164 MANUAL OF FRUIT DISEASES 
ment may consist of short, slender twigs. Sometimes one 
healthy shoot is found among diseased ones. Shoots of brooms 
will frequently remain green after old canes are dead. When 
flower-buds open, they display various malformations: some- 
times the deformity is slight, again extensive, depending some- 
what on the extent of infection. Blossoms are usually affected, 
the sepals and petals being thickened. Some growers errone- 
ously regard these diseased blossoms as male flowers. At 
times the blossoms are increased in numbers; this is especially 
true of the petals. Diseased petals have the appearance of 
being doubled, whence the name double-blossom. Other parts 
of the flower may show abnormal growth, due to the double 
blossom pathogene. The stamens and ovaries are affected. 
It happens at times that certain flowers appear healthy, but such 
flowers may have diseased ovaries. Every bud in an affected 
plant may be diseased. Sometimes late blossoming is induced 
in plants attacked by the double-blossom parasite. In such 
cases the blossoms are smaller than normal. 
Cause. : 
The abnormal bud-development just described is due to the 
fungus Fusarium Rubi. In the early spring its mycelium may 
be found between the parts of affected buds. With the advent 
of proper conditions growth is resumed. The mycelium does 
not pass from the bud into the stem. It does, however, 
enter certain parts of the bud. The ovaries are penetrated by 
way of the stigma and the style. An abundant growth of 
mycelium takes place within these organs, but the carpels and 
ovules are not penetrated. Neither are the stamens penetrated, . 
although the hyphe may be found abundantly between them. 
Wherever the mycelium enters the tissues of a bud, haustoria 
are sent into the cells. Thus the fungus feeds on its host, stimu- 
lating the leaf-buds to witches’-broom formation, and dwarfing 
the ovaries of the flowers. This influence is also felt by other 
parts of the flower, as noted under Symptoms. 
