214 PHYTOPHTHORA PARASITICA. 



sufficient quantity of water to bring the whole up to 500 c.c. The mix- 

 ture was brought to the boil and strained through linen before rilling 

 the tubes. The aerial growth was copious but at first sterile, sporangia 

 were formed after a week. Submerged hyphie were irregularly swollen. 



Maize corn meal. — This medium was prepared by adding to the 

 meal a sufficient quantity of water to keep the medium moist 

 after it was autoclaved. The fungus growth was very good. A 

 rich crop of sporangia was obtained. 



Potato juice agar (150 + 10 + 500). — Growth in this medium was 

 not localised ; it was mostly in the substance of the medium and there 

 was a very sparse aerial growth. The submerged mycelium differed 

 from the aerial in being broader and irregularly branched. Sporangia 

 were formed freely both in the aerial and submerged mycelium but 

 none of these were found to produce zoospores. They germinated 

 conidially without falling off from their conidiophores. They were 

 abnormal both in size and shape and contained a lot of oil globules ; 

 an extreme measurement was 110 to 35 M (Plate V, Fig. 14), but when 

 a bit of the mycelium was transferred to water normal sporangia 

 were produced in twenty -four hours. " Resting " conidia were 

 liberally formed. 



Boiled rice. — For the production of aerial mycelium no medium 

 except wheat meal was found to be better. The mycelium did not 

 produce irregularly branched or budding hyphse. At first only a 

 sterile growth was obtained, but about a month later a few sporangia 

 and many " resting " conidia were produced. When a sterile cul- 

 ture was incubated at about 18°C. a very poor crop of sporangia was 

 produced within a couple of days, possibly on account of the sudden 

 change of temperature. When a bit of the sterile mycelium was 

 transferred to water, sporangia were soon formed. 



Wheat meal. — This was prepared in the same way as maize corn 

 meal. It proved superior to boiled rice as it gave a more copious 

 aerial mycelium which readily produced sporangia in abundance. 



Bread paste ( + 10 Fuller* scale). — This medium was pre- 

 pared by mixing powdered stale bread with a sufficient amount of 



