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SIR DAVID SALOMONS BART.
BROOMHILL ,
TUNBRIDCE WELLS.
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BOOK 589.61. R13 c. 1 RALFS # BRITISH DESMIOIEAE
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3998 RALFS (J.) The British Desmidie^. Drawings by o
Edward Jenner. Reeve, London. 1848. Broivn calf, gilt top. 81^0. i vol. Cover inserted.
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BRITISH DESMIDIE.F..
» Jl^
THE
BRITISH DESMIDIEtE.
JOHN RALFS, M.R.C.S.,
HONORARY MEMBER OF THE PENZANCE NATURAL HISTORY SOCIETY, ETC.
THE
DRAWINGS
EDWARD JENNER, A.L.S.
LONDON: REEVE, BENHAM, AND REEVE,
KING WILLIAM STREET, STRAND.
1848.
PRINTED BY RICHARD AND JOHN E. TAYLOR, RED J.ION COURT, FLEET STREET.
TO
WILLIAM BORRER, ESQ.,
F.R.S., L.S. &c.
DEAR SIR,
As your suggestion induced me to study the Microscopic Alga with greater diligence, and as I have been mainly indebted to your assistance and encouragement for the successful completion of the present Monograph, I feel it a grateful duty to dedicate to you the collected fruits of my investigations, and, sincerely thanking you for the kind permission to associate them with a name so honourably distinguished in Botanical Science^
fv, I am, dear Sir,
it^ ^
\
Your truly obliged,
JOHN RALFS.
PREFACE.
Although this work has greatly exceeded the limits which I originally contemplated, I am very far from thinking that it has exhausted the subject. About one-third of the Des- midiese which it describes have been discovered in this country since the prospectus was issued ; a fact which may well warrant the expectation that a rich harvest yet remains to reward the dihgence of future labourers. In regard also to the reproductive organs; whilst I have the pleasure of noticing that the sporangia of fifty species are here^figured, most of them for the first time, I would point out that those of a much larger number are still unknown, and that every spring and summer many are brought to light.
In compliance with the request of some of my Subscribers, I have added a few foreign habitats, w^iich will give some idea of the geographical distribution of the species. This I am enabled to do through the kindness of M. de Brebisson and Professor Bailey, who have furnished me with complete lists of the species found by them. It must of course be considered merely the first rude chart of their range, and I earnestly deprecate any comparison of it with what Professor Harvey has accomplished for the Marine Algee in his splen- did ' Phycologia Britannica' : nevertheless enough is here exhibited to show the cosmopolite character of these plants, since not only has almost every British species been found at
VI PREFACE.
Falaise by M. de Brebisson, but most of them have also American habitats.
It has been mj' desire throughout to write impartially, and I am not aware that I have, in a single instance, neglected the claim of priority, or appropriated to myself the disco- veries of others. Should any blemishes of this kind appear, they will, I trust, be attributed to the circumstance that this work has been composed at a distance from the metropolis, and without access to many works which it would have been desirable to consult. Amongst these I have more especially to regret that I have not seen some valuable papers on the Desmidiese by Ehrenberg, Corda, and Morren, which have been published in various foreign periodicals.
In these pages the name appended to a species merely in- dicates the author of the specific name, and has no reference to its genus. This departure from the usual custom seems to me to require no vindication ; for it is surely unjust that the credit due to the discoverer or first describer of a plant should be ascribed to one whose sole merit in regard to it has been to transfer it from one genus to another. To those who prefer the common method, the synonyms will afford the requisite information.
I consider Merismopedia and Trochiscia to belong to the Palmelleae, and have therefore omitted them, although Kiit- zing and Meneghini include them in this family. I am also unacquainted with any species of Sphcerastrum which can rank with the Desmidiese.
Penium Digitus, and, except in a few cases which are pointed out, the species of Closterium, Docidium and Micrasterias, are, on account of their comparatively large size, magnified only 200 diameters, but all the others are magnified 400 diameters.
PREFACE. vil
Mr. Jeniier and myself have used Mr. Ross's microscopes, and I think it due to that skilful optician to state, that for clearness of vision we have never seen them surpassed.
I have added, as an Appendix, a list of as many foreign species as have come to my knowledge ; and, although I fear that a few of Ehrenberg's may have been omitted, I have some confidence that this work describes and figures a greater number of species than have before been systematically arranged. M. de Brebisson and Professor Bailey have kindly permitted me to insert species which they have recently de- tected, and which are now first published, and also to make use of their drawings. The last plate has been reserved for these drawings and for others which Professor Kiitzing has presented me of species which he has described but not figured. I have to regret that the large size of the Closteria did not allow the introduction of figures of several interesting foreign species.
The drawings of the British species, with very few ex- ceptions, were made by Mr. Jenner ; but they have, in almost every instance, been carefully re-examined by myself and compared with the plants, and the engravings have been executed under my own superintendence. From the com- mencement of this undertaking Mr. Jenner's help has been invaluable. Not only has he taken the greatest pains to ensure the accuracy of the drawings and furnished me with copious notes, but to his exertions I owe a very large pro- portion of my Subscribers. Indeed I can truly say that he has shown as great an interest in the work as if it were his own, and exerted himself as much for me as he would have done for himself.
To the kind recommendations of Mr. Bowerbank, who is
viii PREFACE.
as distinguished for his indefatigable and successful micro- scopic observations as for his constant readiness to encourage his fellow-labourers in Natural History, I owe the patronage of many of the eminent naturalists whose names adorn the list of my Subscribers ; and, to render this Monograph more complete and deserving of such support, he has taken the trouble of measuring all the species. Tedious and uninviting as the task must have been, these accurate measurements will show how much his love of science has contributed to enrich a work of which I regard them as one of the most important features.
It gives me sincere pleasure to acknowledge how much I am indebted to the kindness of M. de Brebisson, who has so long studied these Algae, and who is deservedly esteemed the highest authority on the subject. By his valuable aid my nomenclature has been rendered far more perfect than it could otherwise have been. He has most liberally supplied me with specimens and drawings of almost every species ; has copied, for my use, figures contained in works which I had no opportunity of consulting, and has at all times readily furnished me with such information as I required. To the extent indeed of my obligations in these respects every page of this work bears frequent but inadequate testimony.
Professors Kiitzing and Bailey have also afforded me important assistance, by supplying me with drawings of many species and by the communication of interesting facts.
My friends, the Rev. M. J. Berkeley, Dr. Dickie, Mr. Sidebotham, and Mr. Thwaites, have materially aided me in the execution of this Monograph by sending me their obser- vations and specimens. Dr. Williams of Swansea has obli-
PREFACE. IX
gingly furnished me with copious translations from German works.
To no one are my obhgations greater than to Mr. Borrer : by his advice and assistance the work has been freed from many defects that would have impaired the utility which I trust it may now possess. I gladly return my thanks also to my valued friend the Rev. H. Penneck, who has afforded me his assistance throughout its progress and in its careful preparation for the press.
My thanks are due likewise to many other friends, for the interest which they have taken in this publication, and for their exertions to secure me from pecuniary risk ; especially to Mrs. Griffiths, Miss Warren, Professor AUman, Mr. An- drews, Professor Balfour, Mr. Coates, Mr. R. Q. Couch, Mr. Dillwyn, Mr. P. Grant, Dr. Greville, Mr. Gutch, Mr. W. Hanson, Professor Harvey, Rev. D. Landsborough, Mr. Mog- gridge, Mr. Moore, Dr. Shapter, Mr. W. Thompson, Mr. Topping, Mr. Tudor, and Mr. Williamson.
I have to apologize for the long delay in publishing. It has been caused partly by ill health, but chiefly by the con- tinual discovery of additional matter and my wish that no labours on my part should be wanting. When however I state that I have thus been enabled to add the descriptions of a large proportion of the species and of one-half of the sporangia, besides the Appendix of foreign species, and at least ten plates, I may be permitted to hope that the Sub- scribers will readily excuse a delay which has so materially increased the extent of the work without increasing its price.
SUBSCRIBERS.
Royal College of Surgeons of England.
Ro3'al Dublin Society.
Royal Society of Edinburgh.
University and King's College, Aberdeen.
Royal Geological Society of Cornwall.
Botanical Society of Edinburgh.
Microscopical Society of London.
Microscopical Society of Dublin.
Microscopical Society of Bristol.
Belfast Library.
Trinity College Library, Dublin.
Devon and Exeter Botanical and Horticultural Society.
Devon and Exeter Institution,
Royal Horticultural Society, Cornwall.
University Library, Edinburgh.
"Wernerian Natural History Society of Edinburgh.
Adam, Thomas, Esq., Halifax.
AUcard, John, Esq., F.L.S., &c., 65, Lombard Street, London.
Allingham, Mr. "William, Reigate.
Allman, G. J., M.B., M.R.I.A., F.R.C.S.I., M.B.S.E., &c.. Professor of Botany in Trmity College, Dublin.
Anderson, T. P., Esq., M.R.I., 45, Harewood Square, London.
Andrews, W., Esq., M.R.I. A., B.S.L., Secretary to the Natural History So- ciety of Dublin. 2 cojjies.
Ansted, D. T., Esq., M.A., F.R.S., Professor of Geology, King's College, London.
Aruott, George A. Walker, Esq., LL.D., F.R.S.E., F.L.S., Regius Professor of Botany, Glasgow.
Ayerst, Mr. Thomas, jun.. Hill Cottage, Newenden, Kent.
Babington, C. C, Esq., M.A., F.L.S., G.S.,&c., St. John's College, Cambridge.
Babington, Churchill, Esq., B.A., Fellow of St. John's College, Cambridge.
Bagster, George, Esq., Paternoster Row.
Baillie, Mrs., Hill Park, Westerham, Kent.
Balfour, J. Hutton, M.D., F.R.S.E., L.S., &c., Regius Professor of Botany, Edinburgh.
Ball, Robert, Esq., M.R.I.A., B.S.E., Vice-President of the Geological Society of Dublin.
xii SUBSCRIBERS.
Bardsley, James L., M.D., F.L.S., Manchester.
Barrow, R., Esq., M.R.C.S., Manchester.
Bass, Mrs., Brighton.
Bayne, A., Esq., Tunbridge Wells.
Beaufort, Rev. D. A., 11, Gloucester Place, Portman Square.
Beck, Mr., Coleman Street, City.
Bell, Frederick J., Esq., Woodlands, near Maldon, Essex.
Bell, Robert J., Esq., M.R.C.S., Mickleover House, near Derby.
Bell, Thomas, Esq., F.R.S., L.S., G.S., &c., Professor of Zoology, King's College, London.
Bennett, W., Esq., 7, Park Village West, Regent's Park.
Bentley, Robert, Esq., King's College, London.
Bergin, Thomas F., Esq., M.R.I.A., President of the Microscopical Society of Dublin.
Berkeley, Rev. M. J., M.A., F.L.S., King's Cliffe. 3 copies.
