A VI E W 



OF THE 



STRUCTURE AND GENERAL HISTORY OF LICHENES. 



LICHENES are Plants: of all plants most frequent throughout the 

 globe ; appearing wherever are rocks, stones, earth, and living or 

 dead wood ; wherever there is air moving over earth, and light, 

 and time is given ; extending from the burning deserts of the torrid 

 zone to the frozen deserts of the arctic zone ; ascending to the 

 highest naked rocks of the highest alps ; ceasing only at perpetual 

 water and perpetual snow. 



Lichenes are (considered as belonging to the system) an order of 

 Algse, or Protophyta, which is a section of Thallophyta. 



THALLOPHYTA (Homonemese, Fr.) are the lowest forms of vege- 

 table life. With one of the two sections into which this greater 

 division falls, Protophyta or Alga?, vegetation has been said to 

 begin and from it to ascend : with the other, Hysterophyta, or Fun- 

 gi, the whole vegetable system to be, as it were, concluded and 

 finished. 



Thallophyta are plants merely cellular ; the external organs of 

 which are confused and coadunate in one body ; with a system of 

 fructification immediately originating, by simple metamorphosis, 

 from the primary vegetative system, the cells collapsing into spo- 

 ridia, and these germinating, themselves being prolonged into 

 threads, which are either discrete, or confluent in a homogeneous 

 mass. 



PROTOPHYTA, or Algae, are Thallophytal plants, and are either 

 aerial or aquatic ; they are distinguished by having reproductive 

 gemmaceous cells (gonidia), which are the prototype or elementary 

 analogue of leaves; they are successively developed and indefinite; 

 and absorb nutrition from the surrounding element. 



HYSTEROPHYTA, or Fungi, are Thallophytal plants, which are 

 produced in decaying or perished organic matter ; which want go- 

 nidia ; and are thence at once perfectly developed without succes- 

 sive evolution, and definite ; and absorb nutrition only from the 

 matrix. 



Ols. In Algffi, we discern the progressive series of Thallophy- 

 ta; wherein the vegetative system is especially developed, and 

 affinity both with superior and inferior sections is indicated ; in 

 Fungi, the regressive series is evidently expressed. The whole 

 Fungus is a fructification, and in this the Fungi as much excel, as 



