ROSELLINIA 235 



Various other kinds of trees are also injured by this parasite. 

 The mycelium at first forms thin white patches on the bark 

 of the root ; these patches gradually extend over the surface 

 of the root and form crust-like stromata, black externally, 

 whitish inside. At this period the mycelium forms strands, 

 and changes in colour to a dark brown. The mycelium 

 penetrates every portion of the root, being most abundant in 

 the medullary rays. When the black crust-like patches or 

 stromata are fully formed, the vegetative activity of the 

 parasite is arrested, and the production of productive bodies 

 begins. 



During a continued period of dampness, the surface of the 

 black stromata becomes covered with a delicately velvety, 

 olive growth consisting of densely packed conidiophores. 

 As development proceeds the velvety pile changes to a 

 grey colour, due to the growth of hyaline branched tips to 

 the conidiophores. These hyaline tips are irregularly 

 branched, each branchlet bearing several elliptical, almost 

 hyaline conidia, 7-10x6-7 p. This conidial form of the 

 Rosellinia is the Trichosporium fuscurn, Sacc. ( = Sporotrichum 

 fuscuni). At a later date, when the host is quite dead, often 

 only after it has been dead for some years, the crowded 

 black perithecia of the ascigerous fruit appears on the black 

 velvety patches that had previously borne the conidial form 

 of fruit. 



Ascigerous form. Perithecia crowded, black, shining, 

 large; asci cylindric-clavate, 8-spored, 150-170 /* long; 

 paraphyses cylindrical, slender, longer than the asci; 

 spores elliptical, brown. 



The collar and superficial roots are the parts attacked, 

 and the tree is usually killed within four or five years. A 

 damp situation favours the disease. 



Prillieux, Malad. des Plantes Agric., 2, p. 125 (1897). 



Rosellinia ligniaria (Nitschke) has been noted by Mr. 

 W. Carruthers, F.R.S., to attack living ash-trees, eventually 

 killing them. Specimens were exhibited at the Linnean 

 Society's Meeting, Dec. 16, 1897. 



Perithecia gregarious, conico-globose, superficial, black, 

 sparingly covered with minute hairs, |- mm. diam. ; asci 

 cylindrical, 8-spored ; spores blackish-brown, continuous, 

 1 6 x 8 p. 



Rosellinia echinata (Massee), a very destructive parasite, 



