284 Transactions British Mycological Society. 
interference with the conduction of water, but rather to the 
action of some toxic substance secreted by the mycelium and 
taken up in the transpiration current. 
Thus, Johnson (1) writing on the Fusarium wilt of tobacco says 
‘nevertheless, from the behaviour of the diseased plants, es- 
pecially with regard to yellowing and early turgidity, it is not 
believed that death of the plants is due to clogging of the vessels 
but rather to toxic materials formed by the parasite, or as a 
result of parasitic action on the host.’’ Cromwell (2) investigating 
the Fusarium blight of the Soy bean says, “‘it seems, therefore, 
that the symptoms produced result not simply from a me- 
chanical clogging,’’ and he goes on, “‘a reduction of the activity 
of the protoplasm due to the possible presence of toxins secreted 
by the fungus....” 
Little work has yet been done on the actual isolation of such 
a substance. Hutchinson(3) showed in the case of Bacillus 
solanacearum that the toxin secreted by the bacilli in pure 
culture could be filtered off and when introduced into a living 
tobacco plant would produce the symptoms of the disease. 
Quite recently Young and Bennett (4) working with a Fusarium 
isolated the lethal principle by precipitation with alcohol, re- 
dissolved it in water and showed that the solution still possessed 
its poisonous properties. Professor V. H. Blackman has in- 
formed me that similar results have been obtained at the 
Imperial College of Science, but these have not been published. 
The Michaelmas Daisy disease is due to a parasitic fungus 
which for the present is regarded as a species of Cephalosporium, 
as only its conidial stage has been ascertained. The fungus has 
the property of growing in a watery medium in the form of a 
slimy sheet of mycelium with the copious production of minute 
conidia. 
The cultures were made in 500 cc. flasks containing in one 
series 200-300 cc. of sterilised water (distilled) and some flamed 
pieces of diseased Aster stems, long enough to rest against the 
sides of the flask above the surface of the liquid, and in another 
series 200-300 cc. of distilled water together with similar pieces 
of healthy Aster stems. The flasks of the second series were 
steamed for three hours and when cool were inoculated with 
mycelium from an agar plate culture. In both series the 
Cephalosporium mycelium grew downwards on to the surface 
of the liquid and in four weeks became visible as a thin slimy 
sheet, the liquid also had become brown in colour and re- 
sembled tea in appearance. After being drawn through a 
Berkfeld filter by a water pump, the liquid thus freed from 
conidia, and therefore sterile, was poured into a series of small 
sterilised glass bottles. Another series of similar glass bottles 
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