COLD TEMPERATE FOREST FORMATIONS 557 



character of the forest, just as it does in tropical districts with wet and 

 dry seasons ; the forest is typically tropophilous. On account of the 

 predominating oecological importance of the summer-heat the tropophilous 

 forest of the cold temperate belt may be termed summer-forest or summer- 

 green forest. 



Forests of the belts with cold winters are more generally differentiated 

 into broad-leaved forest and coniferous forest than are those of warmer 

 zones ; yet, especially in North America, there is no want of mixed forests, 

 and the present sharp separation of the two is frequently, especially in 

 Europe, due to the intentional interference of man. On the whole, coni- 

 ferous forests occupy the colder districts, and broad-leaved forests the 

 more temperate ones ; the latter therefore occur chiefly in the south and 

 within range of the maritime climate ; the former in the north, as well 

 as in regions of greater altitude. To this rule there are however many 

 exceptions, which are determined partly by the nature of the soil and 

 partly by the peculiarities of particular species. For instance, in the broad- 

 leaved districts pine-forest occurs on sandy and peaty soils, while birch- 

 wood can go beyond the coniferous forest both in latitude and in altitude. 



ii. THE BROAD-LEAVED SUMMER-FOREST. 



Even at the height of the vegetative season the appearance of the broad- 

 leaved summer-forest is very different from that of the evergreen forest, and 

 in particular of the rain-forest. When regarded from above, it extends like 

 an almost uniformly bright green expanse, in striking contrast with the richly 

 shaded but chiefly dark canopy of the tropical forest. The profile is lower, 

 more even and more regular, because the trees of the canopy are less varied 

 in their height and mode of branching. 



Whilst the interior of the rain-forest is usually full to repletion, that 

 of the broad-leaved summer-forest frequently presents a picture of vacuity. 

 The underwood is often entirely absent when the trees are crowded, and 

 exhibits some degree of luxuriance only in thinly stocked woods or at 

 the edge of the forest ; but it always permits an unimpeded view into the 

 interior of the forest. Here, instead of the five tiers of the tropical rain- 

 forest, only three at the most occur, between the tree-trunks some shrubs 

 appearing, and between the latter some terrestrial herbs and mosses. 

 This forest in its most luxuriant and lofty form consists, however, 

 essentially of trees alone. Underwood is absent or thinly distributed, and 

 the ground, covered as it is with the decomposing debris of the fallen 

 leaves, supports, at least during summer, only scant)' herbs, ferns, and 

 mosses, which on the approach of autumn are reinforced by a crowd 

 of pileate fungi. But spring is characterized by a richer though transient 

 flora of flowering plants. 



Lianes, those unfailing constituents of the rain-forest, are, except in 



