260 VEGETABLE FOES AND DISEASES 



yard manure, as this particular scab is most prevalent 

 where the land has been heavily manured. Use a 

 dressing of lime and any approved artificial fertiliser 

 in preference to stable or farmyard manure. The 

 seed must be free from oospore spores, or be treated 

 with the following as advised by Professor Bolley : 

 Immerse the Potatoes, after placing in a sack of 

 open texture, for an hour and a half in a solution 

 consisting of two and a quarter ounces ot corrosive 

 sublimate to fifteen gallons of water, after which they 

 may be cut and planted as usual after being spread 

 out to dry. The corrosive sublimate should first be 

 dissolved in a few gallons of hot water, placing the 

 solution in a wooden vessel, as the mixture corrodes 

 metal. The solution is a strong poison, but does 

 not work injury unless taken into the stomach. 

 Great care should be taken in handling the pure 

 substance and all treated Potatoes must be planted. 



THE ILLUSTRATIONS SHOW POTATO SCAB. 



A, Ashleaf Kidney Potato affected by ordinary scab fungus (Soro- 

 porium scabies) : a, small scabs called sori or seats of fungus 

 growth ; b 9 large scab in rough patches, often due to mechani- 

 cal agency and not always caused by parasites. B, sorus (or 

 scab on Potato skin) of Sorosporium scabies in early stage. 

 x 3. C, spores of Potato scab fungus (Sorosporium scabies). 

 x 300. D, Periola tomentosa, a fungus found on scabbed 

 Potatoes in stores, x 300. E, Potato affected by American 

 Potato scab (Oospora scabies) : c, swellings caused by fungus ; 

 d, scabs. F, early stage of Oospora scabies sorus. x 3. G, 

 aerial hyphae and conidia of Oospora scabies, x 300. H, spores 

 of Oospora scabies, x 300. 



