PLANT ECOLOGY. 143 



another there according to some accident of environment. On 

 the firm ground, but within root-reach of the water, grow the 

 bonesets and vervains. From the foot of the hill right up to 

 its crest, on slope and terrace, community after community 

 may be distinguished. 



In one such delightful situation that the writer often visits 

 the wooded slope presents a zonal series of trees, another of 

 shrubs, and a third of herbs. Tamarac and willow reflected 

 in the water are backed by basswood and soft maple, and 

 these in turn are surmounted by oak, hickory and hawthorn. 

 The shrubbery begins with heaths and poison sumac, high 

 cranberry and dogwoods; it ceases in the close shade but 

 re-appears at the summit in gooseberry and witch-hazel. The 

 low plants, beginning with the half-afloat sphagnum, in whose 

 bosom nestle cranberry and sundews, pitcher-plants and 

 orchids, lead on to a splendid company of shade-loving ferns 

 and water parsnip, turtle-heads and labiates up to golden-rods 

 and asters. 



What qualities in these plants and what elements in the 

 environment combine to bring these different species so 

 frequently together 1 These questions challenge our attention 

 with ever increasing interest. 



Relations to Moisture. — In such a situation as the one just 

 referred to one may see plants in a great variety of relations 

 to moisture, light, air and food. Another view is obtained 

 by studying them in extended areas of particular kinds. 

 Those that favor dry sandy tracts possess the means of 

 retaining the water they absorb from the scanty supply. 

 Some of them curl their leaves backwards to close their 

 transpiring pores ; some have thick succulent stems or leaves 

 that store water against the drying days ; others have their 

 pores deep sunk and protected by scales and hairs that control 



