117 



ALG^E. 



ALGJE. 



113 



with its reproductive granules arranged in fours. There are seven 

 British species of I' Ira : three growing in the sea, one in fresh water, 

 and three in damp places on the land. 



U. latissima, the Broad Green Laver, lias a plain, widely-oblong or 

 roundish frond, waved, arid of a green colour and tender substance. 

 It is an abundant plant on the rocks and stones of the sea in summer 

 and autumn. In common with U. Lacluca, the Lettuce Green Laver, 

 it is gathered and eaten in the same way as the Purple Laver. It is 

 also known under the name of Oyster Green. This plant is popularly 

 supposed to be good for scrofulous habits. It is sometimes applied to 

 the forehead to relieve headache in fevers, and also to procure sleep. 

 U. bttllosa, the Blistered Green Laver, is the fresh-water species. It 

 has an obovate, saccate frond, which is gelatinous, and at length 

 becomes irregularly expanded, waved, and bullate. It is a very fre- 

 quent plant in stagnant pools and ditches of fresh water, often covering 

 the whole surface of the water, and giving it the appearance of being 

 in a state of fermentation. Microscopically examined, this is an object 

 of no common beauty ; it seems as if composed of little green balls, 

 about as big as the blood-cells in the human blood, having no sort of 

 adhesion with each other, but holding together by a transparent thin 

 jelly. It is by these little green balls, or by the matter they contain, 

 that the Viva, is propagated. The common Laver of the shops very 

 nearly resembles it, but is a marine species. The terrestrial species 

 of Vita, are found growing on walls, rocks, the roofs of thatched houses, 

 and especially in places exposed to much moisture. U. thermalis grows 

 in hot-springs at a temperature of 117 Fahrenheit. 



The genus Tetrapora, named from the quaternary arrangement of 

 its granules, inhabits fresh water, and includes two British Species. 

 The fronds are tubular or inflated, and gelatinous. 



The Enteromorpha, Water-Gut, has a tubular, hollow, membra- 

 naceous frond, of a green colour and reticulated structure; the 

 reproductive granules are arranged in threes or fours in the reticu- 

 lations. Seven or eight species of this genus have been described as 

 British. They are all inhabitants of the sea, or of pools and ditches 

 of salt-water, with the exception of . intatinalw, which is also found 

 in fresh-water pools. All the species are long, varying from two or 

 three inches to three feet in length, and when floating in the water 

 very much resemble the intestines of an animal hence their name. 



Bangui was named after Hoffman Bang, a Danish naturalist, who 

 wrote a work on the Qtmfervae. It has a flat, capillary, membranaceous 

 frond, of a green, reddish, or purple colour. 



