COLEOSPORIUM 



321 



/Ecidia on (?one of the two) leaves of Pinus austriaca, 

 P. silvestris, May, June ; uredo- and teleutospores on Senecio 

 Jacobaea, S. palustris, 8. silvaticus, S. viscosus, S. vulgaris, all 

 through the year; also recorded for S. pulcher, S. sarracenicus, 

 etc., in Botanic gardens, and on cultivated Cinerarias (i.e. 

 Senecio) at Sydenham; see Journ. Roy. Hort. Soc. 1908, xxxiii. 

 511. Very common. (Figs. 241, 242.) 



Fig. 241. C. Senecionis. a, chain 

 of uredospores ; b, two fascicles 

 of leaves of P. silvestris, bearing 

 peridia on one leaf only of each 

 fascicle (reduced). 



Fig. 242. C. Senecionis. Teleuto- 

 spore germinating. 



This is the species of Coleosporium whose life-history has been longest 

 known ; Wolff first experimentally demonstrated it in 1872, and he was 

 followed by Plowright in 1882, as well as by Cornu, Hartig, Rathay, Von 

 Thiimen, Rostrup, Klebahn and Fischer. The secidium had previously 

 been called Peridermium. Since Senecio vulgaris continues to live through 

 the winter in our climate, and Magnus and others have found the uredo- 

 spores throughout the year, the intervention of the alternate host is 

 not in this case necessary. Yet it is generally quite easy to find the 

 Peridermium on the needles of P. silvestris if one searches in June any 

 trees that may be growing in the neighbourhood of Groundsel infected 

 with the parasite ; since the Peridermium is not conspicuous, it may easily 

 be overlooked unless special search is made. It is probable that there are 

 several biological races of this fungus, on different species of Senecio, and 

 it has been proved by Fischer that it cannot be transferred to Cacalia or 

 Sonchus. 



G. U. 



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