I62 



NA TURE 



[June 15, 189^ 



The plants which have become naturalised in Australia natur- 

 ally come under two headings, viz. those purposely introduced for 

 use, ornament or sentiment, and those which accidentally found 

 their way here. 



Of those introduced for use or for ornamental purposes, a 

 large number do not spread to any extent : they aie children of 

 civilisation and show no tendency to become feral. Many 

 hardy annual garden flowers come up self-sown in gardens year 

 after year and yet never gain a footing outside. Others again, 

 which have the power of spreading rapidly, are never able to 

 do so, as they are succulent feed, and cattle take care thit they 

 never multiply. Such are oats and other grains. Wheat never 

 seems to spread at all away from the fields in which it is culti- 

 vated. But still t ere are numbers of useful plants which are 

 able to hold their own and more. Among these may be men- 

 tioned the lemon, peach. Cape gooseberry, tomato, and passion 

 fruit, all of which are wild in many parts of the Illawarra 

 district, and continue to bear fruit. Another species of passion 

 flower {Passiflora alhaf) is common theie and is even more 

 plentiful than the edible species. It is bitter and naueous, but 

 has spread over large tracts of bush country, converting them 

 into tangle of the densest description. The common bramble 

 or blackberry has been introduced for th; sake of its fruit, and 

 is now beginning to be a troublesome tenant of unoccupied 

 lands in the cooler parts of the Colony. It reaches a develop- 

 ment far exceeding that attained in its native land. 



Sweet-briar and Scotch thistles are said to have been intro- 

 duced fjr the sake of the associations clustered round the plants 

 in the mother country. The latter plant is reported to have 

 been introduced into Tasmania by a patriotic Scotchman 

 desirous of having his national plant growing near his new 

 home. lie appears by all accounts to have succeeded only too 

 well. 



Bat wiih regard to most introduced plants, there is much 

 difficulty in discovering the method of introduction. The 

 plants which habitually flourish in European cornfields are 

 certainly ea;ily accounted for — they came in the seeds imported 

 to the Colonies. Such are corn marigold, c >rn spurrey, and 

 many of the Caryophylleje, the cornfield poppy and numerous 

 others which will occur to every one. Then again, many 

 noxious weeds growing among grain, were introduced to Aus- 

 tralia in straw in packing cases. Such are the Centaureas and 

 others. As an example of this I may note that Buplcurum 

 rotttndifolium first appeared in the Mudgee District in a yard 

 where a box from Kngland was unpacked. 



But with many plants introduced, we can only reason by 

 analogy as to the manner of their introduction. In an article 

 on the weeds of Europe in the Cornhill Magazine, an anony- 

 mous writer states that a com-non En'4;lish weed was introduced 

 into an Antarctic island by the use of a spade which had some 

 mould attached to the blade, and the plant has now spread all 

 over the island. Darwin gives instances of seeds being found 

 in balls of clay attached to the feet of birds, and even to the 

 elytra of beetles. Still, the method of introduction of many 

 foreign weed; must in the nature of things always remain more 

 or less of a mystery. Many aliens have arrived in the colony 

 attached to the wool of sheep or the hair of other animals as in 

 the case of the Bathurst Burr — a species of vegetable stowaway. 

 As to the methods of spreading, they are various. Cultiva- 

 tion of the soil brings the weeds in its wake, and they manage 

 to spread somehow. S ime have specially constructed seeds 

 to float through the air — any one who has seen thistle-infested 

 country on a windy day will have a good idea how thistles 

 spread. The Composites are especially rich in plants adopting 

 this contrivance. Others stick to the wool and hair of animals 

 by hooks, barbed hairs, or sticky glands. Others again have 

 seeds so minute that a high wind will carry them, although they 

 are not furnished with spicial apparatus for the purpose. 



Railways and roads are active helpers in the dissemination of 

 aliens, especially the former. The land being fenced in is 

 protected from the depredations of stock, and thus protected 

 the weeds flourish and spread rapidly. In 1887 I remember 

 noticing on the Mudgee Railway near Lue that there were 

 miles of the embankments one tangled mass of Meliotus parvi- 

 Jlorus. And in the neighbourhood of Bowenfels the railway 

 line enclosures are thickly covered with a species o{ Ilypochccris : 

