PESTS OF THE FLOWER GARDEN. 



401 



The ordinary Arum cluster-cups found on the leaves of wild Arum 

 maculatum, and another species {Mcidium aroideum) which occurs in 

 Natal, are apparently quite distinct. 



FERN DISEASES. 



The diseases of hardy Ferns under cultivation in this country are very 

 few and unimportant, although several are recorded abroad. 



Damping off. 

 Pytliium intermedium (De Bary). 



The " damping off " of the prothallia of Ferns is possibly sometimes 

 due only to an excess of moisture ; but an actual disease has been recog- 

 nised in the United States, and there is no reason why ic may not make 

 its appearance amongst us, as the fungus itself is of European origin. 



The affected prothallia become quite soft and limp, and darker in 

 colour than the healthy ones. 



An allied species of fungus is responsible for the " damping off " of 

 seedlings of crucifers, whilst some authors regard them as the same 

 species. 



In structure Pythium resembles a Mucor, and produces resting spores 

 as the result of conjugation, similar to the rot-moulds. 



Bull. U.S.A. Exp. Stn. Cornell Univ. 94, p. 247, pi. ; Bot. Zeit. 

 1881 ; Sacc. Syll. xi. 1400 ; Mass. PI. Dis. 350. 



Fern Rust. 

 Uredo filicum (Desm.), Pl.jV. fig. 79. 



There are two or three kinds of Fern rust known, but only one species 

 appears to be known in Britain, and that is not uncommon in gardens and 

 greenhouses, especially on Cystopteris fragilis, appearing on the under 

 side of the fronds, which consequently assume a sickly appearance. 



The pustules are rounded or irregular, and scattered over the under 

 surface of the fronds in bright yellow spots. The uredospores are powdery, 

 and are of two forms, the one ovate or elliptical and spinulose above, but 

 smooth below (22-35 x 13-20 /u), the other somewhat angular with a thick 

 smooth outer coating (26-38 x 18-29 n), and both of a bright orange 

 colour. 



Ferns on which the rust makes its appearance should be isolated, and 

 the diseased fronds cut off and burnt, whilst the plants so left should be 

 sprayed with Condy's fluid. 



It is distributed through Belgium, Germany, Finland, Austria, 

 Bohemia, Italy, South Africa, and North America, and appears to be the 

 same as Uredo Polypodii (Pers.) 



Sacc. Syll. vii. 3096, xi. 1304 ; Cooke, M.F. 112; Proc. Amer. Acad. 

 1894, p. 396 ; Cooke Hdbk. No. 1569 ; Ploiur. Br. Ured. 256. 



Uredo Aspidiotus in the United States appears to be different, as also 

 Uredo Pteridis in California, and Uredo Scolopendri in Germany and the 

 Netherlands. 



i) 



