JEHANGIR FARDUNJI DASTUR. 191 



atmosphere by covering it with a bell jar. The next day the 

 inoculated leaf was plucked and immersed in 2o per cent, formalin 

 for half an hour, it was then well washed with sterilised water and 

 transferred to a sterilised covered Petri dish containing a little 

 sterilised tap water. From the inoculated spot an aerial mycelial 

 growth of Phytophthom, free from other fungi but not from bacteria, 

 developed in 24 to 48 hours. It was found essential to keep the 

 leaf in contact with water to get the aerial growth. A portion of 

 the aerial mycelium was then transferred by means of a sterilised 

 platinum needle to a piece of pith soaked in Ricinus leaf juice 

 prepared as follows : About 10 to 15 grammes of green castor leaves 

 were boiled for an hour in 100 c.c. of distilled water. One or two 

 pieces of pith in an Erlenmeyer flask were soaked in some of the 

 filtered decoction, enough to leave very little of it at the bottom 

 of the flask after sterilisation. After two or three days a sparse 

 woolly growth projected about a centimetre high from the upper 

 surface of the pith. These hyphge were free from bacteria and 

 bore no sporangia except occasionally in old cultures, but when a 

 bit was transferred to water, it bore innumerable sporangia the next 

 day. If the flask contained much liquid the pith was soon over- 

 grown with bacteria and the growth of the fungus retarded. It 

 was now only necessary to inoculate a suitable culture medium with 

 a bit of the mycelium growing on the pith. Such a medium was 

 found in French bean (Phaseolus vulgaris) juice agar which gave 

 in two days a pure, rich, healthy culture. 



Morphology of the Fungus in Culture. 



The comparatively young mycelium consists of thin, not much 

 branched, unseptate hyphae. The protoplasm within them is 

 finely granular ; but as they grow older they become very broad, 

 up to 9/a ; the granules become coarser and aggregate into groups 

 or irregular masses, the contents lose their homogeneity ; at a still later 

 stage septa are formed, but they are far between. In very old cul- 

 tures they are formed fairly frequently. In these cultures branches 

 have been found to be rather uniformly cut off from their mother 



