HISTOBICAL 95 



In 1887, Hult investigated the invasion and substitution of 

 one formation by another in the alpine regions of Lapp- 

 mark. He found that in the dryer places Gladineta and 

 Alectorieta finally replaced all other associations, while in 

 moist places grass and herbaceous formations passed into 

 formations of dwarf shrubs, the universal rule being a 

 transition from hygrophilous to more or less xerophilous 

 conditions. 



Treub (J888), after the destructive eruption of Krakatau in 

 1883, found that Cyanophyceae were the first plants to appear 

 on the new soil : these were followed by an exclusive vege- 

 tation of ferns, in which a few phanerogams, especially 

 composites, began to appear by the third year. Senft (J888) 

 traced the development of vegetation on naked xerophytic 

 slopes of the Horselbergen. The pioneers were lichens, 

 especially Parmelia, followed soon by mosses, Hypnum, Bar- 

 Mla, and after a few years by Festuca ovina, which appeared 

 first in the rock clefts and then spread into a thick sod. 

 The next invaders were all grasses, Koeleria cristata, Briza, 

 Melica, and Br achy podium, which almost entirely replaced 

 Festuca in three years: the grasses were then invaded, 

 though not completely replaced, by herbs, Helianthemum, 

 VerbascuTYi, Lactuca scariola, Agrimonia eupatoria, Anemone, 

 Oentiana, etc., and by a few shrubs, Juniperus communis, 

 Viburnum lantana, and Crataegus. Later appeared Ligustrum, 

 Cornus and Bhamnus, and still later, Cotoneaster, Crataegus, 

 Frunus and Bosa, forming a thicket twelve years after the 

 inception of the succession. The last stage was a forest of 

 Sorbus, Corylus. Fagus, Alnus, Tilia and Acer. Krassnoff 

 (J883, 1886) found that forest clearings in the Altai were 

 recovered partly by persistent forest plants, and partly by 

 invading steppe plants, Paeonia, Bupleurum,Aconitum,Chamae- 

 nerium, Delphinium, Geranium, Thalictrum, etc. In certain 

 places where fire had destroyed the forest growth, the 

 ground was still covered after a lapse of many years with a 

 tall herbaceous growth of Eelleborus, Aconitum, Thalictrum, 

 Paeonia, Pedicularis and Bosa. li seems highly improbable. 



