HISTORICAL 97 



Douglas (t889) used the term succession in combating the 

 then prevalent idea, that, when a forest is once destroyed, a 

 similar forest could never again be established on the same 

 spot. He pointed out that the period necessary fur such re- 

 establishment would depend largely upon the mobility of 

 the trees concerned, but that it was finally to be determined 

 by the persistence of the species. 'Warmmg (t890) found in 

 the marshy regions along the east coast of the North Sea 

 that Zostera filtered out and retained the fine particles of soil 

 in the deeper water, resulting in the formation of mud 

 banks, while algae and Salicornia herbacea filled the same 

 ofBce in shallow water. As the ground became higher and 

 dryer, Glyceria replaced Salicornia, and was accompanied by 

 Triglochin, Suaeda, Plantago, Glaux, Atriplex, etc. ; this vege- 

 tation was then in its turn driven out by Juncus, Sordeum, 

 Festuca, Lepturus, Armeria, Artemisia, etc. Kihlmann (1890) 

 studied the gradual drying up and disappearance of the 

 Sphagnum swamps, a phenomenon of frequent occurrence in 

 Russian Lapland. Sphagnum is slowly replaced by the more 

 xerophytic mosses and by lichens. The earlier fruticulose 

 forms are followed by a crust of Lecanora tartarica, in which 

 grow feebly Empetrum, Ledum, and Vaccinium myrtillus. The 

 succession is then closed, exceot where the lichen crust is 

 destroyed by some accidental agency. Kihlmann further 

 found that young dense growths of birch, in which no con- 

 iferous seedlings appeared, arose where the forests of red 

 fir had been burned off, and he concluded that this was due 

 to the difference in the time necessary for the ripening of 

 their seeds. The fact that the formation was still young 

 and dense would seem simply to indicate that the fir had 

 not yet found the proper conditions for invasion, conditions 

 which sooner or later must occur. 



Kerner (1890 : 267,895), without paying attention to par- 

 ticular formations, summed up in a graphic though some- 

 what general way certain main facts of succession. 

 "This mechanical retention and storage of dust by 

 rock-plants and of mud by aquatic plants is of the 

 greatest importance in determining the development of the 



