89 SUCCESSION 



earth's covering of .vegetation. The first settlers on the 

 bare ground are crustaceous lichens, minute mosses and 

 algae. On the substratum prepared by them larger lichens, 

 mosses and algae are able to gain a footing. The dead fila- 

 ments, stems and leaves pertaining to this second gener- 

 ation arrest dust in the air and mud in the water, and thus 

 prepare a soft bed for the germs of a third generation, which 

 on rocks consists of grasses, composites, pinks and other 

 small herbs, and in water of pond weeds, water-crowfoots, 

 hornwort and various plants of the kind. The second gener- 

 ation is produced in greater abundance than the first, and 

 the third developes more luxuriantly than the second. The 

 third may be followed by a fourth, fifth and sixth. At all 

 times and in all places, we see younger generations displac- 

 ing the older and building upon the foundations laid by their 

 predecessors. The first settlers have a hard fight with un- 

 compromising elements to seize possession of the lifeless 

 ground. Years go by before a second generation is enabled 

 to develop in greater luxuriance upon the earth prepared by 

 the first occupiers; but there is no cessation in the produc- 

 tive and regulative effects of vegetable life, and its energy 

 and aptitude in the work result in the erection of its green 

 edifices over wider and wider areas. New germs are estab- 

 lished upon the smouldered dust of dead races, and others 

 on the plant forms adapted to the altered substratum, and 

 so, for hundreds and thousands of years, the changes go on, 

 until at length the tops of forest trees wave above a black 

 and deep soil, the battlefield of a number of bygone gener- 

 ations. At lease three successive series of settlers may thus 

 be traced upon every spot, and not infrequently the number 

 is four or five. Now, if each of these groups corresponds to 

 a particular community, which is as a matter of fact the 

 case, the phenomenon described must produce the same im- 

 pression as though the communities became transformed in- 

 to one another in the course of time. It is therefore neces- 

 sary to recognize the existence of the incipient and decadent 

 stages as well as that of predominance. In the incipient 

 stage, relics of the community which previously occupied 



