329 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



released from an old clubbing, remain in the soil, progress to other and 

 neighbouring roots, and thus continue to perpetuate and diffuse the 

 BpeoieB. Each club root is therefore a centre from which the disease may 

 spread. It is scarcely probable that any of the numerous fungicides 

 will be of any avail to dislodge the parasite when once it has obtained 

 possession. The only feasible remedy is to extirpate by burning every 

 atom of infected roots, and not to plant again on the same spot without 

 removing the whole of the soil, and replacing it by fresh and unpolluted 

 earth. This may seem to be a drastic measure, but with such a foe only 

 measures which are thorough can be effective. 



"Whether a Calif ornian Vine disease, which is attributed to Plasmodio- 

 phora ceUifornica, is the same as the present species, we are unable to 

 determine. 



Gard. Chron. June 17, 1893 ; Mass. PI. Dis. p. 338 ; Mass., Ann.Bot. 

 ix. p. 421, pL ; Tubcuf, Dis. p. 528. 



Another Vine-root parasite was described some years ago under the 

 name of Rosslera hypogcea, which was found on Vine roots after they 

 were really dead, not only in Austria, but in this country. They were 

 little rounded fungi, like the head and upper portion of a large pin, but 

 unfortunately, when they were submitted to that eminent lichenologist, 

 the late Rev. W. Leighton, he pronounced them to be a well-known lichen 

 called Coniocybc pallida. 



Gard. Chron. Dec. 22, 1888, fig. 105 ; Tliiim. Pih. Wcin. p. 210, 

 t. 4, f. 9. 



White Root-rot. 

 Dematophora necatrix (Hartig), PI. XIV. fig. 20. 



This root disease, which affects the Vine as well as other plants, was 

 originally known by the above name, representing the imperfect condition 

 in which it is usually found. 



The mycelium spreads rapidly underground, and when it comes in 

 oontaet with the rootlets of a plant it kills them, and gradually works its 

 way upwards into the larger portions of the root. Sometimes, after 

 travelling upwards, it bursts through the bark at the base of the trunk in 

 B white woolly mass. 



During its progress minute sclerotia are formed, which originate 

 • lark-coloured, rigid, bristly conidiophores bearing numerous conidia at 

 their tips. 



Another kind of fructificatien is sometimes found on decaying roots 

 ui tin form of pycnidia, or conceptacles containing stylospores. 



The highest or ascigerous form of fructification is more rare, and 

 consists of large black peritheoia which include asci and sporidia, and are 

 surrounded by tho bristly conidiophores. In this condition it has been 

 clmracti H e<| under the name of Roscllinia necatrix (Prill. & Del.). 



Spraying is out of the question in such a case, and no cure can be 

 hoped tor when the mycelium is once established. If the disease appears, 

 the affected plants should be isolated by trenching around them. 



Hartig d Somer. Dm. p. 82, with figs.; Viala, Mon. with 5 plates; 

 Mass. PL Dis. p. 118, fig. 21. 



