In Britain and in most of its Continental habitats two varieties exist, regarded by many as distinct species: one, Q.
In fresh-water Hydromedusae the life-cycle is usually secondarily simplified, but in marine forms the life-cycle may be extremely complicated, and a given species often passes in the course of its history through widely different forms adapted to different habitats and modes of life.
The cotton-wood timber, though soft and perishable, is of value in its prairie habitats, where it is frequently the only available wood either for carpentry or fuel; it has been planted to a considerable extent in some parts of Europe, but in England a form of this species known as P. monilifera is generally preferred from its larger and more rapid growth.
In these northern habitats it attains a large size; the wood is very soft; the buds yield a gum-like balsam, from which the common name is derived; considered valuable as an.
Thus A plant formaiion is a group of associations occupying habitats - iich are in essentials identical with each other.
Physically and physiologically wet habitats, with the accompanying plant communities of lakes, reed swamps, and marshes.
Physically and physiologically dry habitats, with the accompanying plant communities of sand dunes and sandy heaths with little humus in the soil.
Habitats of medium wetness, with the accompanying plant communities of woodlands and grasslands.
Habitats poor in.
Habitats rich in mineral salts, especially calcium carbonate, poor in acidic humous compounds, and characterized by ash woods, beech woods, and calcareous pasture.
Although many plants typical of fresh water are able to grow also in brackish water, there are only a few species which appear to be quite confined to the latter habitats in this country.
Xerophytes.These plants have devices (a) for procuring water, (b) or for storing water, (c) or for limiting transpiration; and these adaptations are obviously related to the physically or physiologically dry habitats in which the plants live.
With regard to the occurrence of plants, such as Juncus effusus, which possess xerophytic characters and yet live in situations which are not ordinarily of marked physiological dryness, it should be remembered that such habitats are liable to occasional physical drought; and a plant must eventually succumb if it is not adapted to the extreme conditions of its habitat.
In its native habitats it is said to endure for several centuries; but in those countries from which the commercial supply of its timber is chiefly drawn, it attains perfection in from 70 to 90 years, according to soil and situation.
If we are to accept and profit by Dorpfeld's nomenclature, we must be satisfied that, in their later historic habitats, both Lycians and Carians showed unmistakable signs of having formerly possessed the civilizations attributed to them in prehistoric times - signs which research has hitherto wholly failed to find.
Foxes are still found in considerable numbers in suitable habitats; opossums, skunks and raccoons are plentiful in some parts of the state; and rabbits and squirrels are still numerous.
(h) It has been shown above how the animistic creed postulates the existence of all kinds of local spirits, which are sometimes tied to their habitats, sometimes free to wander.
This is the more remarkable seeing that the habitats of the two are separated by such an enormous tract of country.
The habitats which they affect are the hot, dry regions of tropical America, the aridity of which they are enabled to withstand in consequence of the thickness of their skin and the paucity of evaporating pores or stomata with which they are furnished, - these conditions not permitting the moisture they contain to be carried off too rapidly; the thick fleshy stems and branches contain a store of water.
Starting with the stem forms the descendants of which have passed through either persistent or changed habitats, we reach the underlying idea of the branching law of Lamarck or the law of divergence of Darwin, and find it perhaps most clearly expressed in the words "adaptive radiation" (Osborn), which convey the idea of radii in many directions.
It is to distinguish them from the grey, or timber, wolves that coyotes have received the name of "prairie-wolves"; the two titles indicating the nature of the respective habitats of the two species.
It grows as rapidly and attains as large a size in British habitats suited to it as in its home on the Alps, and often produces equally good timber.
Habitats and Distribution of Lichens.
Sometimes various lichens occur abnormally in such unexpected habitats as dried dung of sheep, bleached bones of reindeer and whales, old leather, iron and glass, in districts where the species are abundant.
As a rule lichens grow commonly in open exposed habitats, though some are found only or chiefly in shady situations; while, as already observed, scarcely any occur where the atmosphere is impregnated with smoke.
It is an abundant tree in the northern parts of Britain, even as far as Sutherland, and is occasionally found in the coppices of the southern counties, but in these latter habitats seldom reaches any large size; throughout northern Europe it abounds in the forests, - in Lapland flourishing even in 70 0 N.
ACCLIMATIZATION, the process of adaptation by which animals and plants are gradually rendered capable of surviving and flourishing in countries remote from their original habitats, or under meteorological conditions different from those which they have usually to endure, and at first injurious to them.
In Germany, both on the mountains and the sandy plains, woods of " kiefer" are frequent and widely spread, while vast forests in Russia and Poland are chiefly compqsed of this species; in many northern habitats it is associated with the spruce and birch.
Flourishes, and the timber is always indifferent; it is usually said that the wood is best in the cold climate of its more northern habitats, but a trunk (4 ft.
Southern Austria and the adjacent countries are the natural habitats of this pine; it seems to flourish best on rocky mountain sides, but in England grows well on sandy soils.
It is represented to-day by the still undeserted habitats of Zuni (in New Mexico) and Tusayan; the Moquis, after the Zunis, are in customs and traditions the best survival of the ancient civilization.
As Coulter and Chamberlain express it, " the habitats of the Gymnosperms to-day indicate that they either are not at home in the more genial conditions affected by Angiosperms, or have not been able to maintain themselves in competition with this group of plants."
But the habitats overlap, and persimmons and magnolias of different species are common and notable in both areas.
In the case of the southern continents the difficulty is, however, to determine whether allied groups of mammals (and other animals) have reached their present isolated habitats by dispersal from the north along widely sundered longitudinal lines, or whether such a distribution implies the former existence of equatorial land-connexions.