Bird, Golding, M.D., M.A., F.R.S., F.L.S., Lecturer on Botany, Guy's Ho- spital, &c., Myddelton Square, London.
Birkby, Henry, Esq., Rochdale.
Birkett, John, Esq., F.L.S., 2, Broad Street Buildings.
Bladon, James, Esq., Pont-y-Pool, Monmouthshire.
Bond, Mr., Richards Buildings, Hackney Road.
Borrer, W., Esq., F.R.S., L.S., M.B.S.E., &c., Henfield. 2 copies.
Bowerbank, J. S., Esq., F.R.S., L.S., G.S., &c., Highbury Grove, London.
Boyle, W. A., Esq., F.L.S., 37, Granville Square, Pentonville.
Braikenridge, G. W., Esq., F.S.A. & G.S., Broomwell House, Brislington, near Bristol.
Briggs, Mr. Charles, Brighton.
Bright, Richard, M.D., F.R.S., Saville Row, London.
Brightwell, Thomas, Esq., F.L.S., Norwich.
Brittain, Thomas, Esq., Manchester.
Broome, C. E., Esq., M.A., M.B.S.L., B.S.E., &c., Clifton.
Broomfield, Wilham Arnold, M.D., F.L.S., Ryde, Isle of Wight.
Brown, Edwin, Esq., Burton-on-Trent.
Brown, H., Esq., Lewes.
Brown, Isaac, Esq., M.B.S.E., Dorking.
Brown, Robert, Esq., D.C.L., F.R.S., V.P.L.S., &c,, British Museum.
Browne, Henry, M.D., M.R.C.S., Manchester.
Buckland, The Very Rev. W., D.D., Dean of Westminster, F.R.S., G.S., F.L.S., &c.. Professor of Geology and Mineralogy, Oxford.
BufPham, Mr. William, Rochdale.
Bunting, Frederick, Esq., Westhall Place, Cheltenham.
Busk, George, Esq., F.L.S., F.R.C.S., Groom's Hill, Greenwich.
Button, Charles, Esq., M.M.S.L., Holborn.
Callwell, Robert, Esq., M.R.I.A., Dublin. Capron, J. R., Esq., Guildford. Carey, J., Esq., Strand, London.
SUBSCRIBERS. XIU
Carpenter, W. B., INI.D., F.R.S., 6, Regent's Park Terrace, Gloucester Gate.
Carpenter and Westley, 24, Regent Street, London.
Casey, J., Esq., Lea Bridge Road, London.
Cattell, ]\Ir. J., Westerham, Kent.
Clark, Rev. W., M.D., F.R.S., Professor of Anatomy, Cambridge.
Clark, Edwin, Esq., George Street, Westminster.
Coates, John, Esq., M.R.C.S., &c,, Rochdale.
Coathupe, Ch. Thornton, Esq., Wraxall, Bristol.
Cobb, Rev. S. W., Ightham, Kent.
Colbran, Mr. J., Tunbridge Wells.
Collins, Henry, Esq., Berkeley Lodge, Chichester.
Combe, Miss M. A., Cobham Park, Surrey.
Cook, George, Esq., Manchester.
Couch, R. Q., Esq., M.R.C.S., M.R.C.G.S., &c., Penzance.
CuUen, W. H., M.D., Sidmouth.
Curme, George, Esq., M.R.C.S,, Dorchester.
Currer, INIiss Richardson, Eshton Hall, Gargrave, Yorkshire. 2 copies.
Cutler, Miss, Budleigh Salterton, Devonshire.
Dalrymple, J., Esq., T.R.C.S., Grosvenor Street, London.
Daly, Rev. W. J., M.A., O.M.I., Penzance.
Dancer, J. B., Esq., Manchester.
Darby, Alfred, Esq., Coalbi'ook-dale.
Darker, W. Hill, Esq., Paradise Street, Lambeth.
Daubeny, Charles G. B., M.D., F.R.S., L.S. and G.S., Hon. M.R.LA., Regius Professor of Botany, Chemistry, and Rural Economy, Oxford.
Davis, Mr. John, Mile-end Road, London.
Davis, Richard, Esq., F.L.S., H.S., and R.B.S., 9, St. Helen's Place.
Deane, H., Esq., Clapham Common.
Death, Mr. W., Petworth.
De Boos, E., Esq., Elder Street, London.
De la Rue, Warren, Esq., Bmahill Row, London.
De Ruvignes, C. H., Esq., Cape of Good Hope.
Diamond, Mr. A. G., Brenchley, Kent.
Diamond, Hugh W., Esq., Frith Street, Soho.
Dickenson, Henry, Esq., Coalbrook-dale.
Dickie, G., M.D., M.B.S.E., Lecturer on Botany, Aberdeen.
Dickinson, J., Esq., M.A., M.D., F.L.S., &c.. Lecturer on Botany, Liverpool.
DillwjTi, L. W., Esq., F.R.S., L.S., &c., Sketty Hall, Swansea. 2 copies.
Donald, Ernest, Esq., Aberdeen.
Doxat, Alexis James, Esq., Putney Heath.
Drummond, J. L., M.D., Professor of Anatomy and Physiology, Royal Bel- fast Institution.
Durrant, Richard, Esq., London.
Elliott, W. H., M.D., F.L.S., M.R.C.S., &c., Boverie House, Mount Radford, Exeter.
Elsey, J. R., Esq., Lonsdale Square, Islington.
xiv SUBSCRIBERS.
Estlin, J. B., Esq., F.L.S., F.R.C.S., Bristol.
Etheridge, Mr., Cheltenham.
Ferris, Octavius Allen, Esq., Victoria Park, Manchester.
Fielding, H. B., Esq., F.L.S., Bolton Lodge, Lancaster.
Foord, George, Esq., Walter Street, Soho. 2 copies.
Foot, Simon, Esq., M.R.I.A., B.S.E., &c.. Holly Park, Dublin.
Forbes, Edward, Esq., F.R.S., L.S., G.S., &c.. Professor of Botany, King's College, London.
Ford, John William, Esq., 9, Duke Street, London Bridge.
Forster, Edward, Esq., F.R.S., Treas. & V.P.L.S., &c., Woodford.
Freeman, J. D., Esq., Plymouth.
Fry, P. W., Esq., Montague Street, Russell Square.
Gamwell, F., Esq., Myddelton Terrace, Islington.
Gillett, W. S., Esq., Wilton Street, Grosvenor Place.
Godley, Mr, William, Wallingford, Berks.
Goodsir, J., Esq., F.R.S., Professor of Anatomy, University, Edinburgh.
Gordon, P. S., Esq., Craigmyle.
Gorham, J., Esq., M.R.C.S., Tunbridge.
Graham, R., Esq., Buxton House, Walthamstow.
Grant, J. W., Esq., Calcutta.
Gratton, Joseph, Esq., 94, Shoreditch, London.
Graves, Mr, George, Hackney.
Gray, T., Esq., Manchester.
Gray, John, Esq., Greenock.
Greenwood, Alfred, Esq., M.B.S.E., Chelmsford.
Greville, R. K., LL.D., F.R.S.E., &c., Edinburgh.
Griffith, Mrs., Torquay.
Grindon, L. H., Esq., Manchester.
Grosvenor, Rt. Hon. Lord Robert, M.P., 107, Park Street, Grosvenor Square.
Gutch, J. W. G., Esq., M.R.C.S., B.S.L., &c.. Great Portland Street.
Gwilt, George, Esq., Union Street, Borough.
Hair, Quintin, B., Esq., 288, Regent Street, London.
Hamilton, Edward, M.D., F.L.S., &c., 22, Grafton Street, Bond Street.
Hankey, J. A., Esq., F.L.S., 8, Grosvenor Square, London.
Hanson, Mr. William, A.L.S., Reigate.
Harvey, W. H., M.D., M.R.I.A., Professor of Botany to the Royal Dublin Society, Trinity College, Dublin. 2 copies.
Hatch, Mr. Benjamin, Tenterden.
Heddle, Robert, Esq., Orkney.
Henfrey, A., Esq., F.L.S., Lecturer on Botany, Middlesex Hospital, 6, Shrews- bury Cottages, Holland Road, North Brixton.
Henslow, Rev. J. S., M.A., F.L.S., G.S., C.P.S., Professor of Botany, Cam- bridge, and Examiner in Botany in the University of London.
Heryer, Jacob, Esq., Great St. Helens, Bishopgate Street.
Hetling, George, Esq., Bristol.
Heyworth, Rev. J., Henbury Hill, near Bristol.
Holmes, George B., Esq., Horsham, Sussex.
SUBSCRIBERS. XV
Hooker, Joseph Daltou, M.D., F.L.S., Mem. Imp. Acad. Cses. Leop. Nat.
Curiosorum, &c. Hooker, Sir W. J., K.H., LL.D., F.R.S., V.P.L.S., &c., Kew. Hore, Rev. W. S., M.A., F.L.S. and G.S., Stoke, Devonport. Howard, D., Esq., 22, Beriiers Street, Oxford Street. Howman, J. A. Knightly, Esq., Brompton Square. Hurst, Z. D., Esq., F.G.S., Aylesbury. Ingpen, Abel, Esq., A.L.S., King's Road, Chelsea. Inkson, Mr. William, Chichester. Irving, General, Solway, Kirkcudbright. Jackson, John, Esq., Hackney. Jackson, Rev. W., Fellow of Worcester College, Oxford, and Incumbent of
All-Saints, Sidmouth. Janson, Henry U., Esq., Pennsylvania, Exeter. Janson, J., Esq., F.L.S., Stoke Newington. Jenyns, Rev. Leonard, M.A., F.L.S., G.S., and C.P.S., Swaffham Bulbeck,
Newmarket. Johnson, Christopher, jun., Esq., M.R.C.S., Lancaster. Johnston, G., M.D., LL.D., F.R.C.S.E., Berwick-upon-Tweed. Jones, S. M., Esq., Sloane Street, Chelsea. Jones, Capt. Theobald, Royal Navy, M.P., F.L.S., G.S., &c., 30, Charles
Street, St. James's. 2 copies. Josephs, Walter, Esq., 15, Crown Street, Finsbury, London. Just, J., Esq., M.B.S.E., Grammar School, Bury, Lancashire. Keddie, W., Esq., Glasgow.
Kennedy, Benjamin, Esq., F.L.S. , Clapton, Middlesex. King, John, Esq., Ipswich. Kirkpatrick, George, Esq., Isle of Wight. Langford, John, Esq., Lewes.
Leach, G., Esq., F.Z.S., Melina Place, St. John's Wood. Lealand, Mr., Clarendon Street, Somers' Town. Lear, Henry, Esq., Arundel. Leeson, H. B., M.D,, Greenwich.
