RUSTS. 99 



minute^ cellular, linear bodies called spermatia, in- 

 vested witli a kind of mucous substance, that over- 

 flows witli them from the orifice of the spermogone, 

 like lava from the crater of a miniature volcano. 

 The rust in company with which they have been 

 found most plentifully, is that which covers the 

 under surface of the leaves of the commonest of 

 all thistles {Cnicus arvensis). The external form of 

 ■one of these spermogones is figured plate VII. 

 fig. 153. The rust possesses, when fresh, a pecu- 

 liar odour, which is said to resemble that of orange- 

 flowers ; whence was derived its name of " sweet- 

 smelling rust^' (Trichohasis suaveolens, Lev.). M. 

 Tulasne writes : — " With respect to this species, it 

 is, in my opinion, but the first form of a Pucci7im, 

 analogous to P. Gompositarum, D.C. : the spermo- 

 gones with which it is mixed being very abundant, 

 it ought to be placed with that Puccinia. I should, 

 perhaps, retain some doubts upon the legitimacy 

 of this relationship, if it had not been my fortune 

 to meet on another species of the same kind {Puc- 

 cinia Anemones, P.) spermogones perfectly charac- 

 terized, and in which the colour, habit, and position 

 would not allow me to hesitate an instant in at- 

 tributing them to the Puccinia,'' In this species of 

 rust the whole under surface of the leaf is covered 

 veith a purpHsh-brown dusty coating of the spores, 

 from the numerous pustules which are produced 

 (plate VII. fig. 151). The plants, when attacked, 

 have a paler and more sickly appearance ; the leaves 



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