A13STIIACTS. 59 



Tkohoresco, E. C. — Materiaux pour la flore algologique tie la 

 Eoumanie. Bot. Centralb. Bd. xxi, Abt. ii. Heft 2. 



West, G. S. — 8oiue critical Green Algse. Journ. Linn. Soc, Bot. 

 xxxviii. (1908), pp. 279-289, tab. 20, 21. 



Bed lord College, 

 Kegeiit's Park. London, N.W. 1. 

 Nov. 1921. 



The Life-History ot" Stanrastrum Dicl'u'l var. parallelum (Nordst.). 

 By Charles Turner, E.C.S., Manchester. (Communicated 

 by the General Secretary.) 



[Read Gth April, 19i>2. 



(Plate 1.) 



The summer of 1921 was characterised by the long period of dry 

 weatlier during June and July ; the pastures were withered and 

 the grass beside the railways was burned in large patches. 

 Towards the end of the latter month I went to Glyn Ceiriog, a 

 picturesque district about four miles south of Llangollen. The 

 chief attraction is perhaps the little river Ceiriog, a tributary of 

 the Dee, which flows down tlie valley and is a stream well known 

 to the disciples of I/aac Walton for the excellence of the trout- 

 fishing and for the Eish Hatcheries near Chirk. When the rain- 

 fall is abundant the stream becomes a torrent, but the long 

 drought had caused its diminution, and the curi'eut had become 

 negligible in tlie detached pools which had been left at the side of 

 the stream. The district is in the Silurian formation, and tliere 

 are quarries of granite and slate as well as deposits of limestone 

 in the vicinity. I was looking out for Alg*, and had a small 

 microscope with me for the prcliminaiy e.xploration. After 

 a few days of introductory exploration, I settled down to 

 a semi-stagnant pool by the side of the river, not far from a 

 farm known to tourists as the place in wliich the chair of the 

 celebrated A\^elsh Bard, Hugh Morris, is still to he seen. One 

 of the slides which I have prepared has on it more than a hun- 

 dred zygospores of Staurastrum Diclclei \av. jjaraUeJum (Nord^iK), 

 in addition to those of two other Desmids, and the material has 

 yielded literally thousands of these in all stages of development. 

 I consider this to be largely due to the stagnation caused by the 

 drought. I had living material under observation for about three 

 weeks, and prepared many slides from it on the spot, in addition 

 to several dozen which 1 have subsequently obtained from pre- 

 served specimens. 



When I considered the great number of zygospores, I thought 

 I should be certain to find many conjugating individuals, and, 

 with that idea, I collected fresh material every day. AVhen 

 I returned home I found a large number showing the jdieno- 

 menon which 1 had previously failed to recognise. 



