Life-history of Parasitic Fungi . 367 
Before discussing the relations of the two conidial forms, Cladosporium 
and Hormodendron , to each other, it may be well to describe briefly the 
experiments which were conducted on the infection of living leaves with 
conidia of Cladosporium. For this purpose excised leaves were used, and 
the experiments were conducted in a similar way to those described above 
in which the leaves were placed on filter papers in Petri dishes, and the 
conidia transferred to definite spots on them by means of a needle. The 
conidia were taken from the leaves of Catalpa and of Cabbage. After four 
days an examination of the spots showed that conidia of Hormodendron 
were being produced; later on, the leaves died and commenced to rot, and 
the conidia of Hormodendron ceased to be formed ; conidia of Cladosporium 
were then found to be present in abundance. The infection of the leaves 
of Cabbage and Catalpa yielded similar results, and led to the following 
conclusions :— 
Conidia of Cladosporium placed on living leaves give rise to conidia of 
Hormodendron which are capable of infecting living leaves ; direct infection 
by conidia of Cladosporium is not possible when the leaves are living; 
when the leaves die, Hormodendron disappears, and Cladosporium then 
makes its appearance. 
The relations of Cladosporium and Hormodendron to each other 
and the nature of the life-cycle. 
It has been shown above that if healthy leaves are infected artificially 
with conidia o iHormodendron> they develop symptoms of disease which are 
similar to the symptoms observed in the case of leaves which have been 
infected naturally with Hormodendro7i. It is, therefore, concluded that 
Hormodendron is capable of living as a parasite on the green leaves of 
plants and of causing disease. 
Hormodendron attacks many plants which exhibit no close relationship 
to each other; in its range it is not confined to species of one family 
or even of closely allied families, and it can be transferred from one 
species of host to another without any difficulty. This shows that it is 
only weakly parasitic, in the sense that it represents no highly developed 
form of parasitism. 
The cultural experiments have shown that the same mycelium which 
had previously formed conidia of Hormodendron gives rise later to conidia 
of Cladosporium , while observations on the leaves of plants attacked by 
Hormodendron in nature have shown that when the leaves commence 
to wane and die Hormodendron disappears, and Cladosporium makes its 
appearance. It is inferred that Cladosporium occurring on waning or dead 
leaves has its origin from Hoi'modendron which attacks the leaves when 
they are living. Also, since on the dead leaves Hormodendro7i passes 
