44 E. J. BUTLER. 
types of soil fungi can be considered a proved parasite unless success- 
ful inoculations have been obtained in each case with pure cultures 
of the fungus concerned. The mere presence of a fungus in the 
tissues of the diseased plant with conidial stages agreeing with 
those of a recognised parasitic form of Cephalosporium or Fu- 
sarium counts for nothing without successful cultivation and 
inoculation. 
Description of the parasite of pigeon-pea wilt. 
The characters of the internal growth in diseased roots have 
been described in the previous paper. When such roots are well 
washed, flamed and placed in water on a slide, an external growth 
appears on the surface in a day or two. This has at first consisted 
only of the Cephalosporium type m the cases observed, but subse- 
quently Fusarium spores appear. The Cephalosporium is charac- 
terised by a rather scanty creeping mycelium, with very many short 
conidiophores, often whorled, and bearing great numbers of micro- 
conidia. There is ordinarily little tendency for the growth to extend 
into the air; most of the conidiophores remain immersed in the 
liquid and therefore do not show the characteristic heads of spores 
bound in a drop of water. These occur, however, in cultures on 
solid media and may be studied in agar drop cultures on slides or in 
glass cells (plate IV, fig. 3). 
The following description is taken from pure strong cultures 
of the fungus, the parent of which or subcultures from which have 
been proved to be parasitic by inoculation. The cultural charac- 
ters on different media will be given in detail below. 
The hyphe are fine, copiously branched, septate and colourless 
under the microscope. Anastomoses occur rarely in vigorous cul- 
tures, but are common when a portion of the growth in an old culture 
is sown in water, and also between the germ tubes of both sorts of 
conidia (plate IV, fig. 10). Cephalosporium spores begin to form 
when the mycelial growth is still scanty, and are found in great num- 
bers by the third day in most good cultures. Singly they are 
