M. WESTERGAARD AND H. HIRSCH 



differentiation in Chlamydomonas (see Moewus, 1950). We may take this as a warning 

 against restricting the biochemical part of this work to the melanins only. 



The third implication, ?nd still of course a purely speculative one, might also be 

 mentioned here. Melanins are of widespread occurrence among the higher fungi, both 

 in the Ascomycetes and Basidiomycetes; mushrooms like Psalliota and Lactarius are 

 well-known sources of tyrosinase. The pigments seem always to be associated with 

 reproduction. This brings into the picture the so-called Fungi imperfecti — the fungi 

 which only reproduce asexually, the sexual (perfect) stage being unknown. It would 

 be interesting to compare tyrosinase activity in some of the asexual species with that 

 of related sexual species (e.g. Aspergillus niger with A. nidulans, Penicillium chrysogenum 

 with some of the sexual species) and study the reaction of the asexual species to mela- 

 nin precursors. It would have considerable theoretical as well as practical implica- 

 tions if it should prove possible to induce sexuality in some of the asexual fungi, 

 among which we find some of the most important industrial species. 



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