Cytology of Pythium tdtimum , n. sp. 273 
abundant supplies of material could be obtained for demon- 
stration. 
The method adopted by me to secure material for investiga- 
tion was the well-known one of growing seedlings in the 
presence of excess of water, both in the soil and in the air. 
Garden soil was obtained from various sources in the neigh- 
bourhood of Cardiff and sowings of cress made in it in the 
usual way. The seed pans were kept in a closed cold frame, 
which was drenched with water twice a day. Most of the 
seedlings, as they came up, of course ‘ rotted off,’ and furnished 
the Pythium material. Somewhat to my surprise all the 
seedlings did not perish. It would be interesting to know 
the reason. The parasitic species of Fungus which presum- 
ably caused the death of the seedlings were very unsuitable 
for further examination. The mycelium was very delicate, 
and the reproductive organs were found either in small 
numbers or were conspicuously absent. Pythium de Baryanum 
was not seen. Some of the most suitable species were trans- 
ferred to Petri dishes and cultivated on fresh seedlings in 
abundance of water. The result was disappointing. No 
single suitable species was secured. 
In July, 1899, however, a very rotten cress-seedling, which 
was lying prone on the saturated soil, was taken for examina- 
tion. The stem was found on careful teasing to contain 
numerous spores. The spores were transferred to a cover- 
glass and a moist chamber culture set up, using for nutrient 
material a fragment of boiled cress cotyledon. Germination 
took place at once, and a good culture was obtained. This 
was transferred to a Petri dish and a larger culture made on 
two or three boiled cress-seedlings. Growth was luxuriant: 
in a few days a fine mycelium filled the dish and before the 
end of the week there were numerous sexual organs present 
and even ripe oospores. This culture furnished the material 
for all the subsequent ones. Further moist-chamber cultures 
were set up. using a single spore as the starting-point, and the 
life history was worked out in detail from the germination of 
the asexual spores (‘ conidia/ as we had better call them) 
T 
