114 



Canadian Forestry Journal, March, 19/9 



THE MAKING OF A SPRUCE TREE 



By Dr. C. D. HoiD^e, Faculty of Forestry, University of Toronto. 



ARTICLE No. 2. 



From the time the yellow powder described 

 in the former article dusts the female flower 

 to the actual beginning of the new tree a month 

 or more may elapse and after that it is at least 

 another month before the growing substance 

 actually resembles a tree in form. At this time 

 very tiny leaves appear and there are structures 

 that later develop into stem and root. The 

 little tree is completely enclosed in a very deli- 

 cate membrane on the outside of which ac- 

 cumulates a white pulpy mass of food material 

 for the young plant to live upon, during the 

 germination period, until it can establish itself 

 in fhe soil. The moist food substance is in its 

 turn entirely surrounded by a heavy thick 

 membrane impregnated with oily or waxy water- 

 proof material, so that neither the stored food 

 or the little treelet is in danger of drying out. 



The structure we have been describing may 

 now be called a seed. It consists of three prin- 

 cipal parts: (1) an outside protective coat, 

 varying from light brown to nearly black in 

 color according to the kind of spruce tree; (2) 

 stored food material occupying most of the 

 space, and (3) embedded in the middle of the 

 latter a miniature tree which has already de- 

 veloped root, stem and leaves, although it is 

 not much more than one-sixteenth of an inch 

 long. 



Cone Development. 



In the meantime the structures on which the 

 seeds are borne have undergone growth 

 changes: the scales have enlarged and become 

 woody. In August the cones are the size of the 

 little finger to the first joint and they are no 

 longer erect, but bend over and hang down- 

 ward. From the middle of September to the 

 middle of October, according to the kind of 

 spruce and its location, the cones reach their 

 final size, usually between one and two inches 

 long; the seeds undergo the finishing touches 

 of the ripening process; their coats dry and 

 glaze; the little channels through which they 

 received nourishing fluids from the mother-tree 

 are cut off. Future spruce trees are about to 

 be separated from all parental trees and to be 

 thrown out into what may prove for most of 

 them a very cold and hostile world. However, 



before we follow a little spruce imbedded in 

 the seed farther in its career, let us turn aside 

 to some general considerations of seed pro- 

 duction. 



When Trees Bear Seed. 



The age at which a spruce tree begins to 

 bear seed varies with the conditions in which it 

 grows. In open pastures and old fields fully 

 exposed to light and in good soil a tree may 

 produce seed when only fifteen or twenty years 

 old; in plantations and pure stands of second 

 growth, cones may appear when the trees are 

 thirty years old, but full production begins at 

 about forty years of age. Under ordinary for- 

 est conditions a tree does not bear seed until 

 it frees itself from the shade of its neighbors 

 and receives full light exposure in its higher 

 branches, that is, until it gets into the upper 

 forest crown cover. This happens in a virgin 

 forest where the spruce is associated with hard- 

 woods, usually not before the tree is five or six 

 inches in diameter. According to growth 

 studies made in Quebec in a mixed forest (hard- 

 woods and softwoods) a red spruce tree at that 

 diameter would be close to one hundred years 

 old. 



When a tree breaks through the forest crown 

 cover and gets up into the light, under the 

 stimulus of additional exposure to the sun, it 

 develops an increased number of branches, 

 especially the small side branches on the main 

 limbs. As foresters express it: "The crown 

 thickens". When the crown is thickest, there 

 is the largest number of small branches. The 

 cones are borne on these small branches and, 

 therefore, this is the time of greatest seed pro- 

 duction. This comes in the mixed forest when 

 the spruce tree is about one foot to one and a 

 half feet in diameter, or in other words, when 

 the tree is between 150 and 200 years old. From 

 this time on the vigor of the tree usually declines 

 and with it seed production, but it is maintained 

 to an advanced age. In the summer of 1917 I 

 cut a red spruce over 300 years old and it had 

 a peck of plump cones on its branches. If we 

 assume, as above, that this tree began bearing 

 at 100 years of age, then it has had over 200 



