Archer — On Apofhecia in Ahjce. 93 



preTiously "well examinecl, which, though if indeed found to represent 

 the alga " pure and simple," would not render it absolutely couciusiya 

 that some other portion of the tuft might not already have been invaded 

 by the "parasite." However, having selected some plants fur experi- 

 ment, they should be well inoculated with spores and portions removed 

 from time to time for examination and experiment. If found satisfactoiy, 

 it would be interesting to tiy to " cross " spores from the same and 

 from different species (as, for instance, such as fig. 5 and fig. 26, or 

 fig. 2 and fig. 19), in order to see the result, and whether the apparent 

 fixity of the forms and the apparently extreme exclusiveness of the 

 "parasites" be true or not, or ultimately whether the theory be true 

 itself or not. Whether, for the time being, the truth of the new theoiy 

 be previously assumed, or its untenability be presupposed, would 

 matter very little, if the suitable opportunity and ready field of opera- 

 tions were at command of the observer. It would seem as if in this 

 way only can either presupposition be justified or negatived. 



Pending the ultimate decision at which the great lichenists who 

 are at work on the broad question may arrive as to the true nature of 

 these interesting plants, and pending, too, the discovery of the sper- 

 mogonia of the forms here referred to, as assisting to throw a light 

 on their mutual affinities and relative position, I may well leave to 

 more skilled hands the desultory notes brought forward in this coui- 

 mumcation, touching their general bearing and ultimate application 

 as regards one of the most interesting and problematic botanical ques- 

 tions of the day. 



R. I. A. PROC, SER. II., VOL. II., SCIEXCE. 