Leighton, Rev. W. A., B.A., M.B.S.E., Luciefelde, Shrewsbury. Lemon, Sir Charles, Bart., M.P., F.R.S., G.S., H.S., President of R.G.S. of
Cornwall, &c. Leonard, S. W., Esq., M.M.S.L., 83, Upper Stamford Street. Lej'land, R., Esq., Halifax, Yorkshire. Lighton, Rev. Sir Christopher R., Bart., Epsom. Lighton, Thomas, Esq., Clifton. Lindley, John, Ph.D., F.R.S., L.S., H.S., Professor of Botany, University
College, London, &c. Lister, J. J., Esq., F.R.S., &c., Upton, Essex. Lower, M. A., Esq., F.A.S., Lewes. INIarshall, Matthew, Esq., Bank of England. Martin, Major, Ardrossan, Ayrshire. Martin, Thomas, Esq. M.R.C.S., Reigate.
XVI SUBSCRIBERS.
Massey, Mrs., 22, Queen Street, May Fair, London.
Mavighan, James, Esq., Liverpool.
May, Charles, Esq., Ipswich.
Melville, A. Gordon, M.D., M.R.C.S., British Musenm.
Milner, W. R., Esq., M.R.C.S., Wakefield.
Mitten, Mr. William, A.L.S., Hurstpierpoint.
Moggridge, M., Esq., M.B.S.L., Swansea.
Moore, D., Esq., M.R.I.A., B.S.L., &c., Dublin.
Mosley, Sir Oswald, Bart., D.C.L., F.L.S., G.S., &c., Rolleston Hall, Staf- fordshire.
Murchison, Sir R. Impey, G.C.St.S., F.R.S., L.S., G.S., Mem. Imp. Acad. Sc. Petersburg, Cor. R. Inst. France, &c.
Nash, Mr. William, Tunb ridge Wells.
Neale, Thomas, Esq., Tunbridge Wells.
Neison, Francis G. P., Esq., F.L.S., Pall Mall.
Nicholson, Richard, Esq., Rochdale.
Noble, J. W., M.B., Danett's Hall, Leicester.
Northampton, Marquis of, D.C.L., Trust. Brit. Mus., President of the Royal Society, F.L.S., S.A., G.S., &c., 145, Piccadilly Terrace.
Norwood, Thomas, Esq., Hastings.
Ogihie, George, M.D., Aberdeen.
Oldham, Thomas, Esq., M.A., F.G.S., M.R.I.A., &c.. Professor of Geology, Trinity College, Dublin.
Ormerod, W., Esq., Rochdale.
Palmer, W. H., Esq., 24, Bedford Row, London.
Pascoe, F. P., Esq., M.R.C.S., Trewhiddle, near St. Austell.
Peach, C. W., Esq., M.R.C.G.S., Fowey, Cornwall.
Penneck, Rev. H., M.A., Penzance.
Percy, John, M.D., F.R.S., M.B.S.E., Birmingham.
Pim, James, Esq., Dublin.
Plomley, Francis, M.D., Ph.D., F.L.S., &c., Maidstone.
Pollexfen, Rev. J. H., B.A., M.D., 4, Belford Place, Clapham Rise.
Powell, Hugh, Esq., Seymour Place, Euston Square, New Road.
Price, John, Esq., Linen Hall Place, Chester.
Quekett, Edwin J., Esq., M.R.C.S., F.L.S., Lecturer on Botany, &c., 50, Wellclose Square.
Quekett, John Thomas, Esq., M.R.C.S., Royal College of Surgeons, London,
Rand, Mrs., Guildford.
Ranking, Robert, Esq., F.L.S., Hastings.
Ransome, R., Esq., Ipswich.
Reade, Rev. J. B., F.R.S., Stone Vicarage, Bucks.
Reed, Mr. William, Wadhurst.
Reeve, Lovell, Esq., F.L.S., King William Street, Strand.
Reeves, W. W., Esq., Tunbridge Wells.
Riley, John, Esq., M.B.S.E., Papplewick, near Nottingham.
Risk, A., Esq., Paisley.
Robertson, William, Esq., Quayside, Newcastle-on-Tyne.
SUBSCRIBERS. XVll
Robinson, C. M., Esq., Stoke Ncwington.
Rogers, George, M.U., M.R.C.S., Bristol.
Rosling, Alfred, Esq., Ncwington Place, Kennington.
Ross, A., Esq., Featherstone Buildings, Holborn.
Rothwell, Miss, Adelaide Place, Iltracombe.
Ruck, INIr. William, Baths, Clieltenham.
Russell, Frederick, Esq., Brislington, near Bristol.
Russell, Mr. J., Guildford.
Salter, Thomas Bell, M.D., F.L.S., Isle of Wight.
Salwey, Rev. T., M.A., Oswestry.
Sanders, William, Esq., F.G.S., Bristol.
Scott, ]Mr. Robert, Hill Park, Westerham, Kent.
Scouler, John, M.D., F.L.S., Professor of Geology in the Royal Dublin Society.
Shadbolt, George, Esq., Sutherland Street, Walworth.
Sharp, Mr. John, Tunb ridge Wells.
Sidebotham, J., Esq., M.B.S.L., Manchester.
Simpson, S., Esq., F.B.S.E., The Greaves, Lancaster.
Skinner, Mr. Edward, Rye.
Smith, Mr. James, Coleman Street, City,
Smith, Rev. W., F.L.S., &c., Wareham.
Sollit, J. D., Esq., Grammar School, Hull.
Sopwith, T., Esq., F.R.S. & G.S., AUenheads, Northumberland.
Speuce, William, Esq., F.R.S., L.S., &c., Lower Seymour Street, Portman Square.
Stackhouse, Miss Emily, Trehane, near Truro.
Staunton, Sir George Thomas, Bart., M.P., F.R.S., L.S., S.A. & H.S., De- vonshire Street, Portland Place.
Stent, William, Esq., Fittleworth, Sussex.
Sterry, Charles, Esq., Trinity Square, London.
Stokes, C, Esq., F.R.S., L.S., S.A. & G.S., Verulam Buildings, Gray's Inn.
Streeten, Robert J. N., M.D., F.L.S., Worcester.
Stuart, William, Esq., 8, Frederick Street, Gray's Inn Road, London.
Symonds, F., Esq., M.R.C.S., Oxford.
Taylor, Richard, Esq., F.L.S., S.A. & G.S., M.R.A.S., &c., Red Lion Court, Fleet Street.
Tennant, James, Esq., F.G.S., &c., 149, Strand.
Thompson, W., Esq., President of Natural History Society of Belfast, &c.
Thwaites, G. H. K., Esq., M.B.S.L., Lecturer on Botany at the Bristol Me- dical School.
Topping, Mr. C. M., Pentonnlle, London.
Tosswill, Charles S., Esq., 8, Torrington Place, London.
Tovey, Mr., Blechynden Terrace, Southampton.
Tudor, R. A., Esq., M.R.C.S., Liverpool.
Turner, Col. L. H., Argyll Street.
Turner, Dawson, Esq., F.R.S., L.S., A.S., &c. Yaraiouth.
Turner, Henry, Esq., Jeffery's Terrace, Camden Town.
b
XVlll SUBSCRIBERS.
Tyrrell, John, Esq., Totness.
Walcott, W. H. L., Esq., Clifton.
Wallis, Arthur, Esq., Brighton.
Walton, John, Esq., F.L.S., &c., 9, Bamsbury Square, Islington.
Ward, N. B., Esq., F.L.S., Z.S., M.B.S.E., &c., Wellclose Square, London.
Warington, Robert, Esq., Apothecaries' Hall, London.
Wells, W., Esq., Primrose House, Bootle, Liverpool.
West, Mr. Samuel, Tunbridge Wells.
West, W. James, Esq., M.R.C.S., F.G.S., M.B.S.L., &c., Tunbridge.
Westley, Mr., Regent Street.
White, Alfred, Esq., F.L.S., Cloudesley Square, Liverpool Road, London.
Wliite, H. Hopley, Esq., Clapham.
Whitla, F., Esq., M.B.S.L., G.S.D., Belfast.
Wilkinson, M. A. Eason, M.D., M.B.S.E., Manchester.
Williams, Thomas, M.D., Swansea.
Windsor, John, Esq., F.L.S., Manchester.
Winton, F. C, Esq., Beckley, Sussex.
Woods, Joseph, Esq., F.L.S., F.S.xA., G.S., &c., Lewes.
Woodward, Charles, Esq., F.R.S., President of Ishngton Literan,'^ and Scientific Society, 10, Compton Terrace, Islington.
Wright, Thomas, M.D., Cheltenham.
Yarrell, William, Esq., F.L.S., Z.S., &c., Ryder Street, St. James's.
Yates, James, Esq., M.A., F.R.S., L.S. & G.S., Upper Bedford Place, Rus- sell Square.
Young, J. Forbes, M.D., F.Z.S., B.S., &c.. Upper Kennington Lane, London.
ERRATA AND ADDENDA.
Page 61, to synonyms of Desmidium Swartzii, add
Desmidium bispinosumj Corda, Observ. Micros, sur les Animalc. de Carlsbad, p. 20. t. 4. f. 28 (1840). 74, for M. morsa read M. americana (Ehr.), and add the following synonym : Euastrum americanum, Ehrenberg, Verbreiiung und Eiiifluss des Mikros. Lebens in Sud- und Nord-Amerika, t. 4. f. 15 (1843). Substitute americana for morsa twice in the description. 86, line 5, for S. read /3. 99, to synonyms of Cosmarium Botrytis, add
Euastrum interstitiale, Kiitzing, Phycologia Germanica, p. 136 (1845), according to Kiitzing in lit. 101, line 2, dele Sussex. 127, add. Sporangia of Staurastrum hirsutum have been gathered
abundantly at West Point, New York, by Professor Bailey. 130, under Staurastrum pungens, dele the reference to the American
Journal of Science and Arts. 213, under Staurastrum pygmceum, add, Mr. Jenner informs me that he has seen this species amongst other Desmidieae which I had forwarded from Dolgelley ; and Mr. Thwaites has given me its sporangia, gathered near Devonport by Mr. Dansey.
The following additions will render more complete the directions for mounting Alga which have been given in the Introduction.
The rarer species of Desmidieae are frequently scattered amono-st decayed vegetable matter, so that it is difficult to procure good spe-
b2
XX ERRATA AND ADDENDA.
cimens for mounting. In such cases a small portion of the mass should be mixed with a little of the creosote fluid, and stirred briskly Avith a needle. After this has been done the Desmidiese will sink to the bottom, when the refuse should be carefully removed. Successive portions having been thus treated, specimens will at length be pro- cured sufficiently free from foreign matter. Even in ordinary circum- stances, if a small extra quantity of fluid be placed in the cell, and the slide gently inclined, most of the dirt can be removed by a needle before the cell is closed, which process will materially increase the beauty of the preparation.
If the cells are insufficiently baked, the japan occasionally peels off the glass after the specimen has been mounted for some time. To obviate this inconvenience, Mr. Jenner previously heats the cell, with much caution, over a rushlight, until the japan becomes of a dark colour, and vapour ceases to arise from it.
