L52 PUCCINIA 



I redosjx.res. S«»ri hypophyllous, on pallid irregular spots, 



scattered, minute punctiforra, pul- 

 verulent, pallid-brown : spores more 

 or less globose, echinulate, yellow- 

 brown, lb' — 24 fji. with three (rarely 

 four) germ-pores. 



Teleutospores. Sori similar, 



surrounded bv the cleft epidermis, 



"tSU'JSSSS-.* blackish-brou",, : spores ellipsoid, 



rounded and not thickened above, 

 not constricted, rounded below, very delicately verruculose, 

 brown, 26 — 36 x 16 — 24 /x ; pedicels hyaline, very short. 



On Lactuca (Prenanthes) muralis only. Not common. 

 April — September. All three spore-forms may be found on the 

 same leaf. (Fig. 104.) 



The secidium of this species is not provided with a proper peridium 

 and opens with a pore, never assuming the form of a cup ; moreover the 

 secidiospores are more round than angular. The germ-pores of the uredo- 

 spores are covered with a broad convex colourless cap, which swells up 

 somewhat in water. The genetic connection of the three spore-forms has 

 been proved experimentally by Jacky (Ceutralbl. f. Bakt. ix. 1902, p. 842), 

 as also the fact that the parasite is not transmissible to other specie 

 Lactuca. There is another secidium also found on Lactuca mnralis on the 

 continent which possesses a well-developed peridium ; this belongs to 

 Puccinia Opizii Bubak, and has its teleutospores on Carex muricata. 



Distribution : Europe generally. 



27. Puccinia variabilis Grev. 



JEJcidium Grevillei Grove, Journ. Bot. 1886, p. 129. 



Puccinia variabilis Grev. Scot. Crypt. Fl. pi. 75. Cooke, Handb. 



p. 500 ; Micr. Fung. p. 207, pi. 4, f. 82—3. Plowr. Ured. p. 150. 



Sydow, Monogr. i. 163. Fischer, Ured. Schweiz, p. 202, f. 158. 



jEcidiospores. iEcidia amphigenous, on minute indetermi- 

 nate yellow or purplish spots, solitary or a few loosely aggre- 

 gated, cup-shaped, with whitish torn margin; spores subglobose 

 or ovate, with orange contents, verruculose, 20 — 25 x 15 — 20 /x. 



Uredospores. Sori amphigenous, on very minute yellow or 



