394 George E. Nichols, 



from those just described for Isle Royale. Here, as there, open- 

 ings due to windfall are a characteristic feature of the forest; 

 and the immediate sequel to windfall is a commonly prolific crop 

 of balsam. Some of the young trees may originate from seeds 

 shed previously to the windfall, but which have been lain dormant 

 on the ground for want of conditions suitable to germination. 

 Others doubtless arise from seeds shed only a short time before 

 the windfall, or else contemporaneously with or subsequent to it. 

 But many of the young trees represent specimens which were 

 already present in the forest previous to the windfall. For while 

 the reproduction of the balsam is most prolific in the windfall 

 areas, it is by no means confined to them. It is seldom that the 

 shade on the forest floor is sufficiently dense to prevent repro- 

 duction, and almost everywhere the undergrowth in a forest of 

 the climax type includes numerous small, scattered balsams, 

 mostly suppressed but ready to take advantage of any chance 

 opening which may occur in the canopy overhead. Such open- 

 ings, to be sure, are commonly due to windfall, since except in 

 protected situations the balsam seldom dies a natural death. It 

 is a not infrequent occurrence for groups of trees to be over- 

 thrown by the wind, thus giving rise to openings of considerable 

 extent, but more commonly it is only scattered individuals which 

 are blown down at one time. The influence of the openings thus 

 created is probably twofold: (/) more light is introduced into 

 the lower layers of vegetation, and {2) wherever sunlight reaches 

 the forest floor the moss carpet, together with the more or less 

 spongy underlying layers of duff and humus, tend to become 

 somewhat dried out and in consequence warmer and better 

 aerated. This latter indirect influence, the possible significance 

 of which is suggested by Cooper ('13, p. 20), it seems to the 

 writer, is of fully as great importance here in northern Cape 

 Breton, at least so far as the balsam is concerned, as is the direct 

 influence of increased illumination. The understory of balsams 

 in a deciduous forest is much more thrifty than that in a conif- 

 erous forest, a circumstance which might be explained by the 

 more favorable soil conditions there : so far as shade is con- 

 cerned, this is generally greater in a deciduous than in a 

 coniferous forest, at least during the growing season. But with- 

 out question increased illumination is a very important direct 

 factor, and perhaps the most important one, affecting the growth 



