132 FOOTNOTES FROM 



as hard as the rock upon which it is produced, over 

 which the devastating storms of the Alpine summit sweep 

 for years without inflicting upon it the slightest injury. 



The colour of the Lemania, when fresh, is of a fine 

 deep olive-green ; but it changes to black when dried 

 and placed in the herbarium. The dilatations or gouty 

 joints, are owing to the development of the sporules 

 within the fronds ; and these may be squeezed out by 

 being compressed between the fingers. The force with 

 which they naturally break through the tough and car- 

 tilaginous skin of the frond, in order to form independent 

 individuals, is not the least curious circumstance in the 

 economy of this strange plant. Bory, to whom we are 

 indebted for the name, informs us that the recent fila- 

 ments of the Lemania, owing to some unascertained gas 

 shut up in the knots, when applied to the flame of a candle 

 explode and extinguish it, while a remarkable movement 

 of retraction is felt by the fingers which hold them. 



The confervas generally grow in single branchless 

 filaments, forming a loose fleecy stratum ; but sometimes 

 they are aggregated together into singular forms. There 

 is one species known as the water-net or water flannel, 

 (Hydrodiciyon utriculatum), which looks more like a piece 

 of green baize manufactured by man, than a production 

 of nature. It forms a beautiful tubular purse or net, 

 with regular polygonal meshes, varying from half a line 

 to half an inch in diameter, grey on the one side, and 

 green on the other. The filaments which compose these 

 meshes are sometimes slender as a horse hair, and some- 

 times as coarse as a hog's bristle, feeling harsh to the 

 touch when handled. There is no granular fructification 



