122 BRITISH GALLS, 



Economic Notes 



Many gall-causing fungi are dreaded pests. The " black 

 scab " of Potatoes and Beet is caused by Oedomyces leproides 

 Trb. Large nodulose fleshy tumours occur on the upper 

 part of the root of the Beet and on the young tubers of the 

 potato. 



Chrysopkyctis endobiotica Sch. causes gall-like growths on the 

 tubers and lower leaves of the Potato (see Journal of Board 

 of Agriculture, ix., igo2, p. 320, paper by Professor Potter). 



Exoascus deformans attacks the leaves of Nectarine, Peach, 

 and Almond. The leaves become greatly hypertrophied 

 and distorted, and brightly tinted with red and purple. This 

 disease is very common. Puccinia fahae causes thickened 

 white spots on the seed-pods of Beans and Peas. 



The parasitic Rose canker Comothyrium Fuchelii attacks 

 cultivated as well as wild Roses, causing cankered over- 

 growths on the stems. It apparently attacks Rubi also. 

 Plate XXVI. depicts cankered stems of Rubtts plicatus from 

 Dungeness. 



An excellent illustration of a BuUace branch bearing what 

 are popularly known as " pocket plums " or "bladder 

 plums" may be seen in Plate XXV. This swollen and 

 deformed condition of the fruit is caused by Exoascus pruni, 

 a fungus which also attacks the Sloe, Wild Cherry, and 

 cultivated Plums. The fruit of the fungus appears as a 

 delicate whitish bloom in July. The fungus does not spread 

 backwards on a branch, and may be kept in check by hard 

 pruning. 



The researches of F. P. Brzezinski on " Canker," extend- 

 ing over a period of seven years, indicate that the fungus 

 Nectria ditissima, previously thought to be the cause of this 

 disease, is only a saprophyte growing on dead tissue 

 destroyed by other agents (see Comp. Rend., May 20, 1902). 

 Probably, as remarked above, the canker is in most cases 

 due to the presence of insects or of a bacterium. 



