Ornamental Plants 



419 



loss occasioned by the diminution in vigor of the plant and 

 consequent imperfection of bloom is large. 



The sori, 2-3 mm. in diameter, which are diagnostic, first 

 appear as small blisters covered by the epidermis. The 

 rupture of this covering dis- 

 closes a dark brown mass of 

 spores. The sori are usually 

 numerous upon the lower leaf 

 surface, and the spores form 

 dusty coatings upon the 

 leaves. Badly affected leaves 

 curl; shrivel, and die. The 

 plants are dwarfed and fail to 

 produce flowers of value. 



All new stock introduced 

 to the houses should be care- 

 fully inspected and all dis- 

 eased stock destroyed b}^ fire. 

 New stock should be isolated 

 and watched for a month or 

 more to be sure that no 

 rust develops. If disease ap- 

 pears, all affected leaves 

 should be picked and burned 

 with precautions to avoid 

 scattering the spores. If the 

 rust continues to appear, all 

 parts above ground must be 

 destroyed by fire at the end 

 of the season, and plants for 

 the next year raised in un- 

 contaminated soil and house. 



Ray-blight ^^^ (Ascochyta chrysanthemi Stev.). — In this 

 disease, described by Stevens as doing considerable damage 

 in North Carolina, the ray flowers are blighted, resulting in 

 imperfect opening of the buds. Thorough spraying with 

 Bordeaux mixture from the beginning of the season until 



Fig. 219. — Chrysanthemum 

 blossom distorted with ray- 

 blight. Original. 



