SEASONAL SUCCESSION IN A DECIDUOUS FOREST 233 



advantage of the short period when the forest is warm and sunny, 

 before tlie trees have leaved. They are active only about three 

 months and dormant during the remainder of the year. They are 

 northern plants and })erhaps are relicts of the glacial jieriod and 

 have developed the three-month habit during that period. 



The seedlings of many later blooming plants appear during the 

 prevernal season. 



Fig. 104. — Sanguinaria canadensis. A prevernal flower. 



C. Vernal Season.— The vernal season begins with the opening of 

 the forest tree leaves and lasts until near the middle of June. This 

 is the season of the later spring flowers, such as the Virginia cowslip 

 {Mertensia virginica), the May apple {Podophyllum peltatum), the 

 wild geranium {Geranium maculatum), the Solomon's seal {Poly- 

 gonatum bifiorvm), the wild spikenard {Smilicina racemosa), the 

 wild strawberry {Fragaria mrginiana) , and many others. The most 

 of these bloom during the month of May and by the first of June 

 there begins to be a scarcity of wild flowers. 



D. The Mstival Season.— The aestival season begins about the 

 middle of June and lasts until about the middle of August. At the 

 beginning of this season an entirely new crop of wild flowers appears, 

 but they are found in open places along forest margins, in meadows, 

 and along streams rather than in the shade of the forest. Many of 