When gold-size is used for closing the cell, the intrusion of some of it frequently destroys valuable specimens, whatever care may be taken : Mr. Jenner has therefore relinquished it, and now employs a varnish made of coarsely comminuted purified shell-lac or translucent sealing-wax, to which is added rectified spirits of wine, in sufficient quantity to cover it. This varnish will be ready for use in about twelve hours ; when it is too thick a little more spirit should be added. Mr. Jenner applies three coats of this varnish, and about a week afterwards a fourth composed o^ japan varnish or yold-size.
I have tried this method extensively, and have never found my specimens spoiled by the varnish insinuating itself into the cell. This process requires less time, and herein it possesses another great ad- vantage over the gold-size method, for the second coat being applied vidthin half an hour, the risk of admitting air into the cell is much diminished.
To preserve the brush in a fit state it should always be cleaned with spirits of wine whenever it has been used.
At page 16 of the Introduction I have stated that I had never wit- nessed the circulation in the Closteria ; but since the printing of that part Mr. Bowerbank has shown me the circulation in Closterium Lu- nula and in Penium Digitus. It seems, at least in the Closterium, to
ERRATA AND ADDENDA. Xxi
be restricted to the space between the mass of endochrome and the integument ; for neither Mr. Bowerbank nor myself could detect it in the internal parts of the endochrome. I at first supposed that the circulation was confined to the margins ; nor did I perceive it else- where until Mr. Bowerbank adjusted the microscope and showed me that the motion extended over the whole surface of the endochrome. The circulation being, as I have just stated, carried on between the integument and the mass of endochrome, which is usually brought fully into view by the observer, explains the difficulty experienced in detecting the circulation, except at the margins. The motion was very irregular : the fluid flowed at one time towards the extremities, and at another in the opposite direction, and the intervals between these changes were of uncertain duration. Streams also, though apparently not separated by any partitions, flowed side by side in contrary di- rections. The currents evidently consisted of an homogeneous fluid; but from time to time minute granules were detached from the internal mass of endochrome and carried along in the stream for short periods, after -va hich they either returned to the quiescent portion or passed into other currents. It seems to deserve particular notice that the circulation was not interrupted at the suture. The process in Penium Digitus was somewhat different from that just described. The flow was continuous from the middle to the extremities, whence the re- turning streams apparently poured back through the centre of the mass of endochrome. I ought however to add that, as regards the Penium, I witnessed the movement only in one specimen, and in that but for a short period. I have subsequently succeeded now and then in obtaining with the triplet some obscure indications of the existence of a circulation ; but for the exhibition of it with any accuracy or certainty the simple microscope seems altogether inadequate.
I have mentioned in the Introduction many points of similarity between Desmidieae and acknowledged Algae, and as every additional fact illustrating the resemblance tends to confirm the opinion advo- cated in this work, that the former belong to the vegetable kingdom, I gladly seize this opportunity of stating that Mr. Jenner has recently shown me in a species of Tyndaridea evident, though faint, longitu- dinal striae, similar to those which are present in many Closteria, and that Mr. Bowerbank has pointed out to me the same appearance in a species of Tiresias.
xxu
ERRATA AND ADDENDA.
Professor Bailey has recently presented me with a collection of American Desmidiese, preserved in Goadby's solution, in small sealed bottles ; one of these, filled with specimens gathered in a pond near Princeton, New Jersey, is so rich in species, that I feel assured a list of them will be very acceptable to my readers, since it adds so many species to the great number which have been recorded in this work as common to both countries.
Hyalotheca dissiliens. Didymoprium Grevillii.
BoiTeri.
Desmidium Swartzii. Aptogonum Bailep. Sphserozosma excavatum.
pulchrum.
Micrasterias fimbriata. radiosa.
rotata.
trimcata.
Torreyi.
fuicata.
muricata.
oscitans.
pinnatifida.
Euastrum oblongum.
crassum.
humerosum.
Didelta.
ansatum.
rostratum.
elegans.
binale.
Cosmarium Cucumis.
pyramidatum.
Phaseolus.
granatum.
crenatum.
ovale.
margaritiferum.
Brebissouii.
tetraophthalmum.
connatiira.
Cucurbita.
Cosmarium orbiculatum.
• moniliforme.
Xanthidium fasciculatum.
ci'istatum.
octocorne.
Artbrodesmus convergens. Staurastrum muticum.
dejectum.
birsutum.
Aracbne.
gracile.
Penium margaritaceum y.
Digitus.
inteiTuptum.
Brebissouii.
Docidium nodulosum.
Ehrenbergii.
Bacuhim.
constnctum. verrueosum. nodosum, verticillatum.
Closteiium Leibleinii.
Diaua;.
didymotocum.
augustatum.
costatum.
striolatum.
Ralfsii. ■
setaceum.
cuspi datum.
Pediastrvim Heptactis.
biradiatum.
elUpticum.
INTRODUCTION.
INTRODUCTION,
Until a recent period, the study of the minute objects which form the subject of this work had been more neglected in this kingdom than almost any other branch of Natural History, and I commenced my researches with the intention of acquiring for myself some fuller and more satisfactory in- formation in regard to disputed points in their history, and also with the hope that I might be able to present to the British Naturalist such a description of our species as seemed necessary towards making the knowledge of them at home keep pace w^ith its advance on the Continent. I soon dis- covered not only that we possessed many species hitherto undescribed, but that various points in their economy, not devoid of interest, remained still unexplained or doubtful ; and, rewarded beyond my expectations, I hastened to com- municate the result of my investigations in a series of papers to the Botanical Society of Edinburgh. As these memoirs have received the gratifying approbation of distinguished naturalists, both in this country and abroad, I have been induced, at the solicitations of my friends, to publish as complete a monograph of the British species as the present state of our knowledge will permit.
The Desmidicce have been for a long time a common terri- tory, claimed both by zoologist and botanist. In consequence, a greater number of persons have devoted themselves to their study, and as they have often entered on the subject with
INTRODUCTION.
different and conflicting views, every fact relating to their history has undergone a more rigorous examination.
The Desmidieee are of an herbaceous green colour ; a few only of the Closteria have the integument coloured, but in all the internal matter is green. All the family are inhabitants of fresh water. Mr. Thwaites indeed has gathered two or three species in water slightly brackish, but the same species are also found in localities remote from the sea. Certain marine objects that have been classed with the Desmidiese have the internal matter of a brown colour, but these, in my opinion, belong to the Diatomaceee.
Their most obvious peculiarities are the beauty and variety of their forms and their external markings and appendages ; but their most distinctive character is the evident'division into two valves or segments.
Each cell or joint in the Desmidiese consists of two sym- metrical valves or segments, and the suture or line of junc- tion is in general well-marked ; in a few instances however, as in Scenedesmus, it is determined principally by analogy. In Pediastrum its situation is shown by a more or less evident notch on the outer side, but no separation has been noticed. The structures of Scenedesmus and Pediastrum are in fact less known than those of the rest of the family ; and of their modes of reproduction we are altogether ignorant. In the other genera the suture eventually opens and allows the escape of the contents, and it is indicated by either a trans- verse hne or a pale band, and usually also by a constric- tion.
An uninterrupted gradation may be traced from species in which these characters are inconspicuous to those in which they are fully developed : thus in Closterium and some species of Penium there is no constriction ; in Tetmemorus, in some Cosmaria, and in Hyalotheca, it is quite evident, although still but slight ; in Didymoprium and Desmidium it is denoted by a notch at each angle ; but in Sphcerozosma, Micrasterias and some other genera, the constriction is very deep, and the connecting portion forms a mere chord between the segments,
INTRODUCTION. 3
which appear like distinct cells, and are so considered by Ehrenberg and others.
When the papers on the Desmidiese were publishing in the * Annals of Natural History,' I stood alone in regarding the frond as a single cell, differing on this point not only from Ehrenberg, but from every author whose works I had seen. Professor Kutzing, however, in his ' Phycologia Germanica,' has by independent observations arrived at the same con- clusion ; an important corroboration of the correctness of the opinion I then advanced. That the frond in Euastrum and allied genera is really a single constricted cell, and not a bi- nate one, will, I am persuaded, be apparent to any one who traces the gradations mentioned above ; but as the opinions of such distinguished naturalists as Ehrenberg and Mene- ghini are deservedly of much influence, and the subject is so important, — since upon the view which we take of it de- pends the explanation of the division of the frond presently to be described, — I shall proceed to notice some facts which seem to me quite decisive.
In Navicula and other genera of Diatomacese the frustules are often truly binate, and, as each frustule is complete in itself, though they be separated from each other their respec- tive contents will still be protected on all sides ; and even should one be broken the contents of the other will be un- disturbed. In the Desmidiese, on the other hand, as there is no septum between the segments, if these separate, or an opening be made in one, the contents of both will escape ; and I have more than once observed the minute granules passing from one segment through the connecting tube into the other. The conjugation of the fronds and formation of sporangia I believe to be altogether irreconcilable with the supposition of binate cells. For in the simple Algse are many examples where the contents of two cells meet and form a compact seed-like mass ; but I. know of no instance in which the contents of more than two cells are thus united : nor does it appear probable that the process of reproduction in either an animal or a vegetable should require, or indeed permit,
B ^
4 INTRODUCTION.
the conjunction of four individuals for that purpose ; but if the fronds were binate, it must follow that the cooperation of four individuals would be necessary for the continuation of the species. In Didymoprium Grevillii the reproductive body is contained within one of the coupling joints ; so that if they were binate we should have the contents of two cells passing into two other cells, the contents of all four uniting into one body, two of the cells at all events forming a single chamber. It may indeed be suggested that the joint in Didymoprium differs from the frond in some of the other genera ; but such a supposition is utterly untenable, and will never be advanced by any one acquainted with these objects. In both the endochrome is divided into two by a pale transverse band marking the junction of the valves ; and here they in both eventually open, and permit the escape of their contents. In the one case, as in the other, the coupling bodies alike com- municate at this point, and the entire process is essentially the same. I will now presume that I have proved that the bipartite Desmidiese are truly cells more or less constricted, and in the following details I shall so designate them.
In the Desmidiese the multiplication of the cells by repeated transverse division is full of interest, both on account of the remarkable manner in which it takes place, and because it unfolds, as I believe, the nature of the process in other fami- lies, and furnishes a valuable addition to our knowledge of their structure and physiology.
The compressed and deeply constricted cells of Euastrum offer most favourable opportunities for ascertaining the man- ner of the division ; for although the frond is really a single cell, yet this cell in all its stages appears like two, the seg- ments being always distinct, even from the commencement. As the connecting portion is so small, and necessarily pro- duces the new segments, which cannot arise from a broader base than its opening, these are at first very minute, though they rapidly increase in size. The segments are separated by the elongation of the connecting tube, which is converted into two roundish hyaline lobules. These lobules increase
INTRODUCTION. 5
in size, acquire colour, and gradually put on the appearance of the old portions. Of course, as they increase the original segments are pushed farther asunder, and at length are dis- connected, each taking with it a new segment to supply the place of that from which it has separated.
