28 Howard.—On a Disease of Tradescantia. 
development under the microscope by the hanging-drop 
method, and subsequently to attempt infection experiments 
on healthy host-plants. 
In addition to the above symptoms, many of the still green 
leaves showed pale areas, as if the chlorophyll was being 
decolourized, and on some of these the microscope showed 
minute brown spots and, here and there, fungal hyphae. 
Preliminary plate-cultures were made, using a food-material 
consisting of ten per cent, saccharose-gelatine, containing 
yeast-extract to supply the necessary mineral food materials. 
This medium was only used for one series of plates, as it 
was found to contain dead yeast-cells, and was consequently 
unsuitable for use in hanging-drops—it being difficult to 
determine when the drop contained a single spore of the 
Fungus under investigation. Subsequent cultures were made 
with ten per cent, saccharose-gelatine containing Klebs’s 
solution:— 
/'Potassium nitrate 2 grams per litre, 
j Magnesium sulphate i „ „ 
1 Potassium phosphate 2 „ „ 
which was found to be suited to the needs of the Fungus. 
One of the third series of plates was found to be pure, and 
from this hanging-drops were prepared. Some difficulty was 
experienced in obtaining the Fungus free from a species of 
Cladosporinm or Hormodendron —a significant fact in view 
of subsequent observations—the peculiarities of which were 
studied later, and will be described below. 
In the hanging-drops and on the plates the spores ger¬ 
minated in less than twenty-four hours, and in thirty hours 
colonies were visible with the naked eye on the first of a 
series of plates. In four days conidiophores were visible. 
The details of germination are shown in the drawings 
(Figs. 1-3), and those of spore-formation in Figs. 4-6. 
The hyphae are septate and copiously branched, averaging 
4-5/x in diameter, and creeping horizontally: they throw 
up long conidiophores (Figs. 10, 11), each consisting of a 
