102 Transactions British Mycological Society. 



reality dealing with a mixture of the two fungi, and shows that 

 the results cited above are compatible with this hypothesis. For 

 example, Laurent states that on one occasion he found conidio- 

 phores of Cladosporiiim arising from mycelium of Dematium 

 in cultures of pollen grains in sugar solution, "avec lesquelles 

 il n'etait pas possible d'eviter I'envahissement par le Dematium 

 des chambres humides placees sous le microscope." The De- 

 matium arose as a laboratory contamination ; is it not conceivable 

 that Cladosporium should originate from a similar cause? The 

 apparent development of one form into the other would doubt- 

 less be enhanced by the striking similarity between the two 

 mycelia, to which reference has already been made. These and 

 other facts recorded by Planchon cast grave doubts upon the 

 purity of the cultures. 



As to the development of Dematium mycelium in the beer- 

 wort tube cultures of Cladosporium spores, similar experiments 

 repeated by Janczewski and by Planchon gave negative results. 

 Here again Planchon invokes the hypothesis of a mixed culture ; 

 he suggests that Cladosporium loses its vitality relatively rapidly 

 and supposes that this fungus perished during the prolonged 

 exposure to sunlight so that the more resistant Dematium 

 developed alone. 



The more delicate task is to offer an explanation of Laurent's 

 figure of a Cladosporium conidiophore in organic connection 

 with a hypha of Dematium ; this Planchon achieves by asserting 

 the occurrence of growths of Cladosporium in which the conidia 

 assumed an abnormal arrangement resembling Dematium 

 pullulans. That is to say, the figure is believed to be based on 

 a misinterpretation of the observed facts. 



Finally Planchon argues that if Dematium be a weakened 

 form of Cladosporium, cultivation of either type on similar 

 media should be expected to lead in time to a convergence in 

 the growth forms, which is contrary to fact. 



In short, Laurent's evidence alone is not considered sufficiently 

 satisfactory to warrant the assumption of a genetic relationship 

 between the two fungi in question. It now remains to examine 

 any further evidence brought forward in this connection. 



Massee ( 7) ascribes a gummosis of Prunus japonica to an un- 

 determined species of Cladosporium, and states that the disease 

 was reproduced by inoculation of wounds with the spores of 

 this fungus. The gummy masses exuding from the bark were 

 found to contain hyaline hyphae and also chains of irregular 

 dark cells, the latter on germination producing budding spores. 

 In hanging drops and in flask cultures these brown cells gave 

 rise to a stout, hyaline mycelium abstricting budding spores, 

 and identified as Dematium pullulans. Finally, the author 



