366 
Bancroft.—Researches on the 
into a chain of conidia. Other ‘ hanging-drop ’ cultures were prepared 
as controls, and were kept at the temperature of the laboratory; in these 
the production of conidia of Hormodendron was found to take place in the 
ordinary way. At the lower temperature, then, the formation of conidia of 
Hormodendro7i was completely suppressed. 
The microsclerotia of Cladosporium; their growth and development. 
Each tuft of conidiophores of Cladosporium springs from a cellular 
mass produced by the approximation and repeated division of the hyphae. 
When the conidiophores fall away this mass of cells remains and forms 
what has been called a microsclerotium. The microsclerotium is somewhat 
rounded and measures, when fully formed, about 160 n across. Its surface 
is corrugated, and there can be seen projecting from the main mass a few 
outlying cells which are more or less transparent. The main mass of the 
microsclerotium is black or of a very dark brown colour, and is composed 
of cells which are more or less rounded, dark bn wn in colour, and have 
rather thicker walls than the hyphae from which mey were formed. It is 
conceivable that the microsclerotia do not necessarily always arise at the 
base of a tuft of conidiophores ; the hyphae in the tissues, in their later 
stages at any rate, show a tendency to form masses of cells, and these 
probably also develop into microsclerotia. The microsclerotium is regarded 
as a resting-stage of Cladosporium , or rather as a stage which is capable of 
enduring a period of inactivity. 
The growth of microsclerotia taken from leaves of Oak, Catalpa y 
Cabbage, Funkia , Plantain, and other plants, was observed; they were allowed 
to germinate in ‘ hanging-drops ’ in water. Each superficial cell by the 
rupture of its thick wall was found to be capable of emitting a hypha ; the 
hypha grew, became septate, and seldom brand 1 . From its tip there 
arose a short chain of conidia of Cladosporium. The microsclerotium was 
thus seen to be capable of producing conidiophores which bore conidia of 
Cladosporium, and this was found to occur in the case of all of the species 
of plants used. Some of the smaller masses of cells had been seen, as was 
stated above under the section dealing with the origin of Hormodendron 
from Cladosporium , to give rise to conidia of Hormodendron , but these are 
not regarded as fully formed, true microsclerotia. 
Some of the conidia of Cladosporitim derived from microsclerotia were 
germinated in £ hanging-drops ’ in a 2 per cent, solution of cane sugar; 
they were found to give rise to conidia of Hormodendron. This was 
observed in the case of conidia produced by microsclerotia which had been 
taken from all of the species mentioned above. It is, therefore, concluded 
that this is the means by which Hormodendron is naturally regenerated 
in the spring. 