 it is pretty plentiful outside but inside the land is a golden sheet 

 of the yellow flowers. Rivers also act in the same way, and 

 especially carry weeds when in flood an 1 deposit them on the 

 fljoded Ian Is. I first noticed Ranunculus muiicatus and Fool's 



parsley on the river banks at Mudgee. The following year 

 they had reached CuUenbone, and the next year had got as far 

 as Gunta.vang, a distance of seventeen miles by ro.id but at 

 least twonty-five or thirty by the river. A curi us instance of 

 the spread of a plant from one locality to another was afforded 

 me in 1886 and 1887. During a journey from Guntawang to 

 Wellington, a distance of forty-two miles, I noticed at Welling- 

 ton, on the river banks, great quantities of Cassia sophorn. At 

 that time none of the plant was found in the Mudgee District, 

 but in the same year a mail coach commenced running from 

 Wellington to Gulgong passing through Gunlawang. The 

 following year, two plants of the Cassia appeared at Gunta- 

 wang, and soon after it began to be common in the district. 

 The Rev. Dr. Woolls, at a meeting of the Linnean Society of 

 N.S Wales, in September 1890 exhibited plants of Catotis 

 scapigera a'ld C hispiihda from Concord and Burwood. These 

 are strictly denizens of the interior and were probably brought 

 down by sheep travelling to the sale yards. Indeed I feel 

 pretty sure that an examination in the neighbourhood of the 

 Homebush sale yards would show that many western plants are 

 brought down by the sheep, etc. In collecting introduced 

 plants, I have always been most successful by roadsides, river- 

 banks, and railway enclosures, and there can be no doubt but 

 that they are the principal lines of travel for these plants. 



The plants which hive edible fruits containing indigestible 

 seeds are for the most part dispersed by birds and mammals 

 which eat the fruit and void the seeds in new localities. In 

 this way passion fruit, blackberries, Phylolaua, tonia'oes, 

 solanums, Cape gooseberries, and many others are distributed. 



It is a significant fact that horehound — Marruhrium — is 

 always plentiful in the vicinity of a sheep station. Two other 

 plints commonly found in the same situation are the introduced 

 nettles, Urtica urens and U. dioica, whether from the plants 

 being ealen by the sheep and the undigested seeds voided, or 

 because that in sheep-manured land they find a c mgenial soil, 

 I am unable to say. 



Australian plants from their long isolation, and their having 

 little competition of a severe kind, settled down into a 

 state of balance or rather of slight oscillation, governed by a 

 few causes, which themselves varied but little. In the older 

 continents, however, from the intercommunication of the various 

 nations, and from the fact that men continually add to ;heir 

 stock of cultivated plants, there is severe competi'ion ; the 

 struggle for existence goes on continually and aided by natural 

 selection and domestication some plants gain an advantage. 

 Among other, useful habits acquired by plants under com- 

 petition is a certain plasticity of constitution which enables them 

 to bear changes to diflferent climates with equanimity. On this 

 account the old world weeds when brought to Australia are able 

 to beat the native plants. They are mostly plain dwellers, and 

 as such accustomed to the heat of the sun in the open, and the 

 bitter blasts of the winter, better than forest plants. When 

 forests are cleared and brought under cultivation, the weeds 

 soon beat the former occupants cut of the field. Again 

 many old world weeds are plants of wide range, and on this 

 account have an advantage over those of more restricted habitat. 

 " Widely varying species abounding in individuals which have 

 already triumphed over many competitors in their own widely 

 extended homes, will have the best chance of seizing on new 

 places when they spread into new cotmlries. In their new 

 homes they will be exposed to new conditions, and will 

 frequently undergo further modification and improvement; and 

 thus they will become still further victorious and produce groups 

 of modified descendants." ("Origin of Species," 6ihed. p. 319) 

 As before remarked their success in competition implies a 

 plasticity of organism which is an advantage to them also ; on 

 this subject Darwin says, " If a number of species, after having 

 long competed with each other in their old home, were to 

 migrate in a body into a new and afterwards isolated country, 

 they would be little liable to modification or variation ; for 

 neither migration nor isolation in themselves effect anything. 

 (Op. cit., p. 319.) The isolated productions of Australia 

 00 the other hand, have had uniform conditions and com- 

 paratively small range and so jthey cannot make way against 

 those that have had such competition and range. 



"In the same manner at the present day, we see that very 

 many European productions cover the ground in La Plata, New 

 Zealand and to a lesser extent in Australia and have beatrn the 

 natives, whereas extremely few southern forms have come to be 

 naturalised in any yiart of the northern hemisphere, though 



NO. 1233, VOL. 48] 



