FUNGOID PESTS OF CULTIVATED PLANTS. Ill 



There is a thin and delicate but profuse mycelium from which arise 

 the fertile branches, which are club-shaped and divided by transverse 

 septa into short joints, which gradually contract at the suture, and then 

 the top joint having acquired an elliptical form falls away as a conidium, 

 to be followed successively by the other joints, so that a continuous crop 

 of mature conidia is ensured. They are externally quite smooth and 

 colourless (28-30 x 12 //). 



The habit and structure of this mould are quite similar to the Oidium 

 of the vine, that which precedes the Rose mildew, and the development 

 of the different species of Erysiphe. 



In 1890 this mould made its appearance on Apple trees in South 

 Africa, and possibly it is the same species as one which is common east 

 of the Mississippi in the United States. 



In such cases dusting with dry sulphur is likely to be the most 

 effectual treatment. In America the application of the ammoniacal 

 solution of carbonate of copper is recommended. 



Grevillea, xvi. 10. 



APPLE-TWIG WHITE MILDEW. 



Sphcerotheca Mali (Duby). 



A century ago one of the fungi closely allied to that of the Rose and 

 the Hop was imperfectly described in France under the name of 

 Erysiphe Mali, but very recently it has been revived by Dr. Magnus, who 

 has seen and figured one of the conceptacles. It was said to be broadly 

 effused ; the thin arachnoid threads of the mycelium interwoven ; the 

 conceptacles rare, and scattered, subglobose, rugulose, and black. 



The mould already described here under the name of Oidium 

 farinosum appears to be the mycelium and conidia of the above fungus, 

 but at present the more perfect and complete condition with the con- 

 ceptacles has not been met with in this country. In this instance we 

 appear to have a " perennial mycelium in the host-plant, which grows along 

 with the shoot each season, stunting its growth and eventually killing 

 the tree." (Fig. 12.) 



Journ. B.H.S. (1902), xxvi. p. 737, fig. 310; Duby, Sot. Gall. 869. 



FRUIT-TREE PUSTULE. 

 Eutypella Prunastri (Pers.). 



This compound Sphceria is only parasitic in the early stage, when 

 spermogonia are evolved in tendrils through punctures of the bark. No 

 one has seen the complete or true Eutypella stage, except on dead tissues. 

 In this condition the perithecia are clustered together in definite pustules, 

 some five or six, with long converging necks, which are sulcate or grooved 

 at the extremity or ostiolum. The fructification is contained within the 

 perithecia, consisting of eight sporidia, enclosed within a transparent 

 ascus, of which there are several. The sporidia are cylindrical, curved, 

 and but slightly coloured (6-8 x 1^ p). 



The spermogonia, which are developed earlier, ooze out in tendrils 

 from the mouths of the receptacles, and are known in this stage under 

 the name of Cytospora rubescens : they are not more than half the length 



