Life-history of Parasitic Fungi . 361 
From the structure and arrangement of the conidia the fungus was found 
to correspond with the form-genus Hormodendron. 
An account will now be given of the infection experiments which show 
that the form Hormodendron is the cause of the disease described above. 
Before actually carrying out the infections a pure culture of the fungus was 
made in order to ensure the exclusion of any spores other than those of 
the form Hormodendron. First, some of the conidia were taken from an 
infected leaf of Catalpa bignonioides and were transferred to pure water in 
a ‘ hanging-drop ’; they were thus kept in water in a chamber which was 
constantly moist. In from one to two days they were found to have 
germinated. Each emitted one hypha, as a rule, which became septate and 
branched ; the absence of food-material prevented any further growth of 
the hyphae. A cultural medium composed of 4 per cent, of the expressed 
juice of fresh grapes and 6 per cent, of gelatine was found to be favourable 
to the growth of the fungus. This nutrient gelatine was sterilized by 
heating in a steam-oven for four hours each day on three successive days. 
Five Petri dishes and a boiling-tube, into which a plug of cotton-wool had 
been inserted so as to close its mouth, were sterilized by heating in an 
air-oven at ioo° C. for five hours each day on two successive days. 
Some of the nutrient gelatine was transferred to the boiling-tube, and to this 
were added some conidia taken from a previously made, impure culture ; 
the needle used for transferring the conidia had been previously heated 
to a red heat and allowed to cool. The liquid in the boiling-tube was 
shaken, and some of it was poured into a Petri dish. The remainder of the 
liquid in the boiling-tube was then diluted by one-half, it was shaken and 
some was transferred to another Petri dish ; this process of diluting, shaking, 
and transferring some of the fluid to a Petri dish was repeated three times. 
Care was taken to keep the boiling-tube closed as much as possible, and 
before removing the plug of cotton-wool the part of the plug which was 
exposed to the air was slightly burnt on each occasion so as to prevent any 
spores which had fallen on it from the air from dropping into the liquid 
in the tube. The last Petri dish was found to contain a pure culture 
derived from the growth of a single conidium. The growth and develop¬ 
ment of the mycelium in the pure culture was carefully followed. The 
hyphae when young were colourless, but as they grew older they assumed 
an olive colour; they were septate at fairly short intervals and were 
variously branched. From them there arose abundant lateral branches 
which grew above the surface of the nutrient gelatine and bore branched 
chains of conidia. The conidia in their structure, mode of formation, and 
arrangement corresponded with those observed on the infected leaves and 
described above. 
Conidia taken from the pure culture were used for infecting living 
plants. Two methods were made use of for transferring them to the leaves ; 
