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SCIENCE. 



[Vol. XL No. 275 



the natural environment to his wants, and thus creates an envi- 

 ronment for himself. Thus it is that we do not discover an 

 aquatic variety of man ; yet he dwells upon the sea, and derives 

 sustentation from the animals thereof by means of his arts. An 

 arboreal variety of man is not discovered, but the forests are used 

 in his arts, and the fruits of the forests for his sustentation. An 

 aerial variety of man is not discovered, but he uses the winds to 

 propel his machinery and to drive his sails ; and, indeed, he can 

 ride upon the air with wings of his own invention. A boreal variety 

 of man is not discovered, but he can dwell among the everlasting 

 snows by providing architectural shelter, artificial warmth, and 

 bodily protection. 



Under the influences of the desert, a few plants secure a con- 

 stitution by which the moisture imbibed during brief and inter- 

 mittent rains is not evaporated : they become incrusted with a 

 non-porous glaze, or contract themselves into the smallest space, 

 and exist without life, until the rain comes again. Man lives in 

 the desert by guiding a river thereon and fertilizing the sands with 

 its waters, and the desert is covered with fields and gardens and 

 homes. Everywhere he rises superior to physical nature. The 

 angry sea may not lash him with its waves ; for on the billows he 

 builds a palace, and journeys from land to land. When the storm 

 rises, it is signalled from afar, and he gathers his loved ones under 

 the shelter of his home, and they listen to the melody of the rain 

 on the roof. When the winds of winter blow, he kindles fossil sun- 

 shine on his hearth and sings the song of the Ingleside. When 

 night covers the earth with darkness, he illumines his path with 

 lightning light. For disease he discovers antidote ; for pain, 

 nepenthe ; and he gains health and long life by sanitation ; and 

 ever is he utihzing the materials of nature, and ever controlling its 

 powers. By his arts, institutions, languages, and philosophies he 

 has organized a new kingdom of matter over which he rules. The 

 beasts of the field, the birds of the air, the denizens of the waters, 

 the winds, the waves, the rivers, the seas, the mountains, the val- 

 leys, are his subjects. The powers of nature are his servants, and 

 the granite earth his throne. 



INFLUENCE OF FORESTS UPON THE CLIMATE OF 

 AUSTRALIA. 



In connection with the discussion that is going on at the present 

 time in reference to the influence of foresis upon rainfall in the 

 western parts of the United States, the following remarks of Dr. 

 R. von Lendenfeld on the influence of deforestation upon the climate 

 of Australia, which were published in the February number of Pcter- 

 tnanns Mittcilungen, will be of interest. The influence of the 

 forest upon the climate in the damp regions of the temperate zone, 

 for instance in central Europe, is undoubtedly such as to increase 

 the humidity of a place. The roots of the trees, forming a 

 network, retain the earth on steep slopes, and thus prevent the 

 water from running off rapidly. On slopes without forest or vege- 

 tation the water rushes downward : it is collected in streamlets and 

 rivers, and carried into the ocean before much, if any, evaporation 

 has taken place. 



Evidently a great part of the rain falling in a wooded country is 

 evaporated before it can flow off, as the roots of the trees retard its 

 collection in brooks and rivers. Lendenfeld has made some pre- 

 hminary computations which lead him to the conclusion that about 

 twenty-five per cent of the rain falling in wooded regions of the 

 temperate zone, such as central Europe, are due to the influence of 

 the forest. A country grown with grass and herbs would also 

 have more rain than one in which the bare rocks were exposed to 

 the air. 



In Australia the influence of the forest is entirely different from 

 what it is in Europe. The views of those Australians who are 

 principally interested in this matter are divided. The general opin- 

 ion is that the , climate is becoming dryer in consequence of de- 

 forestation. Others, however, maintain that the cutting-down of the 

 woods has no influence whatever upon the climate, and that, if 

 such an influence should exist, it is so small as to be of no account, 

 compared to the advantages connected with the deforestation. The 

 latter view is principally held by squatters and ranchmen, who, of 

 course, have an immediate interest in the opening of forest-land for 



agricultural and stock-raising purposes, and who cannot be expected 

 to be unbiassed. 