It is curious to trace the progressive development of the new portions. At first they are devoid-of colour, and have much the appearance of condensed gelatine, but as they in- crease in size the internal fluid acquires a green tint, which is at first very faint, but soon becomes darker ; at length it assumes a granular state. At the same time the new seg- ments increase in size and obtain their normal figure ; the covering in some species shows the presence of puncta or granules ; and lastly, in Xanthidium and Staurastrum the spines and processes make their appearance, beginning as mere tubercles, and then lengthening until they attain their perfect form and size ; but complete separation frequently occurs before the whole process is completed. This singular process is repeated again and again, so that the older seg- ments are united successively, as it were, with many gene- rations. In Sphserozosma the same changes take place, and are just as evident, but the cells continue linked together, and a filament is formed, which elongates more and more rapidly as the joints increase in number. This continued multiplication by division has its limits ; the segments gra- dually enlarge whilst they divide, and at length the plant ceases to grow ; the division of the cells is no longer repeated ; the internal matter changes its appearance, increases in density, and contains starch-granules which soon become numerous ; the reproductive granules are perfected, and the individual perishes. In a filament the two oldest segments are found at its opposite extremities ; for so long as the joints divide they are necessarily separated further and further from each other. Whilst this process is in progress the filament in Sphserozosma consists of segments of all sizes ; but after it has reached maturity there is little inequality between them, except in some of the last-formed segments,
6 INTRODUCTION,
which are permanently smaller. The case is the same with those genera in which the separation of the cells is complete. I admit that the division of the cells just described apparently differs greatly from that in other simple Algae ; but I believe that the process in all is essentially the same, and that what- ever differences exist are modifications necessarily resulting from the different forms of the cells. In the examples already given the cell itself consists of two distinct portions, having a constriction between them ; hence each of the new-formed portions is similarly distinct from the older one which forms it and to which it is united.
In order fully to elucidate the subject, cells may be distri- buted into three principal kinds, distinguished by their form :
1st. Bipartite cells, already described, and more or less constricted at the middle ;
2nd. Cells globose or rounded at the ends, or having the extremities attenuated ;
3rd. Cylindrical cells.
Bipartite cells belong only to the Desmidieee ; cells globose or roundish at the ends are seen in the Nostocs and Palmellese ; attenuated cells in the Desmidiess ; and cylindrical ones in the Conjugatse, Tiresias, &c.
It is obvious that the new portions must arise from the whole of the junction margin of the original valves ; conse- quently when the junction occupies only a part of the breadth the new portion will be narrower than the old ; but when the junction of the valves is as broad as the cell, the new portion will from the beginning be of the same breadth. From this important fact, we may explain the different sorts of division. Since in the two latter kinds of cell the valves are united by their entire breadth, the new portions cannot be distinguished by their size, we must therefore have recourse to other aids to enable us to trace the changes and satisfy ourselves of their real identity with that already described ; and I hope to be able to show that this identity does exist.
In Nostoc and Anabaina the cells are globular, and as there is no constriction we might remain ignorant of the real me-
INTRODUCTION. 7
thod of division ; but, guided by the analogical process in the Desmidiese, I hope to make it sufficiently plain. The hemi- spheres are thrust apart by the new formation ; but now it is the outer rounded margin that we look to for an explanation. If a globe be cut into two equal portions, each will represent half a circle. By comparison with the neighbouring cells, we find that these two half circles remain unaltered, and are merely separated from each other, for if again brought together they would reconstitute the former globe. The new formations however separate them further and further, until the intervening space equals that occupied by the original globe, and then we find two globes exactly like the primary one, the internal half of each being the newly-formed one. During this time the inner portions, as they extend, develope more and more of the circle, until each becomes, as I have stated, a perfect hemisphere. The whole process cannot, of course, be seen in the same cell ; but in a dividing filament some joints may be observed in one stage and some in another, which renders the evidence complete.
When the cell is oblong, or only rounded at the extremi- ties, the process, though similar, is less evident : the cell at first seems merely to elongate until it obtains nearly twice its original length, when the division commences and the round- ing of the new ends becomes apparent. The tapering cell presents but little difference, for the separation takes place before its extremities are fully developed. Sometimes these cells separate obliquely, as in Spirotsenia and Scenedesmus.
I ought to state however that the opinions advocated above do not agree with those of M. De Brebisson, who has at- tained so high a reputation for his intimate acquaintance with the freshwater Algee, and to whose kindness I have been so often indebted during the progress of the present work. He considers that there is an essential distinction in the mode of division between the Desmidiese and Nostochinese (including in the latter the Palmelleee), and that from it in- deed differential characters are obtained bv which we can
8 INTRODUCTION.
distinguish these nearly-allied groups. He observes of Hor- mospora mutabilis, Breb.*, " lis sont le plus souvent gemines, se multipliant par une division spontanee (deduplication) transversale, comme cela arrive dans quelques autre s Pleuro- coccoidees. Une division analogue a lieu dans les Desmi- diees, auxquelles on serait d'abord tente de rapporter les Hormospora; mais les demi-corpuscules (hemisomates) des Desmidiees developpent k leur point de separation une nouvelle portion semblable a la premiere, tandis que, dans I'accroissement des Nostocinees, les corpuscules sont di vises en deux par un etranglement transversal, sans qu'il s'ensuive une reproduction sur chacun des points de rup- ture. II y a dans ce cas, comme je I'ai dit ailleurs, dedupli- cation simple. Dans les Desmidiees, il y a deduplication et re'duplication.''
It is with unfeigned diffidence that I venture to dissent from the opinion of one possessing so profound a knowledge of these tribes, and I do so only from conviction, the result of close and repeated investigations.
I have stated my belief that the same changes occur in both the Desmidiese and the Nostochinese. A cell in Micras- terias has two hemispheres, just as a joint in Anabaina has ; in both these separate, and in both each hemisphere becomes again a perfect sphere ; and if in Micrasterias the two hemi- spheres were united by their whole bases, there would not remain even an apparent difference between them.
The form of the cylindrical cells no longer helps us in tracing the method of division. In Penium as in the Conju- gatee, they seem merely to elongate and then divide. As I for- merly suggested, in a paper read before the Botanical Society of Edinburgh, I consider it extremely probable that in all the simple Algse the cell or joint consists of two valves, and that additions occur at their junction, the original parts remaining unaffected : but this it may never be possible to
* Annales des Sciences Naturelles, Jan. 1844.
INTRODUCTION.
demonstrate satisfactorily, unless a species of Conferva with a coloured integument should be detected, or some means can be devised for permanently colouring the filaments with- out impairing their growth. Then indeed the question might be determined ; at present I can merely show the probability that the cell in cylindrical species of Desmidiese agrees with the joint in a Zygnema or Tyndaridea ; since whenever the covering is colourless and free from markings not the slightest difference can be perceived. This is the case in a few species of Penium ; and hence Penium Brehissonii is by some authors placed in the Palmellese. In Penium margaritaceum and Penium Cylindrus the integument is coloured, and we are enabled, by means of the paler appearance of the newly- formed portions, to satisfy ourselves that in these also each half of the original cell is acquiring during the division a new partner. In Didymoprium the same fact is rendered apparent, because the suture passes between minute teeth ; these teeth recede from each other, and the new teeth which appear between them show the place where the separation of the joint has occurred.
The spontaneous division of the frond is included by some writers amongst the modes of reproduction ; but this is not strictly correct, for it is rather the manner in which the in- dividual plant grows, since all the cells arrive at maturity nearly at the same period and terminate their existence about the same time.
The Desmidiese are most probably reproduced only in two modes ; one by the escape of the granular contents of the mature frond, and the other by the formation of sporangia, the result of the coupling of the cells.
When the cells approach maturity, molecular movements may be at times noticed in their contents, precisely similar to what has been described by Agardh and others as oc- curring in the Confervee. This movement has been aptly termed a swarming. It has been sieen by numerous ob- servers,— in this country by Messrs. Dalrymple, Jenner, Thwaites, Sidebotham, Dr. Dickie, and others. The cause
10 INTRODUCTION.
of this sudden commotion cannot be ascertained ; but I have met with it more frequently in specimens that have been kept some days than in fresh-gathered ones. When released by the opening of the suture, the granules still move, but more rapidly and to a greater distance. With the sub- sequent history of these granules I am altogether unac- quainted, but I conclude that it is similar to what has been traced in other Algae.
The second mode of reproduction is by coupling, and the formation of sporangia. A communication is established between two cells, and a seed-like mass is formed in the same manner as in the Conjugatse. This is green and gra- nular at first, but soon becomes of a homogeneous appear- ance and of a brown or even reddish colour. There are however some variations in the process in the two families which require notice. In the Conjugatse, the cells conjugate whilst still forming parts of a filament ; but in the Des- midiese, the filamentous species almost ipvariably separate into single joints before their conjugation, and in most of the species the valves of the cells become detached after they are emptied of their contents.
In many genera the sporangia remain smooth and un- altered ; in others they become granulated, tuberculated or spinous ; the spines being either simple or forked at the apex. In fact a sporangium may pass successively through all these stages, and hence may so change its appearance that its different states are liable to be taken for sporangia belonging to different species. In Tiresias also we sometimes meet with sporangia bearing spines, but in that genus they are arranged like the spokes of a wheel, and not scattered as in the Desraidiese. What is the nature of the sporangia, and why so complicated a process is necessary, since the species is also propagated by means of the granules or zoo- spores which escape from the ruptured cell, are questions to which we cannot, in the present state of science, return a satisfactory answer. The sporangia I consider capsules ; and this view seems to be confirmed by the experience of
INTRODUCTION. 1 1
Mr. Jenner, who informs me that the covering of the spo- rangium swells, and a mucus is secreted, in which minute fronds appear and, by their increase, at length rupture the attenuated covering*. That some purpose distinct from that performed by the zoospores is served by the coupling of the cells and formation of the sporangium cannot be doubted : for, where we can trace the operations of nature, we find that nothing is useless or in vain ; nor is it reasonable to suppose that this complicated process should fulfil no other purpose than one already provided for without it. The sporangia are most abundant in spring before the pools dry up ; and I would suggest, as no improbable conjecture, that the zoo- spores may be gemmae, analogous to those present in Mar- chantia polymorpha and Lunularia vulgaris, and that they possess merely a limited vitality, which is destroyed unless they are at once placed in circumstances favourable to their growth, whilst on the other hand, in the conjugated cells some important change takes place during the commingling of their contents and the formation of the sporangium, like what happens in the production of seeds in general, which renders the sporangia capable of retaining the vital principle uninjured throughout long periods of drought.
That the Closteria couple and produce sporangia, in a manner similar to the Conjugatse, has been recorded by Turpin and other writers. Correct figures of some species in that state are given by Ehrenberg in his ' Infusoria,' and Mene- ghini mentions thatBrebisson had detected it in Desmidiumf , but I am not aware that the conjugation of other Desmidiese was :i<)ciced by any writer before I published in the ' Annals of Natural History' full descriptions of the formation of sporangia in Tetmemorus granulatus and Staurastrum mucro- natum. Subsequently examples have been detected in almost every genus, and we cannot hesitate to consider it charac-
* An example of this condition occurring in Closterium acerosum is figured in the Plate containing that plant.
t " Diatomatum more secedunt, hasque simul e latere copulari in speciebus nonnuUis detexit cl. Brebisson." — Meneghini, Synop. Desmid. p. 203.
