ADDRESS. bciii 



Dr. Hooker Instances certain species of Coprosma, of Celmisia, and a kind 

 of Australian Fern, the Lomaria procera, which have undergone such striking 

 changes in their passage from one portion of the Great Pacific to another, 

 that they are scarcely recognizable as the same, and have actually been re- 

 garded by preceding botanists as distinct species. But he does not state 

 that any of these plants have ever been seen beyond the above-mentioned 

 precincts ; and yet if Nature had not imposed some limits to their suscepti- 

 bility of change, one does not see why they might not have spread over a 

 much lai^er portion of the earth, in a form more or less modified by external 

 circumstances. 



The younger DeCandolle, in his late admirable treatise already referred 

 to, has enumerated about 117 species of plants which have been thus dif- 

 fused over at least a third of the surface of the globe ; but these apparently 

 owed their power of transmigration to their insusceptibility of change, for 

 it does not appear that they have been much modified by the effect of climate 

 or locality, notwithstanding the extreme difference in the external conditions 

 to which they were subjected. 



On the other hand, it seems to be a general law, that plants, whose organi- 

 zation is more easily affected by external agencies, become, from that very 

 cause, more circumscribed in their range of distribution ; simply because a 

 greater difference in the circumstances under which they would be placed 

 brought with it an amount of change in their structure, which exceeded the 

 limits prescribed to it by Nature. 



In short, without pretending to do more than to divine the character of 

 those impediments, which appear ever to prevent the changes of which a 

 plant is susceptible from proceeding beyond a certain limit, we seem to catch 

 a glimpse of a general lavv^ of Nature, not limited to one of her kingdoms, but 

 extending everywhere throughout her jurisdiction, — a law, the aim of which 

 may be inferred to be, that of maintaining the existing order of the universe, 

 without any material or permanent alteration, throughout all time, until the 

 Jiat of Omnipotence has gone forth for its destruction. 



The will, Avhich confines the variations in the vegetable structure within a 

 certain range, lest the order of creation should be disturbed by the introduc- 

 tion of an indefinite number of intermediate forms, is apparently the same in 

 its motive, as that which brings back the celestial Luminaries to their ori- 

 ginal orbits, after the completion of a cycle of changes induced by their 

 mutual perturbations; it is the same which says to the Ocean, Thus far 

 shalt thou go, and no further; and to the Winds, Your violence, however 

 apparently capricious and abnormal, shall nevertheless be constrained within 

 certain prescribed limits — 



Ni faciat, maria et terras coelumque profundum, 

 Quippe ferant rapidi secum, verrantque per auras. 



The whole indeed resolves itself into, or at least is intimately connected 

 with, that law of symmetry to which Nature seems ever striving to confirm, 

 and which possesses the same significance in the organic world, which the law 

 of definite proportions does in the inorganic. 



It is the principle which the prophetic genius of Goethe had divined, long 

 before it had been proved by the labours of physiologists to be a reality, and 

 to which the poet attached such importance, that the celebrated discussion 

 as to its merits which took place in 1820 between Cuvier and Geoffrey St. 

 Hilaire so engrossed his mind, as to deprive him, as his biographer informs 

 us*, of all interest in one of the mostportentous political events of modern days 



* Lewes' Life of Goethe, vol. ii. 