Australia is a very dry country, its northern portion alone being 

 exposed to tropical rains. Besides this, only the south-eastern part 

 is mountainous, which has elevations exceeding six thousand feet 

 in height. These elevations — the Australian Alps — materially 

 increase the amount of rain, and thus cause the great productivity 

 of the colonies of New South Wales and Victoria. 



Setting aside the Alps and the east coast, the whole of Australia 

 is very dry. The interior is almost rainless ; and even near the 

 coast, in the greater part of New South Wales and Victoria, the 

 amount of rain is very small, and does not reach the height of eight 

 inches, while the evaporation amounts to ten feet. In the interior, 

 rain is very rare, occurring only once in a period of about three 

 years. In countries where long-continued droughts prevail, such 

 plants as grow in humid regions cannot live. All plants of the 

 desert, and among them the trees, shrubs, and grasses of the 

 steppes of Australia, have certain means for increasing the water- 

 supply from the deeper layers of the soil (i.e., roots extending to 

 great depths), and others for diminishing evaporation. The stomata 

 of many Eticalypti are removed from the surface of the leaf, and 

 those of the Spinifex of the deserts are protected by a peculiar 

 arrangement. Leitgeb, who has studied the movability of the 

 cells of the stomata, found that they close the aperture the more, 

 the less the water at the disposal of the plant. 



Besides these well-known facts, Lendenfeld observed that the 

 stomata of the leaves of Eucalyptus are perfectly closed whenever 

 a hot and dry wind is blowing, so that in such cases no evaporation 

 to speak of takes place. Therefore the same wind which is so 

 dangerous to grasses and herbs has almost no influence whatever 

 upon the Eucalyptus trees. Furthermore, Lendenfeld concludes 

 that probably most plants of the desert have their stomata closed 

 during the day-time, while they are open during the night. It is 

 only then that carbonic acid enters the plant, and is dissolved in 

 the sap. In the morning they close the stomata, and assimilation 

 begins under the influence of the light. The carbonic acid dis- 

 solved during the night is decomposed, and the o,\ygen escapes 

 through the epidermis. 



It has been shown by Volkens, that during the latter part of the 

 night the atmosphere, even of the desert, is to a greater or less 

 degree saturated with vapor : therefore the plants do not lose 

 much water by opening their stomata at night. 



Almost all trees and shrubs of the interior of Australia produce 

 ethereal oils in great quantities. In evaporating, it lessens the 

 temperature of the leaves, and forms a layer of vapor all over the 

 forest. According to Tyndall, air saturated with ether is less per- 

 meable for radiant heat than ordinary atmospheric air : thus the 

 tree protects itself by means of a cover of ether from excessive heat 

 and evaporation. As the leaves of the Eucalyptus trees turn their 

 edges towards the sun, the effect of insolation is very slight. Thus 

 it is shown that the trees and shrubs of the arid parts of Australia 

 are well equipped to resist the dryness of the climate. 



But, besides these plants, numerous small grasses and herbs 

 occur, which Lendenfeld, following Volkens's example, calls ephem- 

 eric. They are not at all protected against evaporation. Their 

 roots do not penetrate the soil to any great depth, and their stomata 

 are open in the day-time. As their seeds are spread all over the 

 ground in great quantities, they grow up rapidly after every rain- 

 fall, and cover the bare ground with a fresh green. They are the 

 principal food of the sheep. 



As long as water remains in the upper layers of the soil, the 

 ephemeric plants grow. As soon, however, as the stock of water 

 is used up, they die, as their roots do not extend deep enough. 

 The roots of the trees spread from ten to fifteen feet below the sur- 

 face of the ground, and absorb all the humidity of these layers 

 which otherwise would gradually reach the surface in consequence 

 of capillary attraction. Thus they prevent the stock of deep water 

 from supplying the needs of the grasses. 



In all temperate and humid countries the struggle of the plants 

 is for light. In the interior of Australia, and in other similar sub- 

 tropical regions, they struggle for water. Thus the ephemeric 

 plants are here killed by the trees, and in wooded countries ihey do- 

 not occur at all. 



