300 DISEASES OF CULTIVATED PLANTS 



Teleutospores form large, elongated, black sori. Spores 

 elliptical, ends rounded, much constricted at the septum, 

 blackish-brown, 45-65x15-25 /*, pedicel very long, firmly 

 attached. 



Onion rust (Pucdnia porri, Sow.) sometimes proves very 

 destructive to onions, both wild and cultivated ; chives are 

 also attacked. Numerous brown, thin, blackish streaks are 

 present on the leaves, which become yellow and die before 

 the bulb is matured. The four spore forms are produced on 

 the same host-plant. 



Aecidiospores. Peridia in linear circinate clusters, shortly 

 cylindrical with torn edges. Aecidiospores polygonal from 

 mutual pressure, finely warted, wall colourless, contents 

 orange, 19-28 p diam. 



Uredospores. Sori reddish-brown, linear or oblong, in 

 elongated groups. Spores subglobose or shortly elliptical, 

 very finely echinulate, orange-yellow, 25-30 x 20-27 P" 



Teleutospores. Sori small, bluish-grey, owing to the spore- 

 mass being covered by the translucent epidermis of the host- 

 plant; spores clavate or oblong, slightly constricted at the 

 septum, generally narrowed towards the stem, apex rounded 

 or truncate, smooth, brown, 30-45 X 20-26 ^, pedicel hyaline, 

 elongated but not persistent. 



Mesospores. Numerous, i-celled, often very irregular in 

 form, sometimes thickened at the apex, 25-36x17-23 p, 

 pedicel hyaline, deciduous. 



This is a very difficult disease to treat. Diseased plants 

 should be removed at once, and the land that has produced 

 a diseased crop should not be sown with onions again for 

 some years, otherwise the teleutospores or mesospores that 

 have fallen to the ground along with decayed leaves will 

 endanger a future crop. 



Heteropuccinia. The secondary spores produced by the 

 teleutospores do not infect the same species of host-plant 

 that produces the teleutospores, but a different one which 

 produces spermogonia and aecidia. 



Gooseberry leaf cluster-cups. During certain seasons the 

 leaves and fruit of the gooseberry are studded with orange 

 blotches, bearing the spermogonia and aecidia or cluster- 

 cups of Pucdnia pringsheimiana. When expanded the cups 

 have white, torn edges, and are filled with orange spores. 



