PLANT SOCIETIES 



321 



narrowness of the division permits plenty of light to 

 penetrate to the plant's lower leaves. It is also, doubt- 

 less, much easier for leaves like those of the yarrow, the 

 dog fennel, the tansy, the carrot, and their like, to with- 

 stand the action of 

 severe winds, to 

 which they are often 

 exposed, than it 

 would be for leaves 

 like those of the jack- 

 in-the-pulpit (see 

 Frontispiece), the 

 trilliums, the lily-of- 

 the- valley, and simi- 

 lar leaves. 



393. Transition of 

 a Plant from Shade 

 Conditions to Sun 

 Conditions. --It is 

 characteristic of 

 many kinds of forest 

 trees that the young 

 seedlings are much 

 more tolerant of 

 dense shade than the 

 adult trees are. 

 Sometimes their seeds will hardly germinate at all unless 

 thoroughly shaded, and the young trees for the first few 

 years flourish best in the shade. Afterwards most trees 

 need a good deal of sunlight, but they may live long 

 with a scanty supply of light. The red spruce sometimes 



i ii 



FIG. 227. I, a Shade-Plant (Clintonia) ; II, a Sun- 

 Plant, Dog Fennel (Maruta). 



