66 INTRODUCTION TO C'RYPrOGAMIC BOTANY. 



like chemical substances from inorganic matter, according to 

 definite laws, the species would, in all probability, admit of far 

 more accurate definition : at any rate the species of Cryptogams 

 in general are not more certain than those of Phaenogams. 

 Some, however, maintain, on the contrary, that there can be 

 no certain species of Cryptogams on this account. There are, 

 however, in no part of Botany more certain species than those 

 of the higher Hymenomyceies when properly understood, 

 especially, as Fries remarks, in the genus Cortinarius. 



63. Cryptogams, then, as a distinct class of organised beings, 

 and from various considerations connected with them, form a 

 very important object of investigation. They are, for the most 

 part, the first objects which clothe naked rocks when they emerge 

 from the bosom of the sea, and they afford the last indication of 

 vegetable forms under degrees of heat and cold which are fatal 

 to other members of the same kingdom. Stones of the closest 

 texture, if there is a proper degree of moisture, even under 

 the direct 'rays of the sun, soon exhibit traces of Cryptogams, 

 and in hot springs, at temperatures which seem almost fabu- 

 lous, certam species will flourish ; while the depths of the 

 Arctic and Antarctic Seas and the brashy pancake ice are 

 equally productive. There is, moreover, a singular variety in 

 the nature of these bodies, so that there is scarce a part of the 

 surface of the globe where they may not be found. Both fresh 

 and salt water, within certain limits as to depth, and tempe- 

 rature, teem with them ; arid plains, turfy peat-mosses, the 

 recesses of woods, the deepest mines, the surface even of 

 icebergs, and, if it be not a mere fancy of Ehrenberg's, the 

 bowels of the earth and the regions of air are not exempt; 

 and then not only are there multitudes of forms amongst 

 them of excessive minuteness, but some of the noblest objects 

 in nature, as the tree ferns, belong to the same class. They 

 are often the pests of man, spoiling his provisions, and inter- 

 fering with the operations of art. Neither are living organisms 

 exempt. True parasitism exists in Cryptogams, which, in con- 

 sequence, give rise to a host of diseases, especially in the farm 

 and garden, and wherever vitality is very low, certain species 

 are capable of establishing themselves on exposed surfaces 



