The Scottish Naturalist. 185 



pora infestans originated, it was natural that it should be denied. 

 Accordingly, materials were put into the hands of Mr. George 

 Murray, by the Scientific Committee of the Royal Horticultural 

 Society, and that observer, taking to his assistance Dr. Flight of 

 the British Museum, tested the so-called sclerotiets, and declared 

 them to be merely masses of oxalate of time. 



Oxalate of lime is intimately associated with many minute fungi ; 

 some of the myxomycetes are covered with its crystals, as are also 

 some of the Pezizae. In the Peziza crucifera, every hair is sur- 

 mounted by a crystal of oxalate of lime. There is thus no impro- 

 bability in the assumption that the sclerotiet may be associated 

 with oxalate of lime. It has accordingly now been found, in op- 

 position to Mr. Murray and Dr. Flight that the body found in the 

 potato leaf, instead of being simply a mass of lime is in reality a 

 Plasmodium, coated with crystals of oxalate of lime. No one has 

 done more to demonstrate this point than Professor Trail ; but it 

 has been fully acquiesced in by Mr. Worthington G. Smith and Mr. 

 Greenwood Pim. Mr. Murray has replied that the oxalate of 

 lime instead of forming the coat, forms the core. From this 

 position also he has now, by the same observers, been completely 

 dislodged ; and the bodies are declared to be balls of some kind 

 of plasm, covered over with a coat of irregularly formed crystals. 

 These crystals are known to be the oxalate of lime because they 

 do not dissolve by application of acetic acid, as the carbonate of 

 lime does. They resist acetic acid but rapidly give way to nitric 

 acid. 



Such, briefly stated, is the present position on this point of struc- 

 ture ; but there is no proof thus far, that these " encrusted Plasm- 

 odia," are bodies having an arrested vitality like a sclerotium. 

 Observation of their germination can alone establish this conten- 

 tion. The present note cannot go into this department ; but may 

 conclude with a few hints to any one fascinated with the desire to 

 penetrate the mysteries of nature. The difficulty of course is to 

 see the lines of mycelium arising from the so-called sclerotiet. 

 The bodies cannot be seen at all in the leaves till they are macer- 

 ated for a few days in water and gently squeezed between two glass 

 slides. Then the lines of mycelium at their origin are so fine 

 that unless they are separated from the leaf tissue they cannot be 

 seen at all ; a sufficient power cannot get within focus of them. 

 The best method yet hit upon is to strip the cuticle from the lower 



