52 FUNGOID PESTS OF CULTIVATED PLANTS. 



SENECIO BUST. 

 Coleosporium Senecionis (Pers.), PI. III. fig. 61. 



A common bright orange rust is to be found every season on the under 

 side of the leaves of the Common Groundsel and other indigenous species 

 of Senecio. Occasionally the same species makes its appearance in gardens 

 on the leaves of cultivated species of the same genus, such as Senecio 

 pulcher and S. sarracenicus. 



Theorists tell us that the aecidiospores of this pest are produced on the 

 leaves and twigs of certain conifers, which, not being garden flowers, may 

 here be excluded. Even the believers are a little sceptical, for Plowright 

 says : " I have had so many failures in infecting Senecio vulgaris with 

 the secidiospores from Fir trees that I think there must be more than one 

 species." 



The pustules of the Uredo are reddish-yellow, soon becoming paler and 

 powdery. Uredospores shortly catenulate, or growing in chains, then 

 separating, elliptical, ovoid (20-40 x 14-26 /*), warted, orange. After- 

 wards teleutospores are said to be produced in other darker- coloured 

 pustules. Teleutospores cylindrical (110 /* long), for the most part divided 

 transversely into four cells of an orange-red colour. 



We can suggest no remedy, except prevention, by keeping all wild 

 species of Eagwort at a distance and destroying infected plants, as the 

 garden forms are not apparently so susceptible to the disease. 



Universally diffused through Europe. 



Sacc. Syll vii. 2683 ; Mass. PL Dis. 261 ; Cooke M.F. 97, 218, 

 figs. 145, 146 ; Tubeuf, Dis. 374, fig. ; Plowr. Brit. Ured. 240. 



Recently ^Ecidium Cineraria has been detected in Austria on leaves 

 of Cineraria. 



PTAKMICA DOT. 

 Schizothyrium Ptarmica (Desm.). 



Plants of Achillea Ptarmica are to be met with in old-fashioned 

 gardens, and the green leaves are liable to the attack of a special fungus. 



The leaves and stems are at first dotted over with the small black 

 points of Leptothyrium Ptarmica. These minute black receptacles con- 

 tain a number of oblong sporules, with an apparent central division 

 (10 x 6-7 /u). This is regarded as an early and imperfect condition of a 

 more highly developed parasite, which resembles it in size and appearance, 

 and often grows in company with it. 



This latter, or Schizothyrium, came over from France with imported 

 plants many years ago. To the naked eye they look like fly spots, causing 

 no discoloration of the foliage. The receptacles are flattened and open on 

 the upper surface, enclosing minute ovoid sporidia (10 p. long), enclosed in 

 asci, closely packed side by side in the interior. It has evidently a 

 perennial mycelium, since the dots or receptacles will continue to appear 

 on the same plant year after year for many years. The plants are stunted, 

 tut not much disfigured by the parasite. 



The disease is known in France, Belgium, Germany, Finland, and 

 Siberia. 



Sacc. Syll. ii. 5559, iii. 3379. 