12 INTRODUCTION.
teristic of the family. In this country the conjugation of about forty species has been noticed by different observers, and M. De Brebisson informs me that he has gathered spo- rangia of the following species in France : — Hyalotheca dis- siliens, Didymoprium Grevillii, Staurastrum pygmcpum, S. con- troversum, S.muticum, Cosmarium Botrytis, Closterium Lunula, C. setaceum, C. acutum, and C lineatum.
In defining the genera and species, I have made no use of the reproductive bodies, for as yet too little is known about them to render them available for that purpose, and in many cases we are still uncertain whether the mature form is yet known. They are likewise so early detached from the emptied cells, that it is often very difficult to determine to what species they belong*.
I have gathered sporangia of other species besides those mentioned in this work ; but whenever they were not still adherent to the fronds I have thought it best to pass them over, lest I should be the cause of error.
That the orbicular spinous bodies so frequent in flint are fossil spoi'angia of Desmidieae cannot, I think, be doubtful when they are compared with figures of recent ones. Indeed one celebrated geologist. Dr. G. Mantell, who, in his ' Medals of Creation,' without any misgiving had adopted Ehrenberg's ideas concerning them, has changed his opinion, and in his last work regards them as having been reproductive bodies, although he is still uncertain whether they are of vegetable origin.
Ehrenberg and his followers describe these bodies as fossil
* A principal use of generic and specific characters is to enable us to identify the species we meet with ; and although a genus may be accurately defined by characters taken from the reproductive parts, yet if that definition can be tested only in a few rare instances, it will be inferior in real value to one which is derived from less important parts that are always present. My wish has been to render the present work a practical one, useful in the fields as well as in the study : I have therefore omitted the employment of such characters, and endeavoured to express those which I have adopted as con- cisely as may be compatible with usefulness.
INTRODUCTION. 13
species of Xanthidium, but no doubt erroneously, since their structure is very different. For the true Xanthidium has a compressed, bipartite, and bivalved cell, whilst these fossils have a globose and entire one.
The fossil forms vary like recent sporangia in being smooth, bristly, or furnished with spines, which in some are simple, and in others branched at the extremity. Some- times too a membrane may be traced, even more distinctly than in recent specimens, either covering the spines or entangled with them.
Some writers describe the fossil forms as having been siUceous in their living state, but Mr. Williamson informs me that he possesses specimens which exhibit bent spines and torn margins, and thus wholly contradict the idea that they were siliceous before they were imbedded in the flint.
In the present state of our knowledge it would be pre- mature to attempt identifying the fossil with recent species : it is better therefore, at least for the present, to retain the names bestowed on the former by those who have described them. A paper on fossil Xanthidia by Mr. H. H. White, containing descriptions of eleven supposed species, accom- panied by characteristic figures, may be consulted with advantage*.
In all the Desmidiese, but especially in Closterium and Micrasterias, small, compact, seed-like bodies of a blackish colour are at times met with. Their situation is uncertain, and their number varies from one to four. In their imme- diate neighbourhood the endochrome is wanting, as if it had been required to form them, but in the rest of the frond it retains its usual colour and appearance. I cannot satisfy myself respecting the nature of these bodies, but I believe them either to arise from an unhealthy condition of the plant, or else to be parasitic.
The only account I have seen of the discovery of fossil
* Microscopic Journal, vol. ii. p. 35.
14 INTRODUCTION.
fronds of Desmidieee is by Professor Bailey, who detected various species of Closterium and Euastrum in calcareous marls, collected in New Hampshire and New York by Pro- fessors Hubbard and Hall, and also in marl at Scotchtown, New York, by Mr. Connors*. Professor Bailey informs me, that the specimens from the last-named station, and in which he found several Closteria, Euastra, &c., were taken from below the bones of the Mastodon giganteus. As sporangia of the Desmidieae and other membranous bodies in a fossil state have lately been detected by Mr. Deane and Dr. G. Mantell in the grey chalk of Folkestone, it is probable that a careful search in that neighbourhood would also bring to light the fossil fronds of the Desmidieae.
The production of the Desmidieae in newly-formed col- lections of water is involved in obscurity. The late Mr. Miller of Penzance pointed out to me an instance of this kind well-worthy of notice. He found Hyalotheca dissiliens and other species of this family in an old water-butt, which stood in a yard remote from any apparent station for the Desmidieae, and derived its water from the clouds alone ; and the question naturally arises, How came the Algse there ? The theory of spontaneous generation has never obtained currency in this kingdom, and for my own part I am not unwilling to acknowledge that there are mysteries in nature which we cannot penetrate. I can therefore only attempt to account for the appearance of the Desmidieae under such circumstances in two w^ays, — ^by supposing either that the atmosphere contains countless myriads of the sporules of the Desmidieae and other Cryptogamia, which vegetate only when they meet a congenial situation, or that the seeds are conveyed by means of aquatic insects, many of which, it is well known, roam during the night by means of their wings from one piece of water to another. The latter I consider the more probable conjecture.
The entire question of the vegetation of the conjugating
* American Journal of Science and Arts, vol. xlviii. p. 340.
INTRODUCTION. 15
Algse is far from being understood. A few years back I paid considerable attention to the subject, but without arriving at any satisfactory conclusion. The Staurocarpus ccerulescens is not uncommon near Penzance, is generally in large quan- tity where it occurs, and, from its peculiar colour, cannot escape detection ; on these accounts I made it a principal subject of my observation. Although I have yearly gathered it in several pools, and the sporangia are always abundantly produced, I have particularly noticed during five or six years' observation, that it has never in a single instance re- appeared in the same pool. At Dolgelley, where also in some years it is common, Imet with the same result, with a single exception when I gathered it in one pool for two successive years. I have noticed the same fact with regard to Zygnema curvatum, and I believe it holds good in regard to most if not all the other Conjugatse ; but as they are more liable to be overlooked, I cannot speak of them with the same cer- tainty as of the above-mentioned species. Algae in running water commonly recur every season. I called Mr. Jenner's attention to the subject : we were alike unsuccessful in our attempts to ascertain the cause of this singularity. His observations in general agreed with mine, that the plant will not appear in the same pool for two successive years ; but he found too many exceptions to justify any certain con- clusion.
All the Desmidiese are gelatinous. In some the mucus is condensed into a distinct and well-defined hyaline sheath or covering, as in Didymoprium Grevillii and Staurastrum tu- midum ; in others it is more attenuated, and the fact that it forms a covering, is discerned only by its preventing the contact of the coloured cells. In general its quantity is merely sufficient to hold the fronds together in a kind of filmy cloud, which is dispersed by the slightest touch. When they are left exposed by the evaporation of the water, this mucus becomes denser, and is apparently secreted in larger quantities to protect them from the effects of drought. I have observed more especially that Tetmemorus granulatus
16 INTRODUCTION.
and Penium Brehissonii, under such circumstances, form a distinct mucous stratum ; and on this account some authors have placed the latter with the Palmellese, although when it occurs in water it is less gelatinous than many other species belonging to the family of the Desmidiese.
I have never obtained a clear view of the circulation wit- nessed by various authors in species of Closterium and Doci- dium, but I have no doubt that it is correctly described in the following account by Mr. Dalrymple of his own obser- vations : — " A circulation of the fluids within the shell was observed independent of the active molecules ; this was regular, passing in two opposite currents, one along the side of the shell, and the other along the periphery of the gela- tinous body*." Professor Bailey observes, that "The account by Mr. Dalrymple agrees with what I have witnessed in several species. The currents are very distinct ; so much so in fact, that they attracted my attention before I was aware that they had been noticed by others f."
Dr. Williams of Swansea has kindly translated from the German a paper on this subject by Labarzewski j, but it is too long for insertion here, nor would it be intelligible with- out the accompanying figures. Labarzewski's observations were made on specimens of Closterium Lunula. The circu- lating fluid was clear and thick, and filled the space between the covering and the central mass of green granular ma- terial, from which granules detached themselves from time to time, and after moving along the margins, returned to their former situation. The current was quickened at the ends and near the suture, where it was lost, but reappeared in the other segment. The circulation was intermittent, lasting each time about seven seconds.
I now approach a question on which I feel the greatest anxiety, lest I should not do justice to the arguments of those from whose opinion I may diflfer, or should fail satis-
* Annals of Natural History, vol. v. p. 416.
t American Journal of Science and Arts, vol. xli. p. 300.
X Linnaea, 1840, p. 278.
INTRODUCTION. 17
factorily to impress upon my reader the reasons which have appeared to my own mind incontrovertible.
The question is, — are the Desmidiese animals or vege- tables ?
The arguments 1 have seen advanced in support of their animal nature appear to me so inconclusive, when contrasted with those adduced in favour of their being vegetables, that, although in the course of a long scientific correspondence I have sought to become thoroughly acquainted with the facts rehed upon by the advocates of the former opinion, I have at times almost doubted whether my distance from the metropolis may not have precluded me from the oppor- tunity of hearing others of a more convincing description.
I will however claim the merit of being at least desirous of stating the case impartially, and I have in vain consulted some distinguished naturalists who differ from me, that I might learn whether their opinions were supported by other reasons than those w^hich are so generally known, and to which I shall presently refer. I will also add, what may be a fact of some weight, that I formerly considered the Des- midiese animals, and the Diatom acese vegetables, and that careful observations alone have in a great measure reversed my opinions. The Desmidiese I now believe have as strong a claim as the Conjugatse or Palmellse can have to rank with the Algae. On the other hand I consider the proper station of the Diatomaceae very doubtful. They have at least as much right to a place in the animal as in the vegetable king- dom ; and perhaps the safest course would be that adopted by several celebrated continental naturalists, who regard them as belonging to a distinct and intermediate group, and partaking almost equally of the characters of animal and of vegetable.
The chief reasons advanced by Ehrenberg and others for placing the Desmidiese in the animal kingdom are the fol- lowing : — that they exert a voluntary motion ; that they in- crease by transverse self-division ; and that the Closteria have at their extremities apertures and protruding organs
c
18 INTRODUCTION.
continually in motion. Although two of these reasons apply only to the genus Closterium, I freely admit that if the Closteria can be proved animals, the question as to the other genera will be decided.
