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On the Dual-Lichen Hypothesis. 



By M. C. Cooke, M.A., LL.D., &c. 



CRead March 28th, 1879. ) 



[Abstract.]* 



" That hypothesis which is based on sound scientific knowledge is sure 

 to have a corresponding value, and that which is a mere hasty random 

 guess is likely to have but little value."— Prof. Huxley Lectures (1863 j, 

 p. 67. 



Truth has often been discovered by the aid of a hypothesis, hence 

 the proposition of a hypothesis for the advancement of science is 

 perfectly legitimate. Some hypotheses which have been proposed in 

 the past have proved utterly untenable when they have been 

 assailed ; therefore, before any hypothesis is accepted, it should be 

 subjected to all possible tests. Any hypothesis which cannot suffer 

 criticism is not worthy of acceptation. The dual-lichen hypothesis 

 is worth very little if unable to meet all the objections which such an 

 assailant as the present can urge against it. 



Without contenting myself with reviewing the remarks of single 

 individuals, I will rather go direct to the main source of the theory 

 of which Schwendener is the author. In a few brief sentences the 

 whole gist of the hypothesis may be summarized. Although at first 

 only the group called the Collemacece were included, ultimately, as 

 his views extended, he included all Lichens in the category of Algo- 

 fungi. These are his words, " As the result of my researches, all 

 these growths (Lichens) are not simple plants, not individuals in 

 the ordinary sense of the word ; they are rather colonies, which con- 

 sist of hundreds and thousands of individuals, of which, however, 

 one alone plays the master, while the rest in perpetual captivity 

 prepare the nutriment for themselves and their master. This master 

 is a fungus of the class Ascomycetes, a parasite which is accustomed 

 to live upon other's work. Its slaves are green alga3, which it has 



* The full text of this paper will be found in " Grevillea " for March and 

 June, 1879.— Ed. " Q.M.J." 



