TRANSACTIONS OF SECTION K. 941 



tive solubility in water and in a mixture of cholesterin and lecithin. A know- 

 ledge of the osmotic properties of the living protoplasm throws much light on the 

 action of many poisons and other drugs. 



4. The Biology and Cytology of a New Species of Pythium, 

 By Professor A. H. Trow. 



1. The reproductive organs of this fungus, ' conidia ' and oospores, were found 

 in rotten cress seedlings in July 1899, and the species has been cultivated as a 

 saprophyte on sterilised potatoes, house-flies, cabbage leaves, &c., up to the 

 present time (September 1900). 



2. The species appears to be a pure saprophyte, all attempts to infect fresh 

 cress seedlings having hitherto failed. 



•3. Pure cultures were obtained by infecting sterilised potatoes with materials 

 obtained from cultures on rhubarb leaves. 



4. On potatoes an aerial mycelium is freely developed, which remains sterile 

 for weeks. Conidia and oospores ultimately develop in numbers, their presence 

 being readily recognised by their yellow colour. 



5. On house-flies or bits of cabbage leaves immersed in water the mycelium is 

 aquatic, and, as a rule, that developed on house-flies produces conidia, that on 

 cabbage leaves oospores. 



6. The life history has been carefully followed under the microscope in moist- 

 chamber cultures. It is noteworthy — 



(a) That De Bary erred in including the greater portion of the periplasm in 

 the oosphere. 



(6) That there is no sharp line of differentiation between periplasm and 

 gonoplasm in the antheridium. 



(c) That most of the periplasm is absorbed by the young oospore, which in 

 consequence increases in size. 



{d) That the conidia and oospores on germination invariably produce germ 

 tubes, no zoospores being formed under any circumstances. 



(e) That the conidia germinate at once in a decoction of cabbage leaves, but 

 remain at rest in distilled water ; that the oospores germinate at once, as soon as 

 ripe, or after a rest of as much as seven months. 



7. The species is consequently new and rants as the most highly developed of 

 the genus. 



8. The mycelium ' conidia,' oogonia, and antheridia are multinucleate, the 

 oosphere is uninucleate, the young oospore binucleate, and the ripe oospore uninu- 

 cleate. 



9. The nuclei multiply by indirect division in the mycelium and sexual organs. 

 No nuclear changes of importance take place in the ' conidia.' The only nuclear 

 fusion is that of the male and female nuclei in fertilisation. The number of 

 chromosomes is considerable, certainly more than six. 



10. The oogonium, as it is formed, receives fifteen or more nuclei, the 

 antheridium three or more. These invariably divide once, so that the number of 

 nuclei is doubled. The supernumerary nuclei in the oogonium lie in the periplasm, 

 the female nucleus passes to and occupies the centre of the oosphere. No similar 

 distribution of the nuclei takes place in the antheridium. 



11. The fertilisation tube penetrates the wall of the oogonium at a spot pre- 

 pared for it, passes through the periplasm, and penetrates deeply into the ecrg. 

 One male nucleus passes down the tube and enters the egg. The oosphere clothes 

 itself with a delicate cell-wall and increases in size. 



12. The fusion of the male and female nuclei is delayed until a thick oospore 

 wall has developed. No epispore is formed. 



13. The fate of the nucleus in the germinating oospore has not vet been 

 followed. In the conidia nuclear divisions occur as germination proceeds" 



