November 29, 1894] 



NATURE 



i'7 



However this may be, we know trees succumb to external 

 luses. Nevertheless, they are perennial enough to outlive 

 ;.ight else, " to be the oldest inhabitants of the globe, to be 

 more ancient than any human monument, and exhibit in some 

 of the survivors a living antiquity compared with which the 

 mouldering relics of the earliest Egyptian civilisation, the pyra- 

 mids themselves, are but structures of yesterday. ' The dragon 

 'rees, so called, found on the island of Teneriffe, off the African 

 oast, are believed to be many thousand years old. The largest 

 ., only 15 feet in diameter and 75 feet high. Our sequoias are 

 lore rapid growers, and attain in 3000 to 4000 years, which 

 ii.ay be the highest age of living ones, more than double these 

 i.mensions. 



While this persistence of life is one of the attributes which 

 in the battle for life must count of immeasurable advantage, 

 ihe other characteristic of arboreal development, its elevation 

 in height above everything living, is no less an advantage over 

 x\\ competitors for light, the source of all life. Can there be 

 ny doubt that in this competition size must ultimately triumph, 

 ,ind the undersized go to the wall ? 



Endowed with these weapons of defensive and offensive war- 

 'are, forest growth, through all geologic ages during which the 

 •arth supported life, has endeavoured, and no doubt to a degree 

 succeeded, in gaining possession of the earth's surface. 



As terra Jlrma increased emerging in islands above the ocean, 

 so increased the area of forest, changing in composition to 

 irrespond with the change of physical and climatic conditions. 

 .\3 early as the Devonian age, when but a small part of our 

 -mtinentwas formed, the mud flats and sand reefs, ever in- 

 casing by new accumulations under the action of the waves 

 .nd currents of the ocean, were changed from a bare and 

 ifeless world above tide level to one of forest-clad hills and 

 Inles. 



Not only were such quaint forms as the tree rushes Calamites, 



I.ei.idodendron and Sigillaria present, but the prototype of our 



ine, the Dadoxylon, had made its appearance. 



The same class of flowerless plants known as vascular 



lyptogams, with the colossal tree ferns added, became more 



umerous and luxuriant in the Carboniferous age, as well as the 



lowering .Sigillaria and coniferous Dadoxylon. This vegetation 



,irobibly spread over all the dry land, but the thick deposits 



if vegetable remains accumulating in the marshy places under 



i^nse jungle growth and in shallow lakes with floating islands, 



ere tinally, in the course of geologic revolutions, turned into 



lie great coal fields. 



In those and subsequent geologic times some of the floral 

 ypes vanished altogether and new ones originated, so that at 

 '.t; end of Mesozoic times a considerable change in the land- 

 j.ipe had taken place. 



In addition to coniferous trees, the palms appeared, and also 

 the first of angiosperms, such as the oak, dogwood, beech, 

 "■plar, willow, sassafras, and tulip tree. Species increased in 

 imbers, adapted to all sorts of conditions ; the forest in a most 

 ..uied and luxuriant form climbed the mountain-sides to the very 

 crests, and covered the land to the very poles with a flora of 

 tropical and semi-tropical species. 



Then came the levelling process and other changes of post- 

 Tertiary or Quaternary times ; the glaciation of lands in 

 northern latitudes, with the consequent changes of climate, 

 which brought about corresponding changes in the ranks of the 

 forest, killing out many of the species around the north pole. 

 Only the hardier races survived, and these were driven south- 

 ward in a veritable rout. 



When these boreal times subsided in a degree, the advance 

 of the forest was as sure as before, but the battle order was 

 somewhat changed to suit the new conditions of soil and 

 climate. Only the hardiest tribes could regain the northernmost 

 posts, and these found their former places of occupancy changed 

 by fluvial and lacustrine formations and the drifts borne and 

 deposited by the ice-sheets, while some by their constitution 

 were entirely unfitted from engaging in a northern campaign, or 

 found insurmountable barriers in the refrigerated east-west 

 elevations of Europe and Western Asia. 



In addition, there had come new troubles from volcanic erup- 

 tions, which continually wrested the reconquered ground from 

 \he persistent advance guards of the arboreal army, annihilating 

 them again and again. 



Finally, when the more settled geologic and climatic con- 

 ditions of the present era arrived, and the sun rose over a 

 world ready for human habitation, man found what we are 



NO. 1.^09, VOL. 5 l] 



pleased to call the virgin forest — a product of long- continued 

 evolutionary changes — occupying most, if not all the dry land, 

 and ever intent upon extendmg its realm. 



