On the Cytology of Two Species of Characiopsis.

a collection of epiphytes was made from a -^ small stagnant rain-water pool in Pool Hollies Wood at Sutton Park, Warwickshire.The fallen leaves lying in the water were covered with a pale blue-green incrustation, which proved on examination to consist almost entirely of two species of Characiopsis Borzi, together with developmental stages of spores of Microthamnion and filamentous bacteria.One of the species of Characiopsis was identified as Ch.Ncegelii (A.Bi.)Lemm., but the other bas never previously been recorded, and is therefore described bere as a new species under the name of Ch. saccata.Since the material was available in considerable quantity a study of tbe cytology of the two species bas been made, and several interesting facts bave been revealed.Thus tbe great difference in tbe internal structure observed in tbese two species belonging to tbe same genus is ratber surprising, and not wbat one would have expected.This difference is obvious, even in tbe living condition, and although in the case of very young individuals tbe size and shape of the cell is often similar in botb species, there is no possibility of confusing tbem.Tbe larger species, Ch.Ncegelii, varied in size from 16-50/1 long and 6-28/ui broad, and the individuals were usually oval, elliptical, or sometimes suhspherical in shape, and except in tbe case of very young individuals tbe apex of tbe cell was always broadly rounded (Fig. 1, A-G).The smaller species reacbed in fairly large specimens a length of 82/A and a breadth of 15-16JLI, hut in this case there was very much more variation in the shape of the individuals (Fig. 2).Usually they were somewhat lanceolate, the apex being distinctly acuminate (Fig. 2, E, I, L, M andP).It not unfrequently happened, bowever, tbat distorted forms occurred, in wbicb the cells were rather irregular in outline, being very often more or less triangular (Fig. 2, A-D, F, G, H andJ). Tbese abnormal forms were very common amongst the smaller individuals, altbough occasionally some of tbe larger specimens also showed similar distortions.In botb species tbere is a very distinct, though sbort basal stalk, with a disc-like holdfast by means of wbich tbe organism is attached to tlie substratum.In the case of the triangular furnis, ' This idea is supported by Dr. E. Lemmermann in Algologjsche Beitrage.Xll, Die Gatiung Lharaciopsis Borzi, Abh.Nat.Ver.lirem.Bd.XXill, H. 1, 19H.Lemmermann only includes Characium horizontale A. Br.Ill Charcuiopsis as a doubtful species.