Few indeed hint at such a motive for adopting the opinion, nevertheless I feel persuaded that the animal-like forms of the Desmidicce have had a great, though not avowed, in- fluence on the determination of this question. Did we trust solely to the eye, we should conclude that objects so different in form and variable in appearance, were far more like ani- mals than vegetables. Their symmetrical division into two segments ; the beautiful disciform, finely-cut and toothed Micrasterias, the lobed Euastrum, the Cosmarium glittering as it were with gems, the Xanthidium armed with spines, the scimitar-shaped Closterium embellished with strise, the Desmidium resembling a tape-worm, and the strangely insect- like Staurastrum sometimes furnished with arms, as if for the purpose of seizing its prey ; — all these characters seem in- deed to pertain more to the lower animals than to vegetables. We are thus induced, however unconsciously, to judge be- fore examination, and we naturally search for arguments in support of our preconceived opinion instead of those which may elicit the truth. But experience has proved that form alone is a most deceptive guide, the implicit dependence on which has, in many similar instances, been the cause of error ; and I believe that if a person unacquainted with what has been written respecting the two groups should look at the representations of the Desmidiese, and examine the grace- ful and arborescent Zoophyte, having its branches to all appearance loaded with fruit that is periodically produced, matured, and shed, he would without hesitation place the Desmidiese in the animal, and the Zoophyte in the vegetable kingdom. Nor could we wonder at such a decision, since in former times, even observers of high scientific attain- ments, judging by external appearances, did in fact class Zoophytes with the Algae.
Again, Ellis, who first established the animal nature of
INTRODUCTION. 19
the Zoophytes, and thus dispelled one error, presently com- mitted a similar fault by transferring along with the Zoo- phytes (simply on account of their agreement in certain external characters), Corallina and other genera which, it is almost unnecessary to add, have not until a recent period been restored to their proper place amongst the Algoe*. The above is a sufficient illustration of the danger of trusting solely to the evidence of sight : I shall endeavour to show that it would in the present case also lead to an incorrect conclusion.
That the Desmidiese have been so long associated in the same family with the Diatomaceee, whose proper position is so doubtful, presents another obstacle to the recognition of the claims of the former to rank with the Algae. For when so many eminent observers, — botanists and zoologists, not- withstanding they differ widely in respect of the department of Natural History to which these forms should be assigned, — concur in classing them together, we naturally suppose that there must be valid reasons for such a course. I shall therefore point out the distinctions between these groups, and show that, at all events, they can no longer be united in one family, but must be separated, as they have been by Kutzing in his more recent work, as well as by others.
I have shown that the cell in the Desmidiese consists of two valves united by a central suture, and that during its division the new-formed portions are interposed between these valves. The Desmidieae are membranous, or should a few species contain silica, it is not present in sufficient quan- tity to interfere with their flexibility. They rarely have acute angles, and are seldom (if ever) rectangular. They are often deeply incised or lobed, warted or spinous. The internal matter is of a herbaceous-green colour, and starch vesicles abound in the mature cell. They couple and form either orbicular or quadrate seed-like bodies, and are remarkable for the resistance which they oppose to decomposition.
* See the introductions to Johnston's admirable works on the British Zoophytes and Corallines.
c2
20 INTRODUCTION.
In all these respects they differ from the Diatomacese. In the latter each frustule consists of three pieces, one central and ring-like or continuous all round, and the others lateral. The division is completed by the formation of new portions within the enlarged central piece, which then falls off, or else by a new septum arising at the centre ; but I believe that, in every case, the separation commences internally before it extends to the covering*. Their coverings, with very few exceptions, are siliceous, withstand the actions of fire and acids, and may be broken but not bent ; the frustules are often rectangular in form, are never warted, and scarcely ever spinous. Their internal matter is usually brown when recent ; and, although some species are greenish, or become green after they have been gathered, none are of a truly herbaceous colour. Their vesicles bear some resemblance to those in the Desmidieee, but they are of a yellower colour, and no starch has been detected in them. The Diatomaceae do not conjugate!, and in general they very soon give out an offensive odour.
I have preferred treating of these topics first and at some length, because I wish the reader to enter upon the subject unprejudiced, so that after a fair examination of the con- flicting arguments he may be ready to surrender his judge- ment to that which is supported by facts of greater weight.
The first reason advanced by Ehrenberg in support of the animal nature of the Desmidiese is, that they possess a " voluntary motion ;" but I must protest against his use of the term voluntary as prejudging the matter in dispute and as- suming more than in the present state of knowledge can be ascertained ; more indeed than he has attempted to prove.
That the Desmidiese move must be admitted ; for this fact has been noticed by too many accurate observers to permit
* For detailed descriptions of the mode in which cells are multiplied by division in the Diatomaceae, see the Transactions of the Botanical Society of Edinburgh, vol. ii. p. 37.
t Since the above was in type Mr. Thwaites has detected four species of Diatomaceae in a conjugated state ; the sporangia are elongated and in pairs, and the internal matter is similar to that of the frustules.
INTRODUCTION. 21
any doubt of its truth, and although I have myself failed to perceive their actual movement, I have sufficient evidence of its occurrence. But, whilst making this admission, I must still maintain that in the lower tribes of organic life motion is not an indubitable sign of an animal nature*, and that the movements of the Desmidiese must be very sluggish, or exercised only under peculiar circumstances, since T have never witnessed it, notwithstanding I have almost daily living specimens under my inspection. Mr. Jenner has been equally unsuccessful, and several friends, experienced in the use of the microscope, either have not seen it or speak of it in uncertain terms f.
Professor Bailey states that " their power of locomotion
* " Motum non determinare limites regni animalis exinde patet, quod sunt animalia, quae non moventur, vegetabilia in quibus motum vividum videmus." Agardh, Conspectus Diatomacearum, p. 4.
" The active motions in plants and their parts, especially in Algae, ought not to give rise to the supposition of an animal nature, even when they are called infusorial or animal motions." — Ehrenberg, Taylor's Scient. Mem. vol. i. p, 5S6.
t I subjoin the opinions of various observers : —
" Actual motion, arising from internal causes, I saw only in Sphserastrum ; and the slight movement, supposed to have been observed in some of the genera, is certainly of the same description as that of some Confervse." — Meyen, 1839, as quoted in Pritchard's Infusoria, p. 180.
" These are animals instead of plants, if the faculty of locomotion w^ill entitle them to that rank." — Carmichael, in Hook. Br. Fl. vol. ii. p. 398.
" It was impossible to determine whether the vague motions of Closterium were voluntary or not." — Dalrymple, see Annals of Nat. Hist. vol. v. p. 417.
*' Motions apparently voluntary are easily seen .... I have seen Euastrum margaritiferum move quite distinctly." — Bailey, American Bacillaria.
" EUes n'ont pas un mouvement sensible sur le porte objet du microscope. Cependant il est facile de remarquer dans les localites ou elles vivent ovi dans les vases ou on les conserve, qu'elles se dirigent vers la lumiere et se rapprochent en pellicules oii en sortes de pinceaux d'un beau vert, reunies entre elles au moyen d'un mucus qui les entoure ordinairement." — Brebisson, in Chevalier's ' Des microscopes et leur usage.'
" The various species of Closterium, as well as the closely allied Euastra. have a distinct motion which cannot be referred to any extrication of gas. I have had species of Closterium and Euastrum confined in a compressor, in •water perfectly free from other bodies, and they moved so fast that I found it impossible to sketch their forms by the camera lucida until they were killed." — Professor Bailey in lit.
22 INTRODUCTION.
may be rendered apparent by taking a portion of mud covered with Closteria, placing it in water exposed to light, and then if the Closteria are buried in the mud they will soon work their way to the surface, covering it again with a green stra- tum*," I have myself frequently observed this fact, espe- cially in Tetmemorus granulatus and Penium Brebissonii ; but I presume that it is owing to the stimulus of light rather than to any voluntary effort ; at any rate the same result w^ill follow if an Oscillatoria be substituted for the Closterium. In like manner, in some species of Nostoc, Anabaina, and Palmella, the filaments or cells throng towards the light ; and should the specimen be turned over, they will in a few hours appear on the new surface, whilst they have become less nu- merous on the previous upper one. Of course the gelatine must be in a sufficiently lax state to permit such a movement.
Another proof of their power of locomotion is afforded by their retiring, in some instances, beneath the surface when the pools dry up. I have taken advantage of this circum- stance in order to obtain specimens less mingled with foreign matters than they would otherwise have been. If a species be much mixed with mud, I take a saucer, fill it with earth made into a paste with water, and cover it with a piece of linen ; over this I spread a thick layer, containing the Des- midiese, and allow it to become nearly dry ; within a few days the specimens will form a stratum on the linen, and may be scraped off with a knife. This plan however proves suc- cessful only with the smaller species, and minute Algae ac- company the Desmidiese which are so obtained.
It is thus evident that whatever be the motive power of the Desmidiese they possess it only in common with acknow- ledged Algae, and in a less degree than either the Diatomacese, the Oscillatorieae, the sporules of various Algse, or indeed their own sporules.
Ehrenberg considers that increase by voluntary division is the character which separates animals from vegetables!, and,
* American Bacillaria, in American Journal of Science and Arts, vol. xli. p. 300.
t Annals of Natural History, vol. ii. p. 123.
INTRODUCTION. 23
in fact, he produces no other reason for denying the vegetable nature of some genera. But it will probably be thought a sufficient answer to mention that Meyen and others have proved the growth by elongation and bisection of the cells to be very frequent, if not universal, in the more simple
AlgcE*.
Meyen remarks that Ehrenberg has interpreted "all the facts known as if these creations were undoubtedly animals, whilst the same facts would indicate quite a different signi- fication if we proceeded upon the supposition that they were nothing but plantst-" In the present instance we have a striking example of the truth of this observation, since Ehrenberg, on observing that division occurs in the lower animals, too hastily draws the inference that only animals can be the subjects of it.
On the other hand, Mr. Shuttleworth, in a letter to Mrs. Griffiths, written in the spring of 1842, described the growth of the simple Algse by repeated spontaneous division of their cells, and illustrated it by sketches of Zygnema nitidum, &c. He states that the process is most evident in the Oscillatorise, in Conferva fugacissima, in Lynghya muralis, and in the Con- jugatee; and, after noticing the similar process in the Dia- tomaceee, he adds, " I trust that now their vegetable nature is beyond all doubt ;" thus showing that from the same pre- mises two able observers came to exactly opposite conclu» sions. It is right to mention that Mr. Shuttleworth did not claim the credit of being the original discoverer, but merely said that he had convinced himself of the correctness of the facts published.
To Mr. Hassall is justly due the credit of first directing the attention of British naturalists to this mode of growth ;
* " The increase by self-division occurs in all these genera ; this process is looked upon by Ehrenberg as one of the strongest and most decisive cha- racters of animal nature ; but I have elsewhere proved, in the most satisfac- tory manner, that self-division is very common, both in the low^est plants as well as in the elementary organs of the more highly developed ones." — Meyen, 1839 ; see Pritchard's Infusoria, p. 180.
t See Pritchard's Infusoria, p. 178.
24 INTRODUCTION.
and, as it appears he was not aware that it had previously been noticed by continental botanists, another proof is thus afforded that it has attracted the attention of independent observers.
The fact of the transverse bisection of the Algse is now so well established that this character is employed by J. G. Agardh, in his generic definitions*.
