278 WILD FLOWEBS OF 



thus a distinguishing feature given to characterize the 

 floras of particular parts of the earth from the earliest 

 times. If we admit with geologists a " Grlacial 

 Period," when only the summits of our present 

 mountains were elevated above the waters, and the 

 plants now upon these mountain summits then grew 

 upon the shores of a widely extended ocean, it can 

 have been only by degrees and in a long period of time 

 that other plants have appeared by successive immi- 

 grations to clothe the hills and plains as they became 

 fitted for vegetable growth. Hence some plants may 

 have appeared at a much later period than others, 

 even though disseminated by Nature. On this point 

 I shall not, at present, dwell farther, but it is certainly 

 interesting to the practical botanist to mark those 

 plants that seem cosmopolites winging in every direc- 

 tion, while others, from peculiarity of structure or 

 habit, seem fixed to that locality where the first beam 

 of light dawned on their opening foliage. 



The epiphytical plants of an old tower or ruin are 

 frequently curious, and they serve to invest the moul- 

 dering arches with an adornment that renders them 

 doubly interesting to the view of the artist, the poet, 

 and even the botanist. For, besides the beauteous 

 ivied tracery that almost invariably robes the broken 

 wall, the ash saplings and wild roses that are sure to 

 dangle there, and the wallflowers that perfume even 

 the damp dungeon now exposed to the inlet of day, I 

 have often met with wandering plants that gave a 

 peculiar feature to the pile where they had taken up 

 their abode. I remember Buildwas Abbey bright 

 with the yellow flowers of the Barberry ; the majestic 

 turrets of Pembroke are overgrown with the silver 



