DISEASES OF PLANTS. 27 1 



are affected, the softened spots will dry up, sinking below the surrounding portion 

 of the conn, and in these places the organism causing the disease will remain dormant 

 until the conditions for its development again become favorable. In this way the 

 " disease is carried over from season to season and may be transported over long 

 distances. 



A microscopical examination of the affected parts shows an abundance of bacteria 

 and the morphological characters of the organism and its physiological character- 

 istics, as shown when grown on different media and under varying conditions, are 

 described. Comparisons have been made between the organism causing this disease 

 and those known to cause a number of similar plant diseases, but the organism of 

 the calla lily differs very materially from the others and it is proposed, therefore, to 

 call it Bacillus aroidex n. sp., the technical characters of which are given. 



The origin and spread of the disease are described, and it is said that the spread 

 from plant to plant within the house seems to be accomplished mainly through the 

 soil. The spread of the disease over long distances is accomplished as described 

 above. The nature of the soil seems to have an influence on the spread of the 

 disease, as soils rich in vegetable matter, filled with humus, and containing a large, 

 amount of moisture favor the rapid multiplication of the organisms. 



Experiments were conducted with a number of fungicides for preventing the 

 disease, none of which were entirely successful. The application of lime and lime 

 and sulphur retarded the progress of the disease and in a few cases seemed to have 

 entirely eradicated it. As the disease did not seem to be controlled by the usual 

 methods of attention to the soil, it was found that by changing the soil every 3 or 4 

 years and carefully selecting the conns for planting, the disease may be held in check. 

 The organism causing this rot was found able to attack a large number of raw vegeta- 

 bles, producing a soft rot in them, and on this account care should be taken not to 

 throw any decayed or partly decayed callas where vegetables are stored or grown. 

 It does not attack tree fruits readily, and is not likely to produce fruit rots. 



Diseases of ginseng-, J. M. Van Hook (New York Cornell Sta. Bui. 219, pp. 165- 

 186, Jigs. 25). — It has been generally claimed that the ginseng plant is practically 

 free from fungus enemies, and, while this may be true in a wild state, a single sea- 

 son's study of the cultivated plant has shown that it is subject to a number of very 

 serious diseases. One of the most destructive is the wilt of the old ginseng plants, 

 which may be readily recognized by the wilting of the foliage and the discoloration 

 of the roots and rootstocks when observed in section. This disease is attributed to 

 a species of Acrostalagmus, which, while slightly differing from A. albus, is not 

 considered sufficiently different to warrant its description as a new species. The 

 investigations so far carried on with this disease seem to indicate that it spreads 

 through the soil and that probably by the selection of resistant varieties it can be 

 most profitably combated. 



Wilts of seedlings are also described, one of which results in the damping off of 

 young plants caused by attacks of Rhizoctonia. In a second, which is called an end 

 rot, the lower end of the seedling is involved, the root shrivels, and the stalk and 

 leaves finally die, while a third form, which has been known to cause serious loss, 

 especially in the seed beds, is due to species of millipedes. 



Ginseng is also reported to be subject to attacks of nematodes, which produce their 

 characteristic effects upon the roots. Where the ground is open and subject to heavy 

 freezing, there is not believed to be much danger from this pest; but where it receives 

 mulching or protection from the cold, the freezing will not destroy the nematodes. 



A black rot of ginseng due to a species of Alternaria is described, as well as a soft 

 rot which has not yet been definitely determined as due to any specific cause. In 

 the soft-rot disease the roots decay very rapidly, becoming sticky and ill-smelling. 

 A species of Fusarium, as well as bacteria, are usually present in great abundance, 

 and the foliage is attacked by a species of Botrytis, but as yet the definite cause of 