This prehistoric view of the battle of the forest cannot be left 

 without giving some historic eviilences of its truth. 



Not only have palaeobotanists unearthed the remnants of the 

 circumpolar flora, which give evidence that it resembled that of 

 present tropic and semi-tropic composition, but they have also 

 shown that sequoias, magnolias, liquidambars and hickories- 

 existed in Europe and on our own continent in regions where 

 they are now extinct. We have also evidences of the repeated 

 successes and reverses of the forest in its attempts to establish 

 itself through long geologic transformations. 



One of the most interesting evidences of these vicissitudes in 

 the battle of the forest is represented in a section of Amethyst 

 .Mountain in Yellowstone National I'ark, exhibiting the remains 

 of fifteen forest growths, one above the other, buried in the 

 lava. Again and again the forest subdued the inhospitable ex- 

 coriations ; again and again it had to yield to superior force. 



Among these petrified witnesses of former forest glory, mag- 

 nolia, oak, tulip tree, sassasfras, linden and ash have been iden- 

 tified, accompanying the sequoia in regions where now only the 

 hardiest conifer growths of pines and spruces find a congenial 

 climate. 



As the forest formed and spread thus during the course of 

 ages, so does it form and spread to-day, unless man, driven by 

 the increasing needs of existence, checks its progress and reduces 

 its area by the cultivation of the soil. This natural extension 

 of the forest cover or afforestation takes place readily when- 

 ever soil and climate is favourable, but it is accomplished 

 just as surely, though infinitely slower, in unfavourable situa- 

 tions. On the naked rock, the coarse detritus and gravel beds, 

 on the purely siliceous sand deposits of river and ocean, or in 

 the hot dry plains, the preliminary pioneer work of the lower 

 vegetation is required. .A.lgie, lichens, mosses, grasses, herbs, 

 and shrubs must precede to cultivate the naked rock, to mellow 

 the rough moisture by shading the ground, and gradually render 

 it fit for the abode of the forest monarch. The army of soil- 

 makers and soil-breakers, the pioneers, as it were, of the forest, 

 are a hardy race, making less demands for their support than 

 those that follo«-. They come from different tribes, according 

 to the soil conditions in which they have to battle. 



The aspen [Popiihis tremuloides) is one of these forerunners, 

 which is readily wafted by the winds over hundreds of miles, 

 re.adily germinates and rapidly grows under exposure to full 

 sunlight, and even now in the Rocky Mountains and elsewhere 

 quickly takes possession of the areas which man has ruthlessly 

 destroyed by fire. This humble and ubiquitous, but otherwise 

 almost useless, tree is nature's restorative, covering the sores and 

 scalds of the burnt mountain side, the balm poured upon 

 grievous wounds. Though short-lived, with its light summer 

 foliage turning into brilliant golden autumn hues, it gives 

 grateful shade and preserves from the thirsty sun and wind some 

 moisture, so that the better kinds may thrive and take its place 

 when it has fulfilled its mission. 



One of the shrubs or half-trees which first take possession of 

 the soil in the western mountain country is the so-called moun- 

 tain mahogany [Ccreocar/iis h-dif alius), covering the bared 

 slopes after the lire has killed the old timber. 



In other regions, as on the prairies of Iowa and Illinois, hazel 

 bushes, or in the mountains of Pennsylvania and the .\lleghanies 

 in general, ericaceous shrubs like the laurel and rhododendrons 

 or hawthorn, viburnum and wild cherry are the first comers, 

 while along water-courses alders and willows crowd even the 

 water into narrower channels, catching the soil which is washed 

 from the hill sides and increasing the land area. 



One of the most interesting soil-makers, wresting new terri- 

 tory from the ocean itself, is the mangrove along the coast of 

 Florida. Not only does it reach out with its aerial roots, entang- 

 ling in their meshes whatever litter m.iy float about, and thus 

 gradually building up the shore, but it pitches even its young 

 brood into the advance of the battle, to wrestle with the waves, 

 and gain a foothold as best it may. 



Not less interesting in this respect is that denizen of the 

 southern swamp, the bald cypress, with its curious root excres- 

 cences known as cypress knees, which, whatever their physio- 

 logic signilicance, are most helpful in expediting changes of 

 water into land sufficiently dry to be capable of supporiiiig the 

 more fastidious species in regard to moisture and conditions. 



On the dry hot mesas, and in the arroyos of the south-'western 



