THE PAGE OF NATURE. 67 



which the slightest touch of the tiniest insect's wing 

 can dislodge, and send away on the breeze in search of 

 a habitat for another colony. 



Most of the crustaceous lichens are merely grey filmy 

 patches inseparable from their growing places, indefinitely 

 spreading, or bounded by a narrow line-like border, which 

 always intervenes to separate them when two species 

 closely approximate, and studded all over with black, 

 brown, or red tubercles. The foliaceous species, again, 

 are usually round rosettes of various colours, attached by 

 dense black fibres all over their under-surface, or by a 

 single knot-like root in the centre. Some are dry and 

 membranaceous ; while others are gelatinous and pulpy, 

 like aerial sea- weeds left exposed on inland rocks by the 

 retiring waves of an extinct ocean. Some are lobed with 

 woolly veins underneath ; and others reticulated above, 

 and furnished with little cavities or holes on the under- 

 surface. The higher orders of lichens, though destitute 

 of anything resembling vascular tissue, exhibit consider- 

 able complexity of structure. Some are shrubby, and 

 tufted, with stem and branches, like miniature trees; 

 others bear a strong resemblance to the corallines of our 

 sea-shores ; while a third class, " the green-fringed cup- 

 moss with the scarlet tip," as Crabbe calls it, is exceed- 

 ingly graceful, growing in clusters beside the black peat- 

 moss or under the heather tuft, 



"And, Hebe-like, upholding 

 Its cups with dewy offerings to the sun." 



As an illustration of the extraordinary appearances 

 which lichens occasionally present, I may describe the 

 Opegrapha or written lichen (Fig. 7), perhaps the most 



