522 On the Dispersion arid 



fins ciliated on the margins ; and the ultimate joint terminated, 

 besides, with four similar appendages, and a triangular pro- 

 cess between them. 



The large segment is, in some specimens, smooth and even ; 

 but in others, one of which was selected for our figure, it is 

 raised at the top into two oval bosses that greatly resemble 

 the elytra of a Meloe, and are beautifully punctured. The 

 same parts are visible on the ventral surface in both varieties, 

 but much smaller in that whose back is smooth. Jt may be a 

 sexual distinction. 



George Johnston, M.D. 

 Berwick upon Tweed, April 18. 1832. 



Art. VII. On the Dispersion and Distribution of Plants* 

 By J. E. L. 



If we take a general view of the surface and covering of 

 the earth, we shall meet with a perpetual series of flowery 

 valleys, mountains rich in alpine verdure, and forests smiling 

 with the bright and luxuriant tints of the tropics ; or sternly 

 resisting, with their dark and sombre foliage, the frozen winds 

 that career over the desolate plains of the north. Wherever 

 we turn, we every where see the same mantle of green spread 

 over the earth ; and, even in the most distant lands, our eyes 

 are cheered by that enlivening verdure which adds such a 

 nameless charm to every rural scene. The same wild pro- 

 fusion reigns, and nature teems with never-failing abundance. 



** Thus spring the living herbs, profusely wild, 

 O'er all the deep-green earth ; 

 With such a liberal hand has Nature flung 

 Their seeds abroad." Thomson, 



But was the scene always so fair ? was there always the 

 same display of vegetable riches ? or was there a time when 

 the earth was a desolate and barren wilderness, a mass of 

 craggy precipices, rocks piled on rocks, without any trace of 

 organic life? 



" Where eldest Night, 



And Chaos, ancestors of Nature, held 



Eternal anarchy, amidst the noise 



Of endless waves, and by confusion stood.'* 



This, doubtless, was the state of our globe, for ages before 

 the earth was sufficiently modified to admit of the existence 

 of vegetables. With their original creation we have not at 

 present to do : it is our object, in this paper, to discuss the 



