite account of it was not published until 1755, 1 and then not under 

 a technical name. The black spruce was first technically described 

 and named "Abies mariana Miller" in 1768. From 1800 to 1888 it 

 was, however, known to botanists and horticulturists as Abies nigra 

 and as Picea nigra, its present accepted name, Picea mariana (based 

 on A. mariana) , not being established until 1888. 



Several different forms of the black spruce have been named as 

 distinct species (now doubtfully tenable), while about seven named 

 horticultural varieties are distinguished in cultivation. 2 



DISTINGUISHING CHARACTERISTICS. 



Black spruce is mainly an eastern and far northern species, in- 

 cluded here because it occurs in the Canadian Rocky Mountain region. 

 There it is from 25 to 40 feet high and from 4 to 8 inches in diameter. 

 In its wider eastern range this tree exceptionally attains a height of 

 from 50 to 75 feet and a diameter of about 1 foot ; very occasionally 

 "it grows to 100 feet in height and 2 to 3 feet in diameter. The crown 

 is characteristically open and irregular, extending to the ground, 

 except in middle-aged or old trees grown in a dense stand, where the 

 lower half of the trunk is clear of branches. The usually short, slim 

 branches, often distant from each other, commonly droop at their 

 ends, but some forms of the tree have peculiarly stiff branches. A 

 stunted form of this tree growing in wet marshes has tufts of very 

 short branches, only or chiefly, at the top of the stem. The great 

 variation in the habit of the branches and density of the crown 

 appears to be due entirely to differences in habitat, which ranges 

 from wet, boggy marshes to dry uplands. 



The foliage is a deep blue-green, with a tinge of whitish, the 

 short leaves (PI. I) standing out on all sides of the branches. A 

 cross section of the leaves shows two minute resin ducts close to the 

 surface and near the angles of the leaf. The bark of old trees is 

 thin and composed of small ashy-brown scales. The young twigs of 

 a season's growth are usually a pale russet-brown, coated with small 

 hairs of similar color. 



1 Du Hamel, Traite des arbres et arbustes,, I, 17, 1755. 



2 See Nomenclature of Arborescent Flora cf U. S. (Bull. 14, Div. Forestry, U. S. Dept. 

 Agr.), 34, 1897. These "varieties" are distinguished chiefly by slight differences in the 

 shape of the crowns and by the color of the foliage. The variety known in cultivation as 

 " Picea nigra Doumetii " is very distinct in its narrowly pyramidal, dense crown. 



