38 



A PRIMER OF FORESTRY. 



may not flud the right surroundings for successful ger- 

 mination, or the infant trees may perish for want of 

 water, light, or suitable soil. Where there is a thick 

 layer of dry leaves or needles on the ground, seedlings 

 often i^erish in great numbers because their delicate 

 rootlets can not reach the fertile soil beneath. The 

 same thing happens when there is no humus at all and 

 the surface is hard and drj^ The weight of the seed 

 also has a powerful influence on the character of repro- 

 duction. Trees with 

 heavy seeds, like 

 Oaks, Hickories, 

 and Chestnuts, can 

 sow them only in 

 their own neighbor- 

 hood, except when 

 they stand on steep 

 hillsides or on the 

 banks of streams, 

 or when birds and 

 squirrels carry the 

 nuts and acorns to 

 a distance. (See PI. 

 XYIII.) Trees with 

 light, winged seeds, like the Poplars, Birches, and 

 Pines, have a great advantage over the others, be- 

 cause they can drop their seeds a long way oft'. (See 

 figs. 31, 32.) The wind is the means by which this is 

 brought about, and the adaptation of the seeds them- 

 selves is often very curious and interesting. The wing 

 of a Pine seed, for example, is so placed that the seed 

 whirls when it falls, in such a way that it falls very 

 slowly. Thus the wind has time to carry it away before 

 it can reach the ground. In heavy winds Pine and other 



Fig. 36.— Mixed forest of Wbite Pine, Chestnut, 

 and Oak at Milford, Pa. 



