ON COMPOSITE 145 



19. Puccinia obtegens Tul. 



Caeoma obtegens Link, Obs. ii. 27. 



Trichobasis suaveolens Lev. ; Cooke, Handb. p. 530 ; Micr. Fung. 



p. 226, pi. vii. figs. 151—3. 

 Puccinia obtegens Tul. Ann. Sci. Nat. ser. 4, ii. 87 (1854). Sydow, 



Monogr. i. 53. 

 P. suaveolens Host. Bot. Zeit. 1874, p. 556. Plowr. Ured. p. 182 p.p. 



Sacc. Syll. vii. 633 p.p. Fischer, Ured. Schweiz, p. 219, f. 172. 



Spermogones. Chiefly hypophyllous, a few epiphyllous, 

 crowded, covering the whole surface of the leaf, of a bright 

 honey-yellow colour and a pleasant smell. 



Uredospores. Primary sori hypophyllous, occupying the 

 whole surface of the leaf, minute, crowded, often confluent,, 

 pulverulent, reddish-brown, then darker ; secondary, more scat- 

 tered ; spores globose to broadly ellipsoid, echinulate, pale- 

 brown, 21 — 28 fx, with three irregularly placed germ-pores. 



Teleutospores. Sori similar, always dark-brown ; spores 



ovate to ellipsoid, rounded at both ends, or 



somewhat tapering below, not thickened 



above but with a low flat pore-cap, hardly 



constricted, delicately verruculose, brown, 



26 — 42 x 17 — 25/Z; epispore thin; pedicels 



hyaline, thin, short. 



Fig. 97. P. obtegens. 

 On Cirsium arvense (Carduus arvensis). Teleutospores. 



Very common. (Fig. 97.) 



The life-history of this species is peculiar. In spring the mycelium 

 permeates the host in every part. The affected plants can be recognised 

 immediately by their pale-green colour and spindly appearance ; they 

 never flower. The spermogones are first seen towards the end of April, 

 and are easily detected by their bright colour, and their strong perfume, 

 resembling that of privet-flowers ; the uredospores follow on the same 

 leaves during May. From these primary uredospores, a second generation 

 arises on other plants about July, and forms secondary uredospores and 

 telexitospores in sori which are more scattered, never confluent, and 

 darker brown. This generation is not accompanied by spermogones. 

 The mycelium of these sori is localised to the infected spots and the host 

 does not suffer so severely. The sori of the primary uredospores rarely 

 bear a few teleutospores intermixed, but the secondary sori abound with 

 them from .September to November, and it is from the germination of 



G. U. 10 



