348 JOUKNAL OF THE KOYAL HOETICULTUEAL SOCIETY. 



but the Pampas thistle is often higher than the crown of the rider's 

 head." * 



Mr. Darwin calls it a thistle as distinct from the cardoon ; but 

 neither Hooker nor Griesbach appears to recognize any species of Carduus 

 or Gnicus. The latter botanist speaks only of the cardoon (Cynara 

 Gardunculus), Silybum, Lappa (Burdock), and fennel ; Silybum Marianum, 

 known as the milk-thistle, is the only species of so-called " thistle " 

 indigenous in the Mediterranean regions and further east. It is closely 

 allied to Carduus, the true thistle, so that perhaps Darwin referred to 

 this plant. It has white streaks on the ribs and veins of the leaves. 



It is an interesting fact that with regard to the evident dispersion 

 of our British plants, those which have travelled furthest and established 

 themselves most thoroughly are self-fertilized plants, with the exception 

 of a few anemophilous plants, as Bumex crispus, Luzula campestris, 

 plantains, and a few grasses. In my essay on " The Self-fertilization 

 of Plants " f I have enumerated about thirty natural orders which are 

 represented in at least, but often many more than, four distinct localities. 

 I will select a few familiar examples. 



Gapsella Bursa-pastoris (Shepherd's Purse). — Chili ; New Z. ; Trop. 

 Asia ; N.E. Afr. ; S. Ausfcr. ; Hongk. ; Jap. ; Kamchat. 



Stellaria media (Chickweed). — Auckland, Campbell, and Kerguelen 

 Islands ; New Z. ; Trop. Asia ; Madeira ; S. Afr. ; S. Amer. ; S. Austr. ; 

 Hongk. ; Jap. / 



Galium Aparine (Cleavers). — Chili ; S. Austr. ; Falkland and Luegia ; 

 New Z. ; N.E. Afr. ; Jap. ; Madeira ; Mexico. 



Solarium nigrum (Black Nightshade). — S. Austr. ; Tasm. ; New Z. ; 

 N.E. Afr. ; Society I. ; Andaman I. ; Hongk. ; Jap. ; Calif. ; Galapagos I. 



Polygonum aviculare (Knotgrass). — S. Austr. ; New Z. ; S. Afr. ; 

 S. Amer. ; N.E. Afr. ; N.E. Asia ; Jap. 



The above is but a sample ; but the inference is conclusive that for 

 securing the sole "end" of plant-life (that is, means of propagation 

 whether by buds or seeds), self -fertilizing plants are much better favoured 

 than those which are entirely or mostly intercrossed. $ 



Examples of self- and wind-fertilized plants, acquiring great vigour 

 when naturalized abroad, often replacing the native vegetation, are given 

 in New Zealand. Mr. W. T. Locke Travers, writing to Sir J. D. Hooker 

 from Canterbury in 1864, thus speaks of some of our British weeds : 



" You would be surprised at the rapid spread of European and other 

 foreign plants in this country. All along the sides of the main lines 

 of road through the plains, the knotgrass (Polygonum aviculare) grows 

 most luxuriantly, the roots sometimes two feet in length, and the plants 

 spreading over an area from four to five feet in diameter. The dock 

 (Bumex crispus) is to be found in every river bed, extending into the 

 valleys of the mountain rivers until these become mere torrents. The 

 sowthistle is spread all over the country, growing luxuriantly nearly up 



* Nat. Voyage, &c, p. 148. f Trans. Linn. Soc. 1877. 



X The reader will find this contention fully established in the paper alluded to. 

 Darwin's original statement that " Nature abhors self-fertilization " was based upon 

 his study of relatively large and conspicuous flowers ; but insignificant blossoms of 

 " weeds " and their profuse multiplication proves the above to have been a mistake, 

 which indeed Darwin subsequently acknowledged. 



