520 



♦ KNOWLEDGE • 



[Dec. 26, 1884. 



United States. After entering on political life in America, 

 a man's best chance of becoming rich lies in the judicious 

 application of his political iniluenca to furthering, at a 

 price, Buch finauoial schemes as come in his way. Politi- 

 cians in America see nothing wrong in this employment of 

 their influence. I have no douVjt Mr. Blaine was quite in 

 earne.st in saying that he had no reason to be ashamed of 

 anything which came out respecting his correspondence with 

 Mr. Fisher, though an English statesman (if one could con- 

 ceive anything of the kind happening in England) could 

 never have raised his head again after such a disclosure. 

 Nor do most other American politicians appear to have 

 been much surprised or ashamed at anything which 

 appeared in those Mulligan letters. 



It seems tolerably manifest that we can make no com- 

 parison between American and English morality in matters 

 political, until we have an opportunity of observing how 

 matters proceed when the best classes in America take to 

 politics, and thrust to their deserved position in the back- 

 ground the adventurers who now disgrace the nation. It 

 may well be that then the gambling sjiirit will be found to 

 be no more widely prevalent in America than in oiir own 

 country. At present, it unquestionably is much more 

 obtrusive. — Newcastle Weekly Chronicle. 



AN INTERESTING FAMILY. 



By David Houston, F.L.S. 



NOT at all uncommonly in the still, clear water of open 

 drains or sheltered ditches may be found a floating, 

 elongated, ragged, or sac-like net of green, buoyed one end 

 uppermost by a mesh-entangled bubble of gas evolved by 

 the living moieties of the singularly complex organism. 

 The net, as will be readily observed, varies considerably in 

 size ; but three or four inches long and one to one and 

 a-half inches deep may be taken as a typical full-growth 

 measurement. 



-" Water-Net 



(HydroJic'yon), natural size. 

 Cooke. 



This peculiar vegetable growth (Fig. 1) is an algal family 

 of very many individuals, each individual simply consisting 

 of an elongated or oblong cylindrical rod (Fig. 2) about a 



Fig. 2.- A tiiigle cell or imiividual (very mucli enlai-ged) from the 

 Water-net colony. 



line or so in length, brightened in the season of active 

 growth with a light or vivid green colour. Structurally, 

 each rod is made up of a mass of protoplasm enclosed in 

 an exceedingly thin cellulose wall forming a single histo- 

 logical element or cell. The green pigment or chlorophyll 

 is confined to the protoplasm, and to that part of the 



protoplasm that lies immediately within the cell-wall, 

 leaving a slender, colourless portion in the central region 

 of the tiny plant. 



Instead of living a life of comparative isolation, like a 

 great many unicellular and other simple alg.-e, these inte- 

 resting organisms elect to form special groups, or families, 

 and share together the seasonal ups and downs of quiet 

 vegetable life in the drainage-water of an unpolluted ditch. 

 In the formation of a colony, either end of any individual 

 cell meets one of the ends of each of two other cells, and, 

 as a geometrical result, meshes averaging about one-sixth 

 of an inch are constructed, each space being bounded by 



Fig. 3. — One of the " Meshea " of Water-Net (magnified). 



Cohn. 



After 



five cells (Fig. 3). The presence of a gelatinous substance 

 adhering to the outside of the cell walls — and, perhaps, 

 arising from a slow disintegration of the material of the 

 wall itself — is of very common occurrence among members 

 of the class of alga'. It is by virtue of the existence of this 

 jelly-like matter that the individuals of this family can 

 remain closely, although not organically, attached, and form 

 a net-like floating communitv, or sisterhood. 



The plant, or rather the assemblage of plants, is known 

 " vulgarly " as the " water-net," while its scientific, generic 

 name of Hydrodictyon (Gr., hudor, water ; diktuoii, a 

 fishing-net) expresses exactly the same idea as tSe common 

 or simple one. There is — so far as is at present h.^own — 

 only one species of Hydrodictyon (lf>jdrodict>jon lUricu- 

 lalum). It is distributed throughout the pure fresh waters 

 of Europe and North America, never, it seems, attaining 

 in any locality a size beyond a length of twelve inches, with 

 meshes of a third of an inch in diameter. Like all chloro- 

 phyll-bearing plants, the water-net is able to manufacture 

 starch under the influence of solar light and heat out of the 

 chemical elements of carbonic acid gas and water ; but, as 

 there is more oxygen proportionately present in the dioxide 

 of carbon and monoxide of hydrogen than in the molecules 

 of starch, a considerable quantity of pure oxygen is liberated 

 during the hours of sunshine, and it is from this source 

 that the gaseous body above referred to is kept in existence 

 day by day throughout the plant's active period of vegeta- 

 tive growth. The manufactured starch may be discovered 

 in the form of minute grains lying in the peripheral or 

 greenish region of the protoplasm ; but their presence can 

 be rendered clearly visible by treatment with solution of 

 iodine, under the action of which the grains will assume 

 a dark blue colouration. It is, of course, from this starch 

 and from protinaceous substances formed through the vital 

 activity of the plant, together with certain ever-essential 

 inorganic salts obtained from the drainage water, that the 

 protoplasm derives its constructive material or food, and 

 out of which it is able to build up new protoplasmic sub- 

 stance, enabling it to increase itself in size, and, in due 

 time, to attain an adult condition. 



After a course of purely vegetative growth, during 

 which all the energies of the plant are directed to its 



