if such correspondence is lacking, either the climate has changed 

 or the plant has very likely been transferred from its original 

 home. For example, in Czechoslovakia the autumn crocus, Col- 

 chicum autumnale, a native of the Mediterranean Region, flowers 

 in the autumn and ripens fruit in the spring, contrary to the be- 

 havior of its associates which bloom and fruit in the same year. 

 The great diversity in periodicity among species in the present 

 flora of Europe can be explained by the great climatic changes 

 that have occurred there, accompanied by migrations of species. 

 The oaks, Quercus robur and Q. sessiliflora, and the beech, Fagus 

 sylvatica, apparently were adapted in the past to a warmer climate 

 and have not yet, even after thousands of years, become adapted 

 to the climatic rhythm of their present environment. This lack of 

 complete adaptation is revealed in the abscission layer remain- 

 ing alive and green during the entire winter, and in the falling 

 of their leaves, which coincides with the development of new leaf- 

 buds, similar to the habit of the evergreen broad-leaved 

 species. Plants which do not pass through a full cycle of develop- 

 ment, or a normal development, indicate that they originated in 

 some other kind of community than the one of which they now 

 form a part, as exemplified by the failure to flower of Caltha 

 palustris in a dry meadow, or the failure of Vaccinium uliginosum to 

 flower and fruit in Novaya Zemlya. 



Most communities have a definite aspect at diflferent seasons 

 of the year. The chief aspects are the prevernal, or early spring; 

 the vernal, or spring; the aestival, or summer; the serotinal, or 

 autumn; and the hiemal or hibernal, winter. It is interesting to 

 keep records of phenological events such as the dates of appear- 

 ance of certain kinds of seedlings in various years, the inception 

 of growth of perennials, the opening of leaf and flower buds on 

 certain trees, the full expansion of the leaves, and the appear- 

 ance of first flowers, first ripe fruits, last flowers, and the comple- 

 tion of the dissemination of the fruits or seeds. Each species and 

 each stage has its own specific rate of development and growth. 

 These physiological phenomena have practical value in integrat- 

 ing many environmental factors, and can then be used to pre- 

 dict the time of harvest, when a range is ready for grazing, and 

 other practices. 



Axmalytic CHaracteiristics of the Cosnmimnity • 87 



