414 THE FUNGUS PESTS OF CERTAIN FLOWERS 



X-6o 



as Trichobasis or Uredo violarum. In spring and early summer, 

 Violets are often badly affected by a fungus named jEcidium viola. 

 This disease attacks leaves, stems, and sepals, and it is best examined 

 on the leaves. In this position it is seen to consist of a considerable 



number of minute yellow pus- 

 tules, each pustule less in size 

 than a pin's head, and all con- 

 gregated into one flat circular 

 mass of about a quarter of an 

 inch in diameter. This pest is 

 very frequent on the Dog Vio- 

 let, but it is perhaps equally 

 common on the Sweet Violets 

 of our gardens in early spring, 

 and it not unfrequently spreads 

 to other species of Viola. One 



VIOLET DISEASE Qf ^ ^^ destructive pCStS 



Mcidium depaupcrans r AT- i r -, ^ -j- 



of Violas is found in ALadium 



depauperanS) so called because its effect is first to starve and 

 attenuate, and then to totally destroy plants of Viola cornuta. It 

 is a close ally of SE. viola, but it differs in having its minute cups 

 or pustules irregularly distributed all over the host plant instead of 

 being congregated in circular patches, as in ^. viola. Our illus- 

 tration shows, at A, a small portion of the stem of Viola cornuta 

 attacked by sEcidium depauperans. The minute pustules are seen 

 (natural size) distributed all over the stem, leaf-stalks, and ruined 

 leaves ; the effect of the fungus growth is to decompose the tissues 

 of the plant. At B, a transverse section through the stem is illus- 

 trated and magnified twenty diameters. The section cuts through 

 several of the abscess-like pustules, and it is seen how completely 

 embedded they are in the flesh of the plant. At C, a pustule is 

 seen in section, enlarged sixty diameters, to show more clearly the 

 innumerable spores, or seeds, disposed in necklace-like fashion, 

 which are destined to reproduce the pest in future seasons. Another 

 disease of Violets in autumn is caused by a fungus named Urocystis 

 viola. This fungus causes gouty swellings to form on the stalks 

 and principal veins. These swellings at length burst, exhibit black 

 patches, and discharge sooty spores. The fungoid disease named 

 Phyllostica viola is frequently common on Violet leaves in June. In 

 this the spots are whitish. No cure is known, and it is always well 

 to burn or deeply bury all infected leaves or plants. 



