316 THE JOUBNAL OF BOTANY 



acute at one or both ends, sometimes bent at the septum, 10|-12 x 

 3-3| /i, cells often unequal. 



On diy dead stems of Eqiiisetum limosmn. Ardi'ossan (Boyd). 

 Harborne ; King's Norton. Mar.-Apr. The so-called Phoma, which 

 has been recorded as British by Bucknall and by Broome, is merely 

 the young undeveloped state; both kinds of spores may be found in 

 the same pycnidium. 



278. AscocHTTA Mercueialis Grove. 



? Phyllosticta mercurialls Desm. Sacc. Syll. iii. 53. 



Spots large, indefinite, greyish-ochreous, without a distinct border. 

 Pycnidia epiphyllous (usually), ± crowded, immersed, lens-shaped, 

 pale brownish-yellow, 100-125 /u diam., pierced at length by a delicate 

 poi-e ; tissue soft, plectenchymatous, firmer round the pore. Spores 

 oblong, rounded above or at both ends, usually straight, rarely guttu- 

 late-septate, 9-10 x 2^-3 ^. 



On living leaves of Mercurialis perennis. AiTan and Ayrshire 

 (Boyd). July, Aug. 



The species originally described by Desmazieres is very doubtful, 

 some mistake having apparently crept in : it is suggested that it is a 

 misunderstood Cercospora, which seems improbable with so careful 

 an observer. But the specimens which are found in herbaria under 

 tliis name appear for a long time as a PhyUosticta, although ulti- 

 mately, as shown by Mr. Boyd's specimens, they develop into an 

 Ascochyta. The spots are more common than the pycnidia ; they 

 are usually described as " small, sometimes confluent," but in the 

 Arran specimens they occupy at least half of the leaf, and are quite dif- 

 ferent in character from those typical of Cercospora Mercurialis Pass. 



279. Ascochyta TiLiiE Kab, & Bub. in Hedwig. xlvi. 293. 

 Spots equally visible on both sides, roundish or irregular, variable, 



5-15 mm. diam., of a dark smoky colour, at length becoming thin 

 and translucent-grey, without a border or darker at the margin. 

 Pycnidia generally epiphyllous, numerov;s, densely scattered over the 

 spots, immersed, roundish, 100-150 /u diam., transparent-brownish, 

 with a darker border ; texture as in a true Ascochyta. Spores oblong, 

 rounded at each end or somewhat tapering below, hardly or not at 

 all constricted, hyaline, without guttules or 2-4-guttulate, 8-10 X 

 21-3 /u. 



On living and fading leaves of Tilia grandifoUa. West Kilbride, 

 Ayrshire (Boyd). Jul. 



The spots are usually of a uniform dull colour, without any distinct 

 differently-coloured border, but are nevertheless so definite, and the 

 attacked tissue becomes so disintegrated, that it drops out in frag- 

 ments and leaves a roundish " shot-hole," or a larger irregular one 

 composed of several which are only separated hj the persistent leaf- 

 veins. In no case was there a purple margin, as in some of the 

 Bohemian specimens. 



280. Ascochyta Vibiteni Sacc. Syll. iii. 387. 

 PliyUosticta Vihurni Roum. Fung. Gall. no. 2036. 



Spots irregularly placed, roundish or sinuous, 3-10 mm. across, 

 pallid, Avith a purplish border. Pycnidia epiphyllous, globose-lens- 



