CHAP, xci MESOPHYTIC BUSHLAND 329 



an intermediate type one may safely regard bushland described by 

 Giinther Beck l as composed of Primus spinosa, Crataegus, Rosa, Cornus, 

 Berberis, blackberry, raspberry, and other plants, which deck themselves 

 with a snow-white show of blossom in spring and bear glossy berries or 

 drupes in autumn. Countless perennial herbs clothe the ground, and the 

 plants that demand light in high-forest congregate in such bushland. In 

 many places these species that give rise to bushland produce underwood 

 beneath such light-demanding trees as Fraxinus, Populus tremula, and 

 Prunus Padus. 



Allied to the preceding are certain bushlands or thinly wooded forests 

 described by Blytt as occurring on rubble-heaps in the south of Norway. 

 These are composed of Corylus, Ulmus, Tilia, Fraxinus, Acer, Sorbus, 

 Quercus, Rosa, Crataegus, and others, under the shelter of which develops 

 a rich flora of more southern forms, including aromatic Labiatae, Gera- 

 nium, Hypericum, Dentaria bulbifera, Lathyrus sylvestris, L. vernus, 

 L. niger, and various grasses. By the term ' rubble-heap ' 2 is meant a soil 

 composed of loose stones that have been cast down to form an accumula- 

 tion (talus). When such a heap abounds in species and vigorous indi- 

 viduals, this is due to several causes : First, wind causes an accumulation 

 of inorganic and organic particles among the stones. Secondly, water 

 accumulates beneath the stones and can evaporate only with difficulty. 

 Thirdly, this stony soil readily becomes heated. Fourthly, such rubble- 

 heaps nearly always occur on sloping spots at the foot of walls of rock, 

 where they are easily heated, if the aspect of the slope be not too 

 unfavourable. 



Mesophytic bushlands owe their existence to divers causes. Those 

 mentioned as occurring in Polar lands and high up mountains occur in 

 spots where the conditions for growth (temperature) are unfavourable to 

 forest, but are too favoured for mere mat- vegetation. Other bushlands 

 are the result of cultivation, since they represent the remnants of forests 

 which have been felled by human agency and are still kept under by 

 hostile circumstances that result directly or indirectly from human 

 interference : belonging to this type are oak-bushland in Jutland, 3 bush- 

 land in the Balkan peninsula composed of oaks, Rhus Cotinus and others, 4 

 also the hornbeam-scrub mentioned by Focke 5 as occurring above the 

 level of marsh on German coasts bounding the North Sea. * Bush-pasture ' 

 in the Alps is likewise a ' zoogenetic ' admixture of more than one type of 

 vegetation, according to Brockmann-Jerosch. 6 



CHAPTER XCII. DECIDUOUS DICOTYLOUS FOREST 



DECIDUOUS dicotylous forest is that type of forest in which the trees 

 are leafless for a longer or shorter season of the year, and are foliaged 

 during some (five to eight) months. 7 This behaviour is closely correlated 



G. Beck, 1890-3. a See p. 246. 



Vaupell, 1863; Warming, 1907. 



Grisebach, 1872; Adamovicz, 1898; Vahl, 1907. 6 Focke, 1893, P 261. 



Brockmann-Jerosch, 1907. 



The ash-tree in Denmark may bear foliage for only four months. The beech- 

 tree in Madeira apparently is in leaf for eight months. 



