H. olivaceum [Corda] Bcni. — A New British Record. i8; 



HORMODENDRON OLIVACEUM (CORDA) 

 BON -A NEW BRITISH RECORD. 



By F. C. Ford Robertson, B.Sc, 

 Probationer, Indian Forest Service. 



(With one text figure.) 



The source of the material was some mummy plums infected 

 with Sclerotinia sp. collected at Faversham, Kent, in April 1922 

 by Dr Malcolm Wilson. In the course of making cultures to 

 obtain the Sclerotinia an ohve-green mycehum was found which 

 bore no resemblance to that of the latter fungus. Pure cultures 

 were obtained from it by spore isolation and the formation of 

 h^'phae and conidia studied in a hanging drop of glucose solution. 

 Germination takes place readily, the germ-tube, at iirst hyaline, 

 becoming septate and ohve- 

 green in about thirty hours 

 and sending out branches in 

 all directions. Conidiophores 

 are soon developed in profusion. 

 They are erect, of the same 

 ohve-green colour, and are den- 

 dritically branched, three or 

 more branches arising from the 

 same point: on these branches, 

 by abstriction, the conidia are 

 formed, in a somewhat irregular 

 catenulate manner; they are 



unicellular, globose to ovoid, ohve-green to fuscous, 4-6-'/ -^ \ 3- 

 5-5 /x and are joined to one another by a shght h3^ahne neck 

 (see a in the figure). There is a tendency for the conidiophore 

 branch, when forming conidia, to break up into short lengths of 

 hyphae with two or three septa, and these latter break up to 

 form the more elongated conidia (see b in the figure) . 



The fungus has been identified as Hormodcndron olivaceum 

 (Corda) Bon., one of the Dematiaceae. It differs from other 

 species of Hormodcndron in the mode of production of the coni- 

 diophores and in the size and shape of the conidia. The species 

 most resembhng it are H. Hordei Bruhne and if. chlorinum var. 

 nigrovirens (Fresen.) Sacc, but the former is characterised by 

 warted conidia, while in the latter there is no hyahne neck uniting 

 the conidia into chains. It differs from H. cladosporioides (Fresen.) 

 Sacc. in its almost globose conidia. 



H. olivaceum has not been pre\'iously recorded in Britain but 

 has been found on the continent growing on birch wood. 



