MESOPHYTE ASSOCIATIONS. 24:7 



Not only is protection during the cold period secured 

 by deciduous forests through the falling of leaves, but the 

 development of scaly buds is an adaptation to the same 

 end. By means of these overlapping, often hairy, and even 

 varnished structures, delicate growing tips are protected 

 during the cold season. The development of cork, also, on 

 the older parts, is a measure of protection. 



Although the trees are the dominant plants of a forest as- 

 sociation, it must not be forgotten that numerous other forms 

 are associated with them. At a lower level stand the shrubs, 

 below these the tall herbs, then the low herbs and grasses, 

 and finally close to the soil mosses and lichens occur. 

 These different strata, as they are called, represent differ- 

 ent habits in reference to light, the lower strata being made 

 up of shade plants as compared with the upper strata. In 

 fact, the shade habit has become so established in many 

 plants of the lower strata that they depend upon the pres- 

 ence of the overshadowing strata, and could not live with- 

 out them. 



The vernal habit is also an interesting feature of decidu- 

 ous forests. It is a matter of common observation that the 

 rich display of " spring flowers " occurs in forests and wooded 

 glens before the trees come into full foliage. The working 

 season of these vernal plants is before the dense foliage of 

 the forest shuts off the light. Accordingly, they are mostly 

 geophilous in habit (see §146), sending up their shoots or 

 leaves with great rapidity from underground tubers, root- 

 stocks, etc., and completing their vegetative work in the 

 short period during which the light is available. After the 

 forest leaves are fully developed the spring flowers disap- 

 pear, waiting in their subterranean retreats for the next 

 short period of activity. Two prominent forms of the ver- 

 nal habit may be observed. The leaves may appear before 

 the flowers, as in Erythronium and HydrophyUum ; or they 

 may appear after the flowers, as in Hepatica and Sanguinaria. 

 One of the wild leeks (Allium tricoccum) has developed a 



