158 



SCIENCE-GOSSIP. 



GREEN SCUM ON WATER. 



By James Burton. 



TN July, the surface of the water of the 

 ■'• Military Canal at Hythe, was covered with 

 numerous patches, of varying size, of a pale 

 yellowish green slime. I expected they would 

 prove to be composed of one of the many different 

 forms of Euglena which are so common, often 

 giving a green colour to water and collecting on 

 the surface. On bringing some home for examina- 

 tion, the patches were found to consist almost 

 entirely of one of the Nostochacese. The nomen- 

 clature of this order is uncertain, and the 

 determination of the genera by no means easy, 

 partly owing to the number of naturalists who 

 have attempted its arrangement. My specimens 

 consisted of short, nearly straight filaments of 

 minute globular cells, somewhat flattened where 

 joined to their neighbours, of a pale yellowish 

 green, filled with granular protoplasm, many of 

 them more or less constricted in the middle, 

 showing they were undergoing division. At 

 intervals, a cell with clear contents and decided 

 spherical form occurs, these are called heterocysts, 

 but their function does not appear to be known. 

 Occasionally also a much larger cell is found, 

 ovate in shape, and filled with densely granular 

 protoplasm, these are sporangia and contain each 

 one spore at maturity, enclosed in a second wall. 

 The whole resembled very closely the common 

 nostoc, the chief differences being that in nostoc 

 the sporangia, so far as I am aware, are absent, and 

 the filaments are enclosed in a mass of jelly-like 

 substance, which here was almost if not entirely 

 wanting. The fact that the heterocysts and 

 sporangia occurred at intervals, separated by 

 ordinary cells, while the sporangia were not greatly 

 elongated, would indicate that the specimens 

 belonged to the genus Anabcena (see under heading 

 " Trichormus " in third edition " Micrographic 

 Dictionary"). The plants lived very well for 

 several days in a collecting-bottle, apparently with- 

 out any change taking place, but when transferred 

 to a small aquarium, in which it was hoped they 

 would flourish, the mass at once broke up and the 

 organisms were diffused through the water and 

 perished. This was the more regrettable as a 

 careful examination had not been made, and it was 

 necessary to fall back on a mounted specimen for 

 identification and description. This has conse- 

 quently been rather doubtful, as a certain amount 

 of alteration may have taken place in the process. 

 Very likely the water of the canal is brackish or 

 even salt, and the fresh water proved fatal to the 

 plants. Among the Anabcena there were also 

 numbers of small-lobed masses of jelly with minute 



green separate cells embedded in them, closely 

 resembling the figure of Chloroccum frustulosum in 

 Dr. Cook's "British Freshwater Algae," but I 

 have not the text of the book at hand for reference 

 as to habitat, etc. There were present a few of the 

 ubiquitous spindle-shaped £2<o'/£'«fl with red "eye- 

 spot " at one end and clear pointed tail at the 

 other. 



Since writing the above I have come across 

 another example of the order. This was on the 

 surface of the earth, in a large flower-pot under 

 a bell - glass, and the characters being more 

 definite than in the other case, identification 

 as Cylindrospermiun was easy and certain. The 

 gelatinous matrix, instead of being in lumps, 

 or more or less globular masses, as is the case 

 with Nostoc commune, is spread in a thickish layer 

 on the substratum, so that the whole is much less 

 noticeable. The general colour is dark green, but 

 brighter than in N. commune. The plant consists 

 of somewhat short beaded strings. The ordinary 

 cells are globular, slightly flattened where joined 

 to their neighbours, and filled with granular 

 protoplasm. The heterocysts and sporangia are 

 very characteristic ; the former are terminal, 

 globular, protoplasm clear pale green and fringed 

 with hairs, sometimes longer than the breadth of 

 the cell ; the sporangia are cylindrical with 

 rounded ends and densely granular contents, 

 and occur next the heterocysts, i.e. they are 

 penultimate. The position and form of these 

 cells indicate Cylindyospermiim. According to 

 the " Micrographic Dictionary," the plant is 

 "distinguished under the microscope by the resem- 

 blance of the filaments to an annulose animal, the 

 ordinary cells looking like a jointed body, the 

 large elliptic sporangial cell like a thorax, and the 

 terminal vesicular cell often bearing fine hairs, like 

 a head." At any rate it is an interesting and 

 distinct form. 



Owing to the wet autumn, lower algae of many 

 species are extremely common now, every footpath, 

 the bases of walls and trees swarm with them ; 

 all are well worth and easy of examination, but 

 identification is often difiicult. Dark blue-green 

 Oscillatoriece show like a black stain, and various 

 Palmellacece almost like a patch of blood. A 

 common form is very similar to, if not identical 

 with, that causing "red snow" so often invested 

 with a gleam of sentiment in accounts of Alpine 

 travel. I shall be pleased to forward a small 

 specimen of Cylindrospermum to anyone caring to 

 enclose address and stamp for postage. 



9, Agamemnon Road, West Hampstead, London. 



