The Fungus Pests of certain Flowers 



viola, which is apparently identical, however, with Pucdnia 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 pustules, each pustule less in size than a 

 pin's head, and all congregated into one flat circular mass of about a 

 quarter of an inch in diameter. This pest is very frequent on the 

 Dog Violet, 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 

 of the most destructive pests 

 of Violas is found in ALcidium 

 depauperans, so called because 

 its effect is first to starve and 

 attenuate, and then to totally 

 destroy, plants of Viola cornuia. 

 It is a close ally of ^. viola, 

 but it differs in having its 

 minute cups or pustules ir- 

 regularly distributed all over 

 the green parts of the host- 

 plant instead of being congregated in circular patches, as in &. viola. 

 Our illustration shows, at A, a small portion of the stem of Viola 

 cornuta attacked by sEridium 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 

 illustrated 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 

 Phyllosticta 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. 



VIOLET DISEASE 



depauperans 



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F F 



