The Life History of Polythrincium Trifolii Kunze. 219 



has never previously been recognised. It is true that Cooke (6) 

 describes such a stage with "Ascis clavatis. Sporidiis elHpticis, 

 continuis, hyaHnis, •oi--oi2 x -005 mm. From specimen in 

 Herb. Berkeley," but an examination of the specimens in the 

 Kew Herbarium has not revealed such a stage. It is possible 

 that he was dealing with a fungus other than the one under 

 discussion. Clevenger(5) recorded mature asci and ascospores 

 in specimens he named Phyllachora Trifolii (Pers.) Fuck, on 

 Trifoliiim worniskioldii. Theissen and Sydow(i4) regard these 

 specimens as a new species which they call Phyllachora umhilicata. 

 (Incidentally it may be remarked that these authors state that 

 they have examined specimens of P. Trifolii from many places 

 but have never found asci ; the European specimens distributed 

 under this name, however, are identical with the type specimen 

 of Sphaeria Trifolii Pers. which the}^ have examined.) 



I. Conidial Stage. Leaves of TrifoliiDn rcpcns affected by 

 Polythrincium Trifolii were found at Tanworth-in-Arden, at 

 the end of October, 1920. The fungus attacks the under surface 

 of the leaves, producing olive-brown to black cindery patches, 

 consisting of punctiform stromata crowded together, which 

 gradually coalesce to form the characteristic relatively large 

 stromata (i ■; -5 mm. or less). During this stage of the life of 

 the fungus the leaves remain green, but fade later. There is no 

 colour zonation round the black stromata, indicating progressive 

 destructive action of the fungus such as is seen when Pseudo- 

 peziza Trifolii grows on the same host. The yellow tissue sur- 

 rounding the black spots to which Kunze (2) refers has not been 

 seen. The leaflets of the infected leaves take an upright position 

 and are thus easily distinguished from healthy leaflets which 

 are extended horizontally. It is, of course, not uncommon for 

 leaves attacked to assume an abnormal position, the phenomenon 

 being perhaps best seen in the rusts. Finally the whole clover 

 leaf withers and when it has fallen to the ground soon decays. 

 The fungus is apparently attractive as food to certain insects, 

 as leaves are frequently found spotted with holes, marking the 

 position of eaten stromata. 



In surface view^ under low magnification, the stromata appear 

 to be powdery, owing to numerous spores on the crowded conidio- 

 phores, which have burst through the cuticle of the leaf (fig. i). 

 Stromata, which are easih' found in different stages of develop- 

 ment, arise in two different ways; either by infection from a 

 conidiospore, pycnospore or ascospore, or by infection from 

 hyphal branches, arising in a stroma already present. In both 

 cases the first signs of infection are very similar ; a few^ fuscous 

 hyphae, often developing beneath a stoma, form a plate-like 

 mass of parenchymatous cells and from these the conidiophores 



