Tobler gives the results of his examination of still another fungus, _Karschia destructans_. It becomes established on the thallus of _Chaenotheca chrysocephala_ and its hyphae gradually penetrate down to the underlying bark (larch). The lichen thallus beneath the fungus is killed, but gonidia in the vicinity are sometimes clasped: _Karschia_ also is thus a parasymbiont, then a parasite, and finally a saprophyte. Elenkin[954] describes certain fungi which to some extent are parasymbionts. One of these, _Conidella urceolata_ n. sp., grew on forms of _Lecanora esculenta_. The other, a stroma-forming species, had invaded the thallus of _Parmelia molliuscula_, where it caused gall-formation. As the growth of the gall was due to the co-operation of the lichen gonidia, the fungus must at first have been a parasymbiont. Only dead gonidia were present in the stroma; probably they had been digested by the parasite. Because of the stroma Elenkin placed the fungus in a new genus, _Trematosphaeriopsis_. _e._ FUNGI PARASITIC ON LICHENS. A solution or extract of lichen thallus is a very advantageous medium in which to grow fungi. It is therefore not surprising that lichens are a favourite habitat for parasitic fungi. Stahl[955] has noted that the lichens themselves flourish best where there is frequent moistening by rain or dew with equally frequent drying which effectively prevents the growth of fungi. Species of _Peltigera_ are however able to live in damp conditions: without being injured, they have been observed to maintain their vigour when cultivated in a very moist hothouse while all the other forms experimented with were attacked and finally destroyed by various fungi. Lindsay[956] devoted a great deal of attention to the microscopic study of the minute fruiting bodies so frequently present on lichen thalli and published descriptions of microlichens, microfungi and spermogonia. He and others naturally considered these parasitic organisms to be in many cases either the spermogonia or pycnidia of the lichen itself. It is often not easy to determine their relationship or their exact systematic position; many of them are still doubtful forms.