The order Otcillatariacea is composed of plants which are green or 

 brown in colour, with continuous tubular filaments, seldom branched, 

 though often joined together so as to appear branched. The fructifi- 

 cation consists of an internal mass divided by transverse septa, finally 

 separating into roundish or lenticular sporidia. This tribe of plants, 

 like the others, is found wherever there is water, and is more abundant 

 in fresh water than in the sea. There are however many of them 

 found in the sea, and also in mineral-waters. Many of the species, 

 especially of Otcillaiaria, are endowed with a power of moving so 

 apjiarently spontaneous, that some naturalists have placed them among 

 animals, as well as the more minute forms of plants belonging to the 

 order Alijtr. Captain Cannichael, who devoted much attention to this 

 subject, has made the following observations, which were published 

 from among his MSS, by Mr. Harvey : " I have been induced to 

 bestow considerable attention on such of the species as fell under my 

 notice, on account of the singular motion remarked in the filaments 

 by various naturalists ; and I do confess thad the result is something 

 like convietion that they belong rather to the animal than to the 

 vegetable kingdom. This motion or oscillation has been attributed 

 to various causes to the rapidity of growth, to the action of the 

 light, or to the agitation of the water in which the specimens were 

 immersed for inspection ; but none of these afford a satisfactory 

 explanation. The last may be put to the proof by a very simple con- 

 trivanc^. Let a small portion of the stratum be placed in a watch- 

 glass nearly filled with water, and covered with a circular film of talc, 

 so that its edge may touch the glass ; the water will be rendered as 

 fixed as if it was a piece of ice. The glass may now be placed under 

 the microscope, and the oscillation of the filaments viewed without 

 any risk of disturbance from the agitation of the water. By following 

 this course it will be speedily perceived that the motion in question 

 is entirely independent of that cause. The action of light as a cause 

 (if motion cannot be disproved, because we cannot view our specimens 

 in the dark ; but indirectly there is nothing easier. If a watch-glass 

 charged as above be laid aside for a night, it will be found that by 

 next morning not only a considerable radiation has taken place, but 

 that multitudes of the filaments have entirely escaped from the 

 stratum ; both indicating motion independent of light. Rapidity of 

 growth will show itself in a prolongation of the filaments, but will 

 not account for this oscillation to the right and left, and still less for 

 th-ir travelling in the course of a few hours to the distance of ten 

 their own length from the stratum. This last is a kind of motion 

 unexampled, I believe, in the vegetable kingdom. There is another 

 in the natural history of the Oicillatoriefr, which favours the 

 opinion that they are animalcules. It is the extremely limited term 

 of their existence. The community, if I may so call ifc, lives for several 

 months ; but the individuals die off, and are succeeded by others with 

 a rapidity to which there ie no parallel among genuine plants. If a 



.small portion of stratum, say one-fourth of an inch in diameter, be left 

 for three or four days in a watch-glass filled with water, the .whole 

 area of the glass will be found covered with a thin transparent pellicle 

 or incipient stratum, derived from the filaments that had successively 

 radiated and died in the course of that short period." 



There are several genera in the order Oicillatoriacece : Stiyonema 

 has cylindrical, cartilaginous, branched, inarticulate filaments, inclu- 

 ding granules ranged in transverse dotted rings. Scytoncma has 

 branched, flaccid, tough, continuous, tubular filaments, with brown 

 ^f olive-coloured endochrome, which is transversely striated, and at 

 length separates at the striae into lenticular sporidia. Calothrix has 

 erect tufted or fasciculate filaments destitute of a mucous layer, 

 fixed at the base, somewhat rigid, without oscillation. The tube is 

 continuous, and the endochrome is at length dissolved into lenticular 

 sporidia. Many of the species of Calotltrix are parasitical on other 

 plants. It is to this genus that the Conferva nivea of Dillwyn belongs. 

 It is the Calolhrix nivea of Agardh. This plant is remarkable for its 

 habitat in springs impregnated with sulphuretted hydrogen. It was 

 first found in the sulphur-springs of Croft in Yorkshire, by Dr. Willan, 

 and has since been found by other observers. Dr. Daubeny found it 

 .in many of the sulphur-springs of the Continent, and Dr. Lankester 

 collected specimens at Moffat, Harrowgate, Askern, and other places 

 where there were springs impregnated with sulphuretted hydrogen. 

 The decomposition of this plant, probably mixed with the remains of 

 other organic beings inhabiting the springs, has led to the supposition 

 that the springs in which it was found contained a pseudo-organic 

 matter which has been called by the names of Baregine, zoogeue, and 

 glairine. This was the opinion of the late Professor Anglada ; but 

 Dr. Lankester, having been able to form glairine by the decomposition 

 of the filaments of Calothrix nivea, renders it probable that there are 

 no compounds in mineral-waters, except the salts, which have not 

 been derived from plants or animalcules inhabiting the waters. 

 ('Annals of Nat. Hist,' 1841 ; ' Notice of Plants and Animals fouud 

 in Sulphureous Waters,' by E. Laukester, M.D.) The genus Lynybya 

 has free, flexible, elongated, continuous, decumbent filaments, destitute 

 of a mucous layer ; the endochrome densely aunulated, and separating 

 at the annuli into lenticular sporidia. This genus was named after 

 H. C. Lyngbye, a Danish botanist, and author of a work on the Alff<e 

 of Denmark. Some of the species are very common. The L. mm-alis 

 is found almost on every damp wall or walk, forming an intensely 

 green stratum of indefinite extent, which is very conspicuous after a 

 shower of rain. Other species are parasitic upon some of the fuci 

 and are found in the sea. 



The genus Oscillatm-ia has rigid, elastic, oscillating, simple, 

 continuous filaments, which are invested by a common mucous 

 matrix. The species are very numerous, but many of them are very 

 difficult to distinguish. They are not all found immersed in water, 

 but always occupy damp places. The 0. tenuissima is an inhabitant 

 of the warm springs of Bath, occupying broad velvet-like patches of a 

 dark green colour. Its singular appearance, Sir J. E. Smith observes, 

 " arises from the filaments being collected together into little ascending 

 tufts, apparently rooted in the muddy deposit of the water. Each 

 tuft proves, on examination, to consist of simple, reniform, even 

 filaments, crowded together, and quite pellucid and equally destitute 

 of joints and branches; their diameter. is not more than au 8-1000th 

 or 10-1 090th part of an inch." 



Oscillatoria distorta. a t natural size j ft, c, magnified. 



The order Noitocacece consists of plants with elliptical or globose cells 

 connected in gelatinous moniliform strings. The filaments are separate, 

 or several are united together in a gelatinous frond. The cells com- 

 posing the filaments are of two kinds ; first, a set of a bright green 

 colour, which constitute the greater part of the filaments, and 

 secondly, solitary cells of different form and size to the rest, destitute 

 of colour, and covered with cilia. They occur at intervals in all the 

 filaments, and are called 'connecting cells,' or ' heterocysts.' They 

 probably represent the antheridia in the higher plants. The 



