62 HORTICULTURIST'S RULE-BOOK. 



potash in the soil. Other uncongenial conditions of soil 

 and climate may aggravate it. 



RIPE-ROT (Glwosporium fructigenum, Berk.). See under 

 APPLE. The treatment for black-rot is efficacious for this. 



Hollyhock. RUST (Puccinia Malvacearum, Mont.). Ap- 

 pears upon leaves of hollyhocks and a few related plants 

 in small, light brown patches. Introduced from Europe, 

 and becoming common in this country. 



Remedies. To destroy the plants is the only general 

 method yet employed to prevent the spread of the disease, 

 but spraying early with Bordeaux mixture is to be advised. 



Lettuce. MILDEW (Peronospora gangliformis, De Bary). 

 A delicate mildew, attacking lettuce-leaves and causing 

 yellow or brown spots, and finally killing the leaf. 



Preventives. (According to Maynard.) Grow at a low 

 temperature (35 to 40 at night, 50 to 70 during day) ; 

 give abundance of plant-food; give abundance of water, 

 but apply it in morning and bright days only ; avoid sudden 

 extreme changes of temperature. 

 Remedy. Fumes of sulphur. 



ROT (Botrytis vulgaris, Fries.) . Forced lettuce often rots 

 down, particularly the heading varieties. The fungus 

 which causes the rot lives in manure and decaying matter. 

 If manure is used, mix it well with the soil, keep the soil 

 stirred on top and avoid keeping it too wet. Spreads most 

 rapidly in a moist, confined atmosphere. 



Maple. LEAF-SPOT (Phyllosticta acericola, C. & E. ). Attacks 

 the leaves of red, silver, and striped maples in spring, caus- 

 ing them to become spotted and unsightly, and lessening 

 the vigor of the tree. 



Remedies. Rake and burn the leaves in autumn. When 

 the leaves are two-thirds grown spray with Bordeaux mix- 

 ture, and repeat every three or four weeks as long as 

 necessary. 



Moss or Lichens on trees is readily removed by spraying with 

 Bordeaux mixture, or strong alkaline washes. (See Chap. 

 VI.) 



