262 



SUCCESSION IN EURASIA. 



Scott-Elliott (1907) has found the following stages in the succession on 

 exposed trap rocks in Scotland: 



(1) Lichen stage, Lecidea, Lecanora, Parmelia, Cladonia, etc. ; (2) moss stage, 

 species of Rhacomitrium, with other mosses and lichens, which form a distinct 

 soil; (3) Vacdnium stage, Vacdnium myrtillus, Calluna, and heath grasses; 

 in wet situations Sphagnum accmnulates and leads to the development of 

 moor and heath, whUe in dry places this leads to (4) herbaceous stage, Scabiosa, 

 Thymus, Campanula rotundifolia, Teucrium, Viola, etc.; (5) Z7Zea; stage, Ulex, 

 and Cytisus scoparius; (6) rosaceous stage, Rosa, Crataegus, and Pints; (7) oak 

 stage. 



Yapp (1908) has arranged the population of Wicken Fen into 6 groups and 

 14 subgroups on the basis of decreasing water-content. These correspond 

 essentially to stages and substages of the hydrosere: 



C. Wet-marsh plants — Continued. 



9. Carex spp., Orchis, Caltha, Menyan- 

 thes. 



D. Intermediate forms. 



10. Lastrea, Iris, Thalictrum, Lythrum, 



Mentha, etc. 



11. Calamagrostis, Agroatis, PotentiUa, 



Valeriana, etc. 



E. Dry-marsh plants. 



12. Molinia, Aira, Peucedanum. 



13. Spiraea vlmaria, Symphytum, Eupor 



torium. 



A. Aquatics. 



1. Chara, NiteUa, etc. 



2. MyriophyUum, Potamogeton, HoUonia, 



etc. 



3. Nymphaea, Sparganium natans, etc. 



B. Semi-aquatics. 



4. Sagittaria. 



5. Sdrpus lacustris. 



6. Bviomus, Sparganium erectum, Alis- 



mu. 



C. Wet-marsh plants. 



7. Phragmites. 



8. Juncus ohtusifiorus, Cladium. 



Species of Rhamnus and Salix invade the drier areas, forming thickets, and 

 are succeeded by Sorhus, and Quercus, which foreshadow the final forest. 



Margerison (1909) has described the development of vegetation in disused 

 quarries in Yorkshire, distinguishing four stages, viz, pioneer, first, second, and 

 third transitional or intermediate: 



From the wide range of conditions afforded by quarries, the pioneer stages 

 are greatly mixed and confused, though the usual sequence of algae, lichens, 

 mosses, herbs, and grasses is more or less evident. In one small area of a few 

 square feet, practically all the life-forms were represented, namely, algae, 

 mosses, herbs {Senecio), grasses {Aira), scrub {Calluna), and trees {BelvSa). 

 The first intermediate stage is marked by Betula, Lonicera, Sambucus, Rvbus, 

 Calluna, Senecio, Aira, Poa, and ferns. In the second stage, Pteris has become 

 the dominant of the undergrowth, and mountain-ash, oak, and sycamore have 

 invaded the deeper soils. The third stage consists of birch and sycamore, with 

 some oak and mountain-ash. Corydalis, Arum, Mercurialis, and SdUa have 

 entered from the surroimding woods, and the original forest is being rapidly 

 approximated. 



Elgee (1910) has studied the revegetation of biu-ned moorlands, or "swid- 

 dens," in Yorkshire and has noted the sequence of plants which appear after 

 burning until Calluna again becomes dominant : 



The first vegetation may consist of lichens, Cladonia, and mosses, Poly- 

 trichum, etc., or of annual plants, Aira praecox. The succeeding stages show 

 a temporary dominance of subdominant species of the final association. On 



