.'JIG THE JOL'J{XAL OF IJOTAXY 



SEPTORIA CHEXorODII: 



AX Example axd a Warxixg. 



By W. B. Gboye, M.A. 



There is a certain imperfect fungus parasitic on Atrip! ex and 

 Chriwpodiiim to which great interest attaches. The late M. C. Cooke 

 found it at Holloway, in July 186G, forming spots on the leaves of 

 Afriphw, and issued it in his Fungi Britannici as no. 118, under 

 the name Fhi/IIosticta Atriplicis Desm. Though suitable }>laces 

 Avhere its host could grov/ are now much rarer in that thickly in- 

 habited ])art than they were in Cooke's time, a visit to Holloway in 

 August last showed that the fungus still occurred in plenty there, 

 and it was easily found also at Highgate, East Finchley, Wembley, 

 Harrow, Greenford, Brentham, and Hampton Wick, all towards the 

 same side of London. Nevertheless it appears to be somewhat local, 

 for recoi-ds in other parts of Britain are few in number. It seems, 

 furthermore, to be distributed throughout the temperate northern 

 hemisphere, both Euro2)ean and American, and to occur on many 

 species of Atriplex and Chenopodium without much altering its 

 morphological characters. 



13ut an examination of Cooke's specimens shows that, though 

 most of the spores are one-celled (as the}^ should be in Phyllosiicfa)^ 

 yet there are a number which are two-celled, while a long-continued 

 search of specimens from other localities will enable one to discover 

 not a few which are distinctly and plainly triseptate, and even one 

 among about a thousand spores which has five septa. With the one 

 septum, the spores would suggest the genus Ascocltyta ; with the 

 three or five septa, the genera Sepforia or Sfagonospora. But still 

 further, the fungus occurs, though more rarely, on the stems, and in 

 that case bv those who follow the, let us say, to avoid offence, the 

 Chinese method adoi)ted in Uabenhorst's Kriipfogamea-FJoro. by the 

 excellent Allescher, the two-celled form would be placed in the genus 

 Diplutlina. For Allescher's wooden dictum is — Ascocliijta on the 

 leaves, Diplodina on the stems; no other distinction being considei-ed 

 or even suggested. On the stems, it should be noted, the spots 

 occupied by the fungus are not at all wtII marked, but the spores are 

 the same. 



Under these circumstances it is not surprising that the fungus has 

 been found by many different mycologists, and has received many 

 different names. A study of the synonymy will be at once an 

 example of the varying forms which one fungus can assume on its 

 way to full development, and a ^xarning of the necessity of making 

 greater allowance for this variability (on certain fixed lines) than is 

 usually done, before concluding that one has found a new species. It 

 is premised that the spores have a peculiar shape and character which 

 is easily recognisable by the exiK>rt, and that all the variations in the 

 colour of the spots, size of the s])ores, etc., alleged by the different 

 authorities (pioted, can be found in the same localitj^ on the same 

 host, if the investigation be continued long enough. For example, 

 though the width of the sjxjivs is variously given as from 3 to G /x, all 



