BALSAM FIR. ST?' 



winged seeds. Outside of each scale, at the bottom, is a bract ^ 

 resembling a transformed, winged fir leaf, the end of which, on a 

 mature cone, seldom protrudes enough to be noticed. These bracts 

 furnish a means of distinguishing balsam, Fraser, and Alpine fir. In 

 general, the relative lengths of the cone scale and this bract are means 

 to distinguish between the different native fu's, but in the case of 

 balsam the value of this distinction is lessened because of the occur- 

 rence of forms with slightly exserted or protruding bracts. 



The classification of Eraser fir as a distinct species rests not on the 

 protrusion of the bract, but on its spatulate and reflexed form. The 

 forms of balsam fir with slightly exserted 

 bracts need not, therefore, cause any confu- 

 sion, for though these do protrude a little, 

 they are not diiferent in shape from the 

 included form, and are neither spatulate nor 

 reflexed. (Fig. 5.) 



Since the bracts of Alpine fir never pro- 

 trude, this variant character in balsam is of 

 value in distinguishing it from Alpine fir. 

 Furthermore, the cone scale of Alpine fir is 

 larger than that of balsam, as shown in Fig. fig. s.-cone scale and bract, 



5 (h and C) natural size: a, Abies balsamea 



rm ■ T ' ' 1 1 (^•) Mlill.; b, Abies fraseri 



ims distmction, however, can not always (Pursh.) Lindi.; c, Abies lasio- 

 be relied upon, because the size and form of '^^^^ (Hoot.) Nutt. 

 the cone scales of Alpine fir vary. It is safer, therefore, to distinguish 

 Alpine from balsam fir by the form of the bract, which in the former 

 is conspicuously long pointed. 



REPRODUCTION. 



Under favorable conditions balsam fir bears fruit when about 20 

 years old and 15 feet high. Regular production of seeds, however, 

 does not begin before the age of 30 or 35 years. On high mountains, 

 above timber line, . scrubby balsam begins to bear seeds in large 

 quantities when from 23 to 25 years old. The amount of seeds borne 

 by individual trees depends, of course, on the size of the crown. As a 

 rule trees in a dense stand bear less seed than trees in the open. In a 

 mixed forest the dominant trees are prolific seeders, the intermediate 

 trees moderately so, while the suppressed trees produce no seed at all. 

 Although balsam fir produces some seed every year, plentiful seed 

 years occur only at intervals of two, three, and even four years. 



1 Discussion and Drawings of Cone Scales and Bracts, by William H. Lamb, Forest Service. 



