ON VIOLA 



203 



On Viola cornuta, V. lutea, V. tricolor, and most of the 

 many hybrid Violas and Pansies now cultivated in gardens. 

 Fresh ascidia are formed right through the summer till August, 

 while those of P. Violae cannot usually be found after early 

 June. (Fig. 150.) 



The mycelium of the ajcidia is perennial in the underground parts ; all 

 the shoots which arise from the affected plant are deformed, the internodes 

 are lengthened, the leaves become smaller, paler and often twisted. In 

 P. Violae this is not the case ; only a slight swelling arises at the part 

 where the localised mycelium is producing its eecidia. Bock (Centralbl. 

 fiir Bakt. 2. xx. 586) found that he could produce the pecidia of P. Violae 

 on the three species of Viola named above, by artificial infection ; but like 

 others he still considered the two species as distinct on account of their 

 different habit. Liro, on the contrary, considers them as the same. In 

 my experience, the uredo- and teleuto-sori of P. aegra are larger, and 

 remain longer covered by the epidermis, but the spores are identical. 



This species can do considerable harm if allowed to spread ; there is 

 no remedy, but all infected plants should be carefully uprooted and burnt. 

 A Viola, badly attacked by the recidium, was once sent to the Gardener's 

 Chronicle by a correspondent as " a hybrid between a fern and a violet." 



Distribution : Germany, Denmark. 



75. Puccinia Fergussoni B. et Br. 



Puccinia Fergussoni Berk, et Br. Ann. Nat. Hist. 1875, p. 35. Cooke, 



Grevillea, iii. 179, pi. 49, f. 10 c ; Micr. Fung. p. 210. Plowr. 



Ured. p. 207. Sacc. Syll. vii. 682. Sydow, Monogr. i. 444. Grove, 

 Journ. Bot. 1912, p. 10. 



Teleutospores. Sori hypophyllous or on the petioles, on 

 large roundish or irregular yellow spots, 

 in suborbicular or (on the petioles) elon- 

 gated clusters up to 1| cm. long, densely 

 crowded and confluent, long covered by 

 the epidermis, then pulverulent, choco- 

 late-brown; spores irregular, generally 

 oblong, attenuated or rarely rounded at 

 both ends, thickened above in a conical 

 form (up to 6 ll), gently constricted, 

 smooth, pale-brown, 26 — 45 x 12 — 18 //.; pedicels hyaline, thin, 

 deciduous, up to 30 fx long ; an occasional mesospore is found. 



Fig. 151. P. Fergussoni. 

 Teleutospores and me- 

 sospore. 



