Irish Societies, 



143 



IRISH SOCIETIES. 



DUBLIN MICROSCOPICAL CLUB. 



November 9. — The Club met at Leinster House. Paul A. Murphy 

 demonstrated tlie presence of a perennial mycelium in P.emnospora 

 Scheideni, Unger^ the Onion Mildew fungus. This fungus which causes 

 the well-known mildew of onions, is known to form its sexually-produced., 

 thick-walled resting spores in the leaves of its host. These spores find 

 their way into the soil with the decaying leaves, and it has always been 

 assumed that the re-appearance of the disease in spring is due to the 

 products of the germination of the resting spores. It has recently been 

 shown by the exhibitor [Nature, Nov. 3, 192 1, p. 304) that the parasite 

 can also hibernate in the vegetative condition, that is, as mycelium, in 

 onion bulbs. If such bulbs are planted and produce leaves, the latter 

 may be permeated from the beginning with the mildew fungus. The 

 internal parasite may show little or no sign of its presence until moist 

 weather ensues about May, when it suddenly appears in the form of the 

 well-known mildew all over the leaves. This method of hibernation has 

 been observed in all the commonly-grown forms of onion — the common 

 onion, the potato or underground onion and the shallot. The exhibit 

 consisted of (i) the mycelium of P. Schleideni in the bulb during the 

 winter period ; (2) the same mycelium as it grows up with the developing 

 leaf ; (3) the conidiophores and conidia, or summer spores, which this 

 mycelium produces in time on the surface of the leaves. 



H. A. Lafferty exhibited preparations of Thielavia basicola as 

 found growing naturally on Flax-roots in tl\e field. Affected plants, 

 when not killed outright in their seedling stage, remain small and 

 stunted in appearance. 



D. McArdle showed a rare liverwort, Blepharostoma tvichophylla in 

 fruit ; it is a remarkable plant, with the leaves divided to the base into 

 three or four segments, each segment hair-like, erect, composed of from 

 eight to twelve cells, stipules smaller than the leaves, tripartite. Perianth 

 ekserted white, composed of one layer of cells, mouth furnished with 

 three or four teeth-like cilia. Capsule cylindrical, spores small, reddish 

 brown, elaters long, narrow bispiral. This distinct species cannot be 

 confounded with any other British one. The specimens were collected in 

 Co. Kerry sparingly on decayed wood. It is also found in Co. Cork ; it 

 is rare in the north, as in Co. Galway, Co. Mayo, and on the east side at 

 Lough Bray, Co. Wicklow, always found in small quantities not common 

 in any known station ; found also on the Continent and in North America. 



BELFAST NATURALISTS' FIELD CLUB. 



October 26.-— The President (S. A. Bennett, B.A., B.Sc.) gave his 

 inaugural address, taking as his subject " The Comber Estuary," a district; 

 he said, which had been often visited by the club. The area is entirely 

 covered by glacial gravel deposited in late glacial times. This spreads out 



