M. C. COOKE ON THE DUAL-LICHEN HYPOTHESIS. 173 



such a plant may be, no one lias raised a doubt as to its being a 

 complete plant. 



Another simple plant, with similar cup-shaped organs, or recep- 

 tacles, enclosing similar reproductive bodies, contained also in 

 cylindrical tubes, but with other organs superadded, such as a 

 foliaceous expansion, analogous to leaf and stem, or it may be some 

 other bodies characteristic of the group to which it belongs ; and at 

 once analogy leads us to the conclusion that this also represents a 

 complete plant. 



If we concede that the Duckweed is a perfect plant, and the 

 Peziza also a perfect plant, then also the Lichen must be a perfect 

 plant. 



Are Lichens (exclusive of their Gonidia] identical ivith Fungi ? 

 The hypothesis in question assumes that the lichen consists of a 

 fungus, enclosing certain foreign bodies, called gonidia. Hence 

 then, lichens, irrespective of the gonidia, should correspond in all 

 respects to the Fungi to which they are referred. The presence of 

 these small organisms may be ignored in our comparison of the 

 supposed fungus with the real fungus of our experience. 



In comparing the general character of Lichens with the general 

 character of Fungi, we may assume that we can arrive at some 

 definite conclusion as to the probability of their identity. We can 

 predicate nothing of fungi except what is confirmed by fact ; and 

 any other organisms, to be affiliated to them, must agree in all main 

 features with the known characters of the Fungi, or they can have 

 no claim to be considered identical. 



It will facilitate this comparison if we are enabled to limit the 

 area, which may be done by accepting the limitation fixed by the 

 Schwendenerian hypothesis that the Ascomycetous Fungi are meant 

 when the term Fungi is used, and as the Sphceriacei have been vir- 

 tually excluded by all advocates of the theory, it may be assumed, 

 as has been admitted, that the Discomycetes are the special group 

 of Fungi to which the Lichens are referred. 



The Discomycetes, in their cup -like forms, are assumed to be 

 identical with the apothecia of certain lichens ; nay, more than this, 

 all Lichens, to whatever genus they may belong, in their totality, 

 excepting only their gonidia, are affirmed to be Discomycetous Fungi. 



" Lichens are perennial ; they grow very slowly, but they attain 

 an extreme age. Some species, growing on the primitive rocks of the 

 highest mountain ranges in the world, are estimated to have attained 



