246 



The same thing has happened with Dianllms brack ijanthus, Boiss. et Rent., which Xatar and Maill 

 took to be D. attemiatus, Benth., in the Pyrenees, and Koch for D. virgineus ; such mistakes being due to 

 the modifications produced by varying elevations. In some cases the very same organs become atrophied 

 or disappear, while in others they become much more developed than usual.* 



2. The especially characteristic features of alpine plants, as compared with similar or allied jjlants 

 growing at lower levels, are a dwarfing in size and compactness of growth, sometimes giving rise to a 

 moss-like appearance; a more intense green colour in the leaves, and greater brilliancy and size in the 

 flowers ; an increased hairiness of the leaves, and occasionally a certain degree of fleshiness of the tissues.! 

 Now, by growing lowland plants at high altitudes, Bonnier,! Flahault,§ and others have shown that such 

 characters as these may be rapidly acquired. For instance, Bonnier made observations on Teucrium 

 Bcorodonia for no less than eight years, and he found that this plant, when sown at a high situation in 

 the Pyrenees, produced very short aerial stems, with more hairy and darker green leaves, and more 

 compact inflorescence. On the other hand, seeds gathered from plants growing at high altitudes, and 

 sown in Paris, after three years produced elongated stems, with less hairy and brighter green leaves, or 

 plants very similar to those from seeds obtained in the neighbourhood of Paris.|| 



3. Existing floras exhibit only one moment in the history of the earth's vegetation. A transfor- 

 mation which is sometimes rapid, sometimes slow, but always continuous, is wrought by the reciprocal 

 action of the innate variability of plants, and of the variability of the external factors.H 



And again : — 



4. There are, further, some species — and this fact is as important to the .systematist as to the 

 physiologist — which adapt themselves to the varying conditions of humidity so completely that their 

 extreme forms appear to belong to different species, but these by a change in the supply of moisture may 

 pass over into one another.** 



5. Every plant .... occupies its place in the order of nature by the action of two forces — 

 the inherent constitutional life-force with all its acquired habits, the sum of which is heredity ; and the 

 numerous complicated external forces or environment. To guide the interaction of these two forces 

 . . . . is, and must be, the sole object of the breeder, whether of plants or animals.ft 



6. The combination and interaction of these innumerable forces embraced in heredity and environ- 

 ment, have given us all our bewildering species and varieties, none of which ever did or ever will remain 

 constant. J J 



7. Bringing a species into a new environment disturbs its fixity. Rich soil especially gives rise to 

 variations in growth which seems to be new, and by repetition become inherently fixed. Sometimes 

 ancestral states are brought about by good soil ; sometimes (perhaps oftener), also by starvation ; neiv 

 variations oftenest by rich soil and general prosperity.§§ 



Variation is going on noio. 



Authors sometimes argue in a circle when they state that important organs never vary ; for these 

 same authors practically rank that character as important (as some few naturalists have honestly confessed) 

 which does not vary ; and, under this point of view, no instance of an important part varying will ever 

 be found ; but under any other point of view many instances assuredly can be given.|||| 



And again : — 



I will add another remark : Naturalists continually assert that no important organ varies ; but in 

 saying this they unconsciously argue in a vicious circle ; for if an organ, let it be what it may, is highly 

 variable, it is regarded as unimportant, and under a systematic point of view this is quite correct. But as 

 long as constancy is thus taken as a criterion of importance, it will, indeed, be long before an important 

 organ can be shown to be inconstant.lill 



* Origin of Plant Structures. Henslow, \V2. 



t Compare, also, in this connection, my A second contribution toicards a Flora of Mt. Kosciiislo, Arjric. GazMe, 

 N.S.W., Oct., 1899. 



+ Ann. Sci. Nut. Bot., vii si^rie, xx, p. 217, 1894. § Ann. Sci. Xat. Bot., p. 159, 1879, and Rev. Gen. de Bot., 



ii, p. .51.3, 1891. \\ Variation in Aniviah and Plants. H. M. Vernon, p. 311. "i Plant Geography. Schimper, p. v. 



*''/4. p. 3. ff Fundamental Principles of Plant Breedinff. L. Burbank, p. i. J J /6. p. 3. %^ Some experimc7its 



of Luther Burbank. V>. S. Jordan, p. 205. Ill] Origin of Species. Darwin, p. 46. HH Animals and Plants under 



Domestication. Darwin, vol. i, p. 359. 



