A Rhizoctonia causing root disease in Uganda. W. Small. 165 



placing it in one of the foim-genera which have been created 

 for the reception of sterile myceha. 



The two form-genera which come into consideration are 

 Rhizoctonia and Sclerotium, both of which as at present con- 

 stituted ob\'iously contain heterogeneous elements and both of 

 which would disappear entireh- with the discovery of the perfect 

 stages of their various species. In deciding the question of a 

 place for the present species, weight has been placed on the 

 structural characters, including the clamp-connections and the 

 probable connection of the species N^th a lower Basidiomycete 

 (in which point it would agree with Rhizoctonia Solani), rather 

 than on the absence of external mycehum, a character which 

 is appropriate to the genus Sclerotium. It is proposed, therefore, 

 to refer the present form to Rhizoctonia and to institute a new 

 species. The specific name, lamellifera, refers directly to the 

 frequent presence and constant character of the sheets of 

 modified hyphae which have been called "sclerotial plates" in 

 this paper, and its use seems the more appropriate inasmuch 

 "as no record of similar structures has been found in the hterature 

 of parasitic species of Rhizoctonia except, perhaps, in the account 

 of Rh. St r obi E. Scholz on Finns Strohus *, a species which was 

 described on a well-grown tree. 

 Rh. lamellifer-\ sp. nov. 



Hyphis Hgnum et corticem profunde penetrantibus, fiU- 

 formibus, crassioribus, ramosis, anastomosantibus, demum fus- 

 cescentibus, septatis, non superhcialibus, interdum in mem- 

 branam castaneam coalitis; membranis e celluhs contextis, 

 irregularibus, angulatis compositis, plerumque in Hgno corticeque 

 immersis, vel rarius externis, subinde corpora basidiis et sterig- 

 matibus simihter gerentibus, Sclerotiis numerosis, fere le\'ibus, 

 globosis vel p}Tiformibus, saepe complanatis, haud erunipentibus, 

 ad I mm. longis, -S mm. latis, e celluhs pseudo-parench\Tnatis, 

 irregularibus, 5-10 /x diam. compositis, Sclerotiis guttulas 

 oleosas copiosissimas includentibus. Hah. in ligno et cortice 

 radicum \iventiimi Grevilleac rohiistae (typus), Theae, Bixae 

 Orellanae, Coffeae rohustae, Casuarinae equisetifoliae cultae quas 

 necat. 



Summary. 



1. A new species of Rhizoctonia has been found to attack 

 Grevillea rohusta, and its morpholog\' and beha\'iour in culture 

 are described. Its distinctive characters are the presence of 

 sclerotial plates and sclerotia. 



2. The connection between the plates and the sclerotia has 

 been established in cultures started from the plates. Owing to 



* Verhandl. zool.-bot. Gesellschaft, Wien, XLVii, p. 541, 1897. 



