RECENT OBSERVATIONS ON THE GONIDIA QUESTION. 133 



further saturated with a httlc of the solution of the ash of the 

 different lichens. 



All these " cultures in the mass" took place in a moist atmo- 

 sphere. Yerj soon I used instead of freely ffroivinff Cystococcus 

 for my cultures, that which I had previously set free from the 

 lichen thallus (see below). The Cystococcus was always 

 furnished by another lichen than that wherefrom the spores 

 were taken ; for example, spores of Xanthoria were sown 

 upon a substratum with Cystococcus from Ramalina, in order 

 that the presumption should never occur, in case of eventual 

 success of the culture, that the thallus was caused by the 

 continuous growling of portions of the hypha set free whilst 

 still attached upon some Cystococcus-exa.mY>les, as, indeed, 

 thin sections of some homoiomerous lichens may, under 

 favorable circumstances, grow on afresh to become a perfect 

 thallus. 



The greater part of these experiments were carried on in 

 the way made known by Reess as necessary to cause 

 homoiomerous lichens to originate ; the spores were first 

 sown, and about ten days after the algse. When this mode, 

 however, did not afford me the least result, I then, between 

 15th October and 1st December, 1872, made further culture 

 for the fifteenth time, in which spores and algse were sown 

 simultaneously in order to see if the mode of culture requisite 

 for the homoiomerous lichens had acted possibly injuriously 

 for heteromerous lichens, and was the cause of the failure of 

 the experiment. 



In this summer I have not repeated the cultures ^'in the 

 mass " in a moist atmosphere ; however, I have tried to 

 obtain Xanthoria parietina by sowing its sjDores with Cysto- 

 coccus hmnicola in the open air upon tiles and bark of trees, 

 lasting from 8th July to 3rd October. 



All my cultures *'in the mass" of the preceding year had, 

 in no case, the least result. After a month and a half (taken 

 as the mean of those cultures), with the naked eye there was 

 no trace of thallus-formation perceptible, but even a micro- 

 scopic examination presented nothing resembling lichen- 

 formation. This non-success was almost always the result 

 of formation of mould. 



In my cultures in the open air during this summer I 

 found, more than once, on the very limited spots of the bark 

 on which I had sown spores and algae, after about three 

 weeks' culture, very distinct commencing thallus-formation; 

 I was never able, however, with minute microscopic examina- 

 tion, to find the connexion between such a young thallus and 

 a germinated Xanthoria spore ; this appeared almost to be 



