128 W. ARCHER. 



the process of germination becomes speedily stopped. In all my 

 cultures the mould-formation was then, amongst the obvious 

 difficulties, not only the greatest, but, at the same time, the one 

 against which, notwithstanding all the means applied, nothing 

 could be done. Now, a repetition of my researches in this 

 year at last taught me the circumstances under which the 

 formation of mould is to be obviated, and I carried on cultures 

 for even three months free from this vexatious foe. I saw 

 more spores than formerly of which all the protoplasm was 

 used up in the growth of the germinating filaments, and in 

 which, therefore, germination proper was at an end ; I never 

 saw, however, young gonidia on the germinating filaments in 

 which, by the application of reagents, I satisfied myself com- 

 pletely of the presence of cellulose. If the gonidia originated 

 from the germinating filaments, they should have already 

 made their appearance when the filaments have used up all 

 the reserve nutriment from the spores ; they do not them- 

 selves contain chlorophyll, and thus cannot assimilate and 

 have not the opportunity of taking up organic food for 

 further growth. 



II. Starting on the supposition that Schwendener's theory 

 of the lichens is the true one, the spores about to germinate 

 were brought into contact with nutritive solution for the 

 purpose of trying in this way to cause the germinating fila- 

 ments to grow, after, indeed, the reserve nutriment from the 

 spore was used up. 



It is very probable that both the plan of operations and 

 the purpose of this part of my experiments may be at first 

 glance taken by many as merely haphazard, above all because, 

 so far as I know, no one has ever tried to cultivate a strictly 

 parasitic fungus by nutrient solution only, without the co- 

 operation of the host. This has, indeed, been done for sapro- 

 phytes, and with good results, by sometimes making use of 

 prepared nutrient substances in a fluid state, at other times 

 of decoctions or solutions of the substances whereon the 

 saprophytes grow. Still I think I can quite justify my plan 

 of operation. It is known that most parasitic fungi can live 

 only on one, or, at most, very few hosts, but the conclusion 

 constantly drawn that the hosts are the only plants which 

 contain the nutrient substances necessary for the parasite 

 may scarcely hold good. The phenomenon may have another 

 explanation. Of all the plants which contain the necessary 

 nutritive substances for any parasitic fungus, its host (or 

 hosts) alone fulfils the conditions of containing, at the same 

 time, none of the substances injurious to the parasite. 



Were this mode of explanation of the union of a parasitic 



