78 FUNGOID PESTS OF CULTIVATED PLANTS. 



this species, as its appearance will now be problematical after so many 

 years of absence. 



CooJce Hdbk. No. 1611 ; Sacc. Syll. vii. 2962 ; Plowr. Brit. Ured. 266. 



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

 maculatum, and another species (JEcidium aroideum) which occurs in 

 Natal, are apparently quite distinct. 



CALLA SOFT HOT. 

 Bacillus AroidecB (Town.). 



This disease has recently been investigated in the United States, and 

 declared to be Bacterial. The same organism is declared to be capable 

 of attacking a large number of vegetables. It occupies the intercellular 

 space in its host, and dissolves the layers which connect the cells, causing 

 the tissue to break down into a soft slimy mass. No successful treatment 

 discovered. Journ. R.H.S. xxix. 1905, p. 761. 



FERN DISEASES. 



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

 few and unimportant, although several are recorded abroad. 



DAMPING OFF. 

 Pythium 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 it 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. PL Dis. 350. 



FERN BUST. 

 Uredofilicum (Desm.), PL IV. 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 (22-85 x 13-20 ^u), the other somewhat angular with a thick 



