236 DISEASES OF CULTIVATED PLANTS 



allied to R. radiciperda (Massee) and R. necatrix (Prill), and 

 spreading in a similar manner by means of subterranean 

 mycelium and conidial fruit. The following note accom- 

 panied the specimens,, sent to Kew from the Botanic Gardens, 

 Singapore, by H. Ridley, F.R.S. : 'Some months ago all the 

 shrubs in a jungly bit of the garden, at the foot of a large 

 Ficus dubia, began to die, turning black, and the long roots 

 of the Ficus did the same. At first I thought some weed- 

 killer had been carelessly thrown into the wood, but the 

 thing increased, every plant withered and died, looking as if 

 acid or boiling water had been thrown upon it. All kinds 

 of Dicotyledonous shrubs and herbs, rattans, Dracaenas, and 

 even some Diffenbachias turned black and rotted. At last 

 the thing developed on the fig roots and on the collar and 

 roots of all the trees and shrubs around, and appears to be 

 a deadly fungus.' 



Perithecia densely crowded, black, echinate ; asci cylin- 

 drical, 8-spored ; paraphyses filiform ; spores fusiformly 

 navacular, ends very acute, opaque brown, glabrous, 

 90-100 X 12 /A. 



Massee, Kew Bulletin, 1901, p. 155. 



Rhizoctonia violacea (Tul.) is the provisional name 

 given by Tulasne to sterile fungus mycelium, which attacks 

 and kills numerous different kinds of plants belonging to 

 widely separated natural Orders. It is well known in con- 

 nection with saffron, the bulbs of which are destroyed in a 

 wholesale manner. The roots of carrot, beetroot, asparagus, 

 lucerne, etc., are destroyed ; the tubers of potatoes, and 

 many bulbs are also attacked. The mycelium behaves in a 

 slightly different manner, and presents a modified appearance 

 when growing on different hosts, hence several different 

 species of Rhizoctonia (all sterile) have been proposed, but 

 infection experiments have proved the soundness of Tulasne's 

 conclusion that all belonged to one and the same species. The 

 infect bulb or root becomes covered with a rather loose weft 

 of reddish-violet or brownish mycelium, which begins as a 

 scattered, loose network creeping over the surface of the part 

 attacked, and gradually becomes more compact and spread- 

 ing, until the entire root or bulb is coated with the mycelium. 

 The hyphae forming the superficial weft of mycelium are 

 usually straight, 4-6 //, thick, septate, and generally give off 

 branches at right angles to the parent hypha. When the 



