352 



ARBDRETL'iM 



ARBORICULTURE 



the southern part yf t)iat state but all the West 

 Indies ami other tropical countries. 



A nalionnlizcd arborelum. 



The iirboretuin. tlierefore, worthy to be considered 

 national in scope and accomiilishment in a country of 

 such varied chinates a^ North .\inerica must consist of 

 a number of stations in tlilTerent parts of the country 

 under one nianasi'inent antl with one central head 

 from which the work of the ditTerent stations shoukl be 

 directed and superintended and which should be the 

 bureau of i)ublication of the results obtained in them. 

 The position of the central station in the country is of 

 little importance in comparison with its permanence, 

 endowment and freedom from all dangerous influences. 

 Such conditions of permanence and freeilom in this 

 country will best be obtained in connection with one of 

 the great endowed universities rather than with the 

 national or with any state government, for political 

 association is not conducive to the best scientific 

 research, and for the next hundred years at least, and 

 until a real knowledge of the vegetation of the earth 

 has been obtained, the National Arboretum must be 

 organized primarily for research. 



By the information it could acciunulate, such an in- 

 stitution would be able to aid the agricultural experi- 

 ment stations and state universities, which are the 

 natural and proper organizations for popularizing the 

 results of long-sustained scientific investigations, for 

 which they are not equipped and which, with the 

 uncertainty of their resources, they cannot hope suc- 

 cessfully to carry on. Forestry and landscape-garden- 

 ing are based on a knowledge of trees, and in the study 

 of trees are found pleasures which increase with knowl- 

 edge and endure through life. 



The Arnold .\rboretum endeavors to popularize its 

 knowledge by the publication of Bulletins of Popular 

 Information and by courses of popular field instruction; 

 and it should further be the duty of a national Arbo- 

 retum to aid in the establishment of arboreta in con- 

 nection with agricultural colleges and experiment sta- 

 tions, on the grounds of universities not equipped with 

 botanic gardens, and on the grounds of high-schools. 

 Collections of trees properly labeled are needed in 

 every institution of learning and in every large center 

 of population. Until such collections are established, 

 the people of the I'nited States can hope to know 

 little of the beauty and value of their native trees 

 and of those e.xotic trees which can safely be intro- 

 duced into different parts of the country. 



C. S. Sargent. 



ARBORICULTURE. Arboriculture is the growing or 

 cultivation of trees. It is distinct from sylviculture, 

 which grows trees in forest plantations for the pro- 

 duction of a timber-crop. Sylviculture is a part of 

 forestry. 



What constitutes a tree is not easy to explain in a 

 short and well-<lefined statement. A given species may 

 assume a tree-like habit or remain shrubby, according 

 to the climatic conditions, soil and other circumstances. 

 Usually a tree is defined, under normal conditions, as a 

 woody plant rising from the ground with a single stem 

 and attaining a certain height, fi.xed by some at 20, by 

 others at 1.5 feet, or c-ven less. A more exact definition 

 has been given by B. E. Fernow: "Trees are woody 

 plants the seed of which ha.s the inherent capacity of 

 producing natiirally within their native hmits one main 

 erect axis continuing to grow for a number of years 

 more vigorously than the lateral axes and the lower 

 branch's dying off in time." 



Trets are the mo.st proriinent feature of the vegetable 

 world and surj)as3 all other organic beings in hc-ight, 

 magnitude and longevity. The greatest height known 

 has been reachwi by iSequma Kempervirenii, which 

 attains 340 feet Not very far less is Eucalyptus nmyg- 



dalina, of which the highest tree actually measured is 

 given as 32.5 feet; it is, therefore, the tallest of the hard- 

 wood trees. The sequoias, however, are of more majes- 

 tic and gigantic appearance than the eucalyptus on 

 account of their massive trunk (see Scquuia). Pseu- 

 dolmiga taiifolia and Pinus Lambcrliana occasionally 

 attain 300 feet. A mmiber of other conifers, chiefly 

 American, grow to a height of 150 to 300 feet. Some 

 decitluous trees, as Plalanus occidentalis, several species 

 of oak and Liriodendron Tulipifera exceed 150 feet in 

 lieight. The jequitiba of southern Brazil (Couralari 

 Irqnlis, one of the Myrtaceie) is also a gigantic tree (see 

 Bot. Gaz. 31, p. 352). 



The greatest diameter has been observed in Caslanea 

 vesca, of which a tree with a partly decayed trunk at 

 the foot of Mt. Etna in Sicily measures more than 60 

 feet in diameter. After this the greatest diameter 

 observed is in Taxodium mucronnlum, about 40 feet, 

 and in Plalanus orientalis about the same, in Sequoia 

 gigatdea 35 feet, in Taxodium dislichum 30 feet, and 

 somewhat less in Adansonia digilala. 



The age attributed to many of the tallest trees is 

 based more or less on speculation, and opinions often 

 differ widely. Dracsena Draco is believed to reach 6,000 

 years of age, Adansonia digilala 5,000, Taxodium mu- 

 cronalum and Plalanus orientalis 4,000, Cupressus sem^ 

 pervirens and Taxus baccala 3,000, Caslanea saliva, 

 Qucrcus pedunculala, Sequoia giganlea and Cedrus 

 Libani more than 2,000 years. 



Although the trees are the most conspicuous features 

 of the vegetable kingdom, they represent only a small 

 percentage of it as regards the number of species. In 

 the United States, where about 600 trees occur, they 

 represent only about 3^ 2 per cent of the whole phanero- 

 gamic flora, in Eur<^e even less. As a rule, towards 

 the tropics the number of tree-hke species increases, 

 towards the arctic regions it decreases. Remarkably 

 rich in trees is the flora of Japan, where the proportion 

 of trees to the whole phanerogamic flora is more than 

 10 per cent, which percentage surpasses by far that of 

 any other country in the temperate regions. 



Trees belong to many different natural orders, but of 

 the orders of monocotyledonous plants only a few con- 

 tain trees and none of them is hardy North. None of the 

 larger orders contains trees only, but there are some 

 which consist exclusively of woody plants and include 

 a large proportion of trees, as Pinacea?, Fagaceae, 

 Salicaceae, Juglandaceae, Magnohacea-, Sapindaceae, 

 Eteagnaceae, Ulmacese, Hamamelidacese, Laiu-aceae, 

 Anacardiaceae, Ebenacese, Styracaceae and others. 



The uses of trees are manifold, and a country from 

 which the forests have been destroyed becomes almost 

 uninhabitable and worthless to mankind. The forests 

 furnish wood and timber, exercise beneficial influences 

 on the climate, act as regulators of the waterflow, pre- 

 vent erosion and also the removal of soil by the wind. 

 Besides furnishing wood and timber, many trees yield 

 other products of great economic importance, especially 

 the numerous kinds bearing fruits. The icsthetic value 

 also of the tree must not be underrated, although it 

 cannot be counted in money. 



The science of trees and shrubs is dendrology. The 

 art of growing trees is arboriculture, while the rearing 

 and maintaining of forests and the production of 

 timber-crops is sylviculture. Arboriculture is some- 

 times used in a broader sense, like dendrology, to in- 

 clude also the growing of shrubs. Orchard culture is a 

 branch of arboriculture or of horticulture, and deals 

 with the cultivation of fruit trees; it is usually included 

 under pomology, which comprises both the science and 

 practice of fruit-growing, 



As ornamental subjects, trees are more permanent, 

 easier of cultivation and cheaper in the long run than 

 herbs. It is curious to note how little attention the 

 average gardener who has the care of a park or garden 

 gives to the most prominent feature of his domain. He 



