334 DISEASES OF CULTIVATED PLANTS 



in spring on the needles of the Scots fir and other conifers. 

 The aecidiospores infect groundsel and other wild and 

 cultivated species of Senea'o, and also Cineraria, which is 

 botanically a Senea'o. 



Saccardo and others, on the other hand, consider the 

 fungus present on Cineraria to be Coleosporium sonchi (Lev.). 

 Infection experiments can alone settle this point. 



The following is the description of Coleosporium senecionis. 



Spermogonia scattered ; aecidia of two forms, one solitary 

 or few in number, on the leaves, cylindrical, up to 2-5 mm. 

 long; others on the bark, often 6 mm. broad, saccate, 

 crowded, white, becoming torn, spores various in form, up to 

 40 X 17-28 /i, warted, orange. 



Uredospores. Sori yellowish-rufous, soon pale, pulveru- 

 lent ; spores in short chains which soon break up, elliptical 

 or sub-cylindrical, orange, warted, 20-40 x 14-26 /*. 



Teleutospores forming waxy, compact sori, slightly convex, 

 yellowish-rufous, then red ; spores cylindrical, or cylindric- 

 clavate, closely packed side by side, generally 3-septate, 

 bright rufous-orange, apex flattened. 



Chittenden, F. ).,Jour. Roy. Hort. Soc, 33, p. 511. 



Aecidium cinerariae, reported as occurring on leaves of 

 Cineraria in Austria, judging from the description, is not 

 likely to be met with again. 



CHRYSOMYXA (Unger) 



Teleutospores transversely many -septate, arranged in a 

 single series like palisade tissue, sometimes branched, lower 

 cells sterile, coalescing in a waxy convex mass ; uredospores 

 as in Coleosporium, aecidia as in Puccinia. 



Rhododendron rust {Chrysomyxa rhododendri, De Bary). 

 The uredo and teleutospore stages develop on the leaves of 

 Rhododendron hirsutum and other species, where they form 

 small pustules. The aecidium condition occurs on young 

 shoots and leaves of the spruce fir. Yellow spots appear on 

 the leaves, and about the month of August the spermogonia 

 appear on these spots ; at a later period the aecidia are 

 developed, and contain such an immense number of spores 

 that when a diseased tree is shaken, the air is filled with a 

 dense cloud of spores. Diseased leaves die and fall the 

 same season. 



