162 



KNOWLEDGE. 



[July 1, 1897. 



leaves, in which the secretion is highly aromatic and of 

 an oily or resmous nature, has gained for gum trees the 

 reputation of being of great hygienic value in malarious 

 countries. How far the action is direct, and how far 

 merely indirect, is uncertain ; but there is no doubt that 

 beneficial results have been attained by planting gum trees 

 in marshy, unhealthy districts. A striking point in which 

 the species of gum trees differ from each other is afforded 

 by tlie barli. In some it is clean, smooth, polished, and 

 permanent, as in our native beech ; in others it is 

 deciduous — that is, it flakes off, as in the plane tree, but 

 usually in much thicker layers, and in large pieces. 

 Formerly, the Australian aborigines used the bark thus 

 thrown off to construct the only kind of shelter they 

 enjoyed, and many names have been given locally to several 

 species on account of differences in the bark. Especially 

 remarkable among the smooth-barked species is the karri 

 (Eucah/ptiis Jiversicolnr) of Western Australia, whose 

 columnar trunks are often branchless to a height of one 

 hundred and fifty to three hundred feet, and taper so 

 gradually that they appear of the same diameter through- 

 out. The paintings of Australian vegetation in the North 

 Gallery at Kew give a good idea of gum tree forests, and 

 also of individual trees. 



Having described the structure of the flowers, I will now 

 describe some of the many modifications of the fruit or 

 seed-vessel. Like so many other Australian fruits, it is 

 of a woody nature in all of the species, and sometimes 

 excessively hard, in a comparatively early stage. Returning 

 to the blue gum, the flower of 

 which has already been described 

 and illustrated, we have a fruit of 

 medium size. This species is the 

 one most widely planted on account 

 of its supposed febrifugal proper- 

 ties, and the one most likely to 

 come under the notice of inhabi- 

 tants of northern latitudes, where 

 —in the western counties of the 

 United Kingdom for example — it 

 withstands all but exceptionally 

 severe winters, and therefore 

 attains a considerable size. Of 

 course no prudent person would 

 think of planting it in this country 

 It is a native of Victoria, Tas- 

 mania, the islands of Bass's Straits, and the southern 

 part of New South Wales ; but there are probably more 

 blue gum trees now planted in other countries than 

 exist in their Australian home. The blue gum tree is in- 

 valuable in subtropical or temperate regions where there is a 

 small rainfall. Taking into consideration the comparatively 

 short period — less than a century— that this tree has been 

 known, and that it is less than half a century that its value 

 has been recognized, no one tree has such an extensive 

 literature. Sir F. von Mueller, who devotes much more 

 space to it than to any species of Kucah/iitus in his 

 " Eucalyptographia," cites nearly a hundred different books 

 and articles devoted to it ; and lie himself says : " It is not 

 too much to assert that among rather more than one 

 thousand different species of trees indigenous in Australia, 

 Eucalyptus i/lohulus takes the first position." Though not 

 the tallest of the gum trees, individuals have been measured 

 in Tasmania up to three hundred and thirty feet high, or 

 more than twice the height of the conspicuous Douglas 

 pine flagstaff' in Kew Gardens. In strikmg contrast to 

 the hard-wooded trees of the northern hemisphere, this 

 and other species of Kttralyptus grow very rapidly, and it 

 has been estimated that a forest of marketable timber can 



Flfl. l.^Seed-vessel or 

 Fruit of the Blue Gum, 

 JSucahiptns gloluUis. 

 Natural size. Original 

 di awing. 



for profitable purposes. 



Fio. 2.— Cluster of Seed- 

 vessels of Ettcaliiptus 

 amiiddalina, Natural size. 

 Original drawing. 



be grown in thirty or forty years. This is borne out by 

 facts near home, as, for instance, in the lake district of 

 Italy, and in the malarial swamps near Rome, where trees 

 have attained a height of one hundred to one hundred and 

 twenty feet in less than thirty years. 



Comparing the seeds of these gigantic trees with those 

 of our forest trees, such as the 

 oak or the beech, we are surprised 

 at the exceedingly large number 

 and the smallness of their size. 

 In place of the solitary seed 

 produced by each flower of the 

 oak, we have a seed-vessel divided 

 into four or five compartments, 

 each containing a number of seeds 

 varying in size in different species 

 from one-twentieth to three- 

 fourths of an inch in length. 

 Even the longest ones are very 

 slender. The seeds of the blue 

 gum are about one-tenth of an 

 inch long, and it takes about ten 

 thousand fertile ones to weigh 

 an ounce. They differ as much 

 in shape as they do in size ; and 

 what is more remarkable, by far 

 the larger number in each seed- 

 vessel are sterile, and differ in 

 shape from the fertile ones. The 

 latter retain their vitality for 

 several years — some species for 

 at least a dozen years — and this 

 property, together with their smallness, renders it easy to 

 introduce the gum trees into the most distant countries. 



To illustrate the variety offered by the seed-vessels of 

 the gum trees I have had figures drawn of a few of the 

 most diverse forms. The smallest known to me is that of 

 E. crebra, a species ranging from the shores of the Gulf of 

 Carpentaria to Port Jackson in New South Wales, which has 

 a fruit about an eighth of an inch in diameter. It is a tree, 

 sometimes one 

 hundred feet high, 

 having extremely 

 slender ultimate 

 branchlets. Rut 

 I have selected the 

 more noteworthy 

 E. amygdalina to 

 represent the small 

 fruited species. 

 This inhabits the 

 colonies of New 

 South Wales, Vic- 

 toria, and Tasma- 

 nia, and, as Mueller 

 says, " is one of 

 the most remark- 

 able trees in the 

 whole of creation." 

 I cannot do better 

 than quote from 

 him, as he wrote 

 from personal 

 obser vat i on: — 

 " Viewed in its 

 marvellous height, 



when standing forth in its fullest development, on the slopes 

 or within glens of mountain forests, it represents probably 

 the tallest of all trees of the globe. Considered as a hardwood 



Fio. 3. — Cluster of Seed-vessels of Fucah/pius 

 cornula. Natural size. Original drawing. 