In a preceding part of this introduction, I have endea- voured to show that in the Desmidiese the process is the same as in all the simple Algae.
If some should think that I have dwelt too long upon this topic, I trust I shall stand excused when it is considered that the celebrated Ehrenberg places much reliance upon this character, and that great weight is justly allowed to the authority of one who has devoted so much time and skill to the examination of the Desmidieae ; moreover, that his argu- ments are familiar to the British naturalist, and his opinions extensively embraced, whilst the opinions of those who differ from him on this subject are comparatively unknown.
I am not in a position either to deny or to affirm with con- fidence the presence of openings in the extremities of the Closteria, for in objects so minute it is very difficult, fre- quently perhaps impossible, to distinguish between a depres- sion and an openingf. It appears indeed to me that in Closterium there is a slight notch, or more usually the rudi- ment of one, at the apex of the segments, a mere indication in short of what is fully developed in Tetmemorus and Euas- trum ; for in C Diance, and some other species, there is an evident though minute notch, and in Penium not even a trace of it can be detected. In no instance can any portion of the contents of the cell be forced out from the extremities.
* " Tiresias, fronde tota homogenea et articulis omnibus continua subdi- visione iterum itenimque divisis, atque coniocystis inclusis insigne." — Ag. Icon. Alg. Ined.
t " No one accustomed to the use of the microscope can be otherwise than aware how much very minute objects seen under a high power are apt to as- sume a character in accordance with preconceived notions." — J. T. Smith, in Annals of Natural History, vol. xix. p. 2.
INTRODUCTION. 25
Mr. Dalrymple believes that orifices exist which are closed by internal membranes.
Ehrenberg, on the contrary, describes not merely open orifices, but protruding organs or feet immediately behind them, and thus affords an example of his want of caution when he gives the rein to his poetic fancy ; for in this in- stance at least he is clearly in error. Mr. Dalrymple, whose remarks on the Closteria are the undoubted result of careful examination, carried on with the desire of recording actual facts rather than of supporting a theory, denies the exist- ence of any papillae or proboscides at this part, and also the supposition of Ehrenberg, that the moving molecules seen near the extremities constitute the basis of such papillae. This admission is the more valuable as coming from a person who is not only an accurate observer but a believer in their animal nature. Professor Bailey also informs us that he has failed to detect them.
In most of the Closteria there is at each extremity of the endochrome a distinct globule containing moving granules. Ehrenberg seems to have mistaken these for organs of mo- tion. In Closterium rostratum and C setaceum these granules are situated at a distance from the extremities, and, as they are apparently not contained within a globule, move more freely and afford better opportunities for observing them than those in the other species do. In one instance I saw them continue to move after escaping from the frond. Did the Closteria possess mouths we should expect to find them in every species ; but Penium interruptum, in which there are conspicuous terminal globules and moving granules, has de- cidedly nothing of the kind ; and as its end view is circular and rather turgid no more desirable plant could be selected for examination. If mouths are present they ought to be visible in this and the allied species, but not a single punc- tum can be detected in the end view of the empty frond.
I have now passed in review the four points advanced by Ehrenberg in support of the animal nature of the Desmidieae, and I submit that I have shown that from them no evidence
26 INTRODUCTION.
approaching to a satisfactory proof of his position can be deduced. In offering these remarks I hope I shall not be suspected of the least wish to undervalue Ehrenberg'sdis- coveries. I believe that he is sometimes too hasty in arriving at his conclusions, and that his knowledge of the Desmidiese is less accurate than of the Diatoraacese and other tribes which have come under his observation. When we consider the extent of his researches, it is not surprising, eminent as he is, that he should fall into some errors, which a person inferior in ability, but confining his whole attention to a comparatively smaller range, is likely to detect. Nor even in respect of this family, although I must consider it the most defective portion of his great work, are the obligations slight which we owe to Ehrenberg : for not only has he enlarged our knowledge of the Desmidiese by the discovery of many new facts, by his discrimination of the species, and by producing better representations than those which pre- viously existed, but he has given an impulse to the study, and rendered it popular.
The fifth volume of the 'Annals of Natural History*' contains an abstract of a paper by Mr. Dalrymple on the Closteria, read before the Microscopical Society of London, from which I quote the following reasons for placing them in the animal kingdom : —
" 1st. That while Closterium has a circulation of mole- cules greatly resembling that of plants, it has also a definite organ, unknown in the vegetable world, in which the active molecules appear to enjoy an independent motion, and the parietes of which appear capable of contracting upon its contents.
"2nd. That the green gelatinous body is contained in a membranous envelope, which, while it is elastic, contracts also upon the action of certain reagents whose effects cannot be considered purely chemical.
" 3rd. The comparison of the supposed ova with cytoblasts
* P. 415.
INTRODUCTION. 27
and cells of plants precludes the possibility of our consider- ing them as the latter, while the appearance of a vitelline nucleus, transparent but molecular fluid, a chorion or shell, determines them as animal ova. It was shown to be impos- sible that these eggs had been deposited in the empty shell by other infusoria, or that they were the produce of some entozoon.
" 4th. That while it was impossible to determine whether the vague motions of Closterium were voluntary or not, yet the idea the author had formed of a suctorial apparatus, forbad his classing them with plants."
I confess I am unable to refer to any example in other Algae of terminal globules like those present in the Closteria, but neither can one be found amongst animals ; and if in some respects they have an analogy with organs belonging to the latter, in others they agree better with vegetable life. The contained granules seem to me to differ in no respect, except in position and uninterrupted motion, from other granules in the same frond, and, as I have already stated, I once saw the motion continue after their escape from the cell precisely as in other zoospores. Meyen observes that " the functions of these bodies is very difficult to determine, but they are to be found in very many Confervse, and are perhaps to be likened to the spermatic animalcules of plants."
The contraction of the internal membrane of the Closteria, or the expulsion of their contents on the application of iodine or other reagents, cannot be relied upon as a satisfactory test for determining their nature, for the blandest fluids will, in some cases, occasion violent action. If fresh water touches Griffithsia setacea, the joints burst and spirt out their con- tents ; and if it be applied to a species of Elachistea, the granular contents are instantly thrown into commotion. In certain conditions of the Closteria themselves, water will produce effects like those attributed to reagents. I have frequently witnessed that by the addition of water to speci- mens of Closteria, which had for some time been kept merely in a damp state, the frond has been ruptured, and the endo-
28 INTRODUCTION.
chrome has escaped with considerable force. This is espe- cially the case with Closterium Lunula ; and the same circum- stance occurs in most of the Desmidieae, although in none of the others so remarkably as in that genus. Mr. P. Grant has favoured me with an account of numerous experiments which he instituted to determine the effects of different sub- stances on the Desmidieae, Conjugatse, &c. From these it seems that the action of a reagent cannot be predicated with any certainty, and that the molecular motion is not affected by several strong poisons, whilst it yields to other substances less generally deleterious.
With regard to the " supposed ova," I fully agree with Meyen that " they are similar to the green corpuscles found in the cells of the Confervse," and, when both are removed from their cells, I am persuaded that it would be impossible to distinguish between them. That they contain amylum has been, with good reason, pointed out by Meyen as decisive against the notion that they are eggs.
The latest advocate of the animal nature of the Desmidiese is C. Eckhard, in his memoir ' on the Organization of the Polygastric Infusoria,' published in Weigmann's Archiv, part 3, 1846. With this memoir I am acquainted only through the medium of a translation by Dr. J. W. Griffiths in the * Annals of Natural History*.' It is apparently written for the purpose of confirming Ehrenberg's views, and accordingly defends his accuracy in every respect. So far as regards the Desmidieae, Eckhard notices only the Closteria, and he ad- vances nothing additional except an opinion that the trans- verse suture is a fissure or mouth. In order that both sides of the question may be compared, I extract his remarks, and merely point out that he has left unnoticed the facts on which botanists place their chief reliance : —
" The grounds for their being of animal nature are derived partly from their motion, partly from their organization. On the leaves of Ceratophyllum, I observed the manner in
* Vol. xviii. p. 433.
INTRODUCTION. 29
which several Closteria adhered elegantly by one extremity ; in about a quarter or half an hour many of them were situated in the same manner upon a higher part of the leaf: not a single animalcule was found on the side of the leaf, nor ad- herent longitudinally to it. They had evidently moved during the above time from the lower to the upper part of the leaf. If we observe their motions under the microscope they are not so rapid as those of many other polygastric in- fusoria, but the motion is always evidently animal. They swim, especially in summer, in the most varied directions, and I have frequently seen CI. acerosum and Lunula swim against the current when the water on the object-holder was flowing towards one side, whilst fragments of plants, various kinds of Spirogyra and Oscillatoria were carried away. It is difficult here to discover anything but animal motion ; to explain this however by electricity, as Turpin attempted, is unnatural, and not less absurd than that of the muscular fibre by the same natural agent by Strauss. But the rela- tions of the organization of the Closterina are likewise in favour of their animal nature. In illustration of this I shall confine myself to CI. acerosum. We see that the animal, which is expanded in the middle, is elongated symmetrically on each side. In the middle there is a transverse fissure, which probably serves for the admission of nourishment ; since, when this animal is kept for some time in coloured water, we perceive little accumulations of the colouring matters. At the extremities we see on each side a vesicle, in which minute granules (?) incessantly move. In other species there is moreover a small aperture ; it is situated more posteriorly, and is perhaps connected with the cell. Ehrenberg twice saw in this animalcule filaments (feet ?) pro- ject from it. Internally there are on each side two or four cords, and a row (in other kinds several) of granular bodies. In the species figured, I have so often seen the above change in relative position, that I have been compelled to wait until they again appeared in their original position in order to delineate them. All this is not plant-like ; and if the carapace
3€K INTRODUCTION.
of the Closterina should prove to be of a horny nature, as would appear to be the case from their becoming wrinkled when heated, they would be removed from the vegetable kingdom with still greater certainty."
Although at first sight it seems to indicate the contrary, the swarming of the zoospores or granules really affords a strong confirmation of the vegetable nature of the Desmidiese. This swarming has been noticed in the Algse by many emi- nent observers, and notwithstanding the extraordinary phae- nomena which it presents, no fact in their history is more firmly established. Hence J. G. Agardh, who so worthily emulates his father's fame, has been induced to apply the name of " Zoospermese" to one of his three primary divisions of the Algse. In this country the swarming has been witnessed by Mr. Borrer, the Rev. M. J. Berkeley, Mr. Hassall, and others. I have frequently seen it in Spharoplea crispa and Draparnaldia tenuis. A commotion arises within the cell as if all its contents were suddenly endued with life ; the disturbance increasing, the cell opens, when the zoospores hasten from their prison, and, apparently enjoying their newly-acquired liberty, dart about in every direction, until, tired of their sport, they at length resume a quiescent state*.
This description has such a marvellous character that the reader may suppose it is somewhat indebted to the imagi- nation, and I believe no one can witness the occurrence for the first time without being startled and almost led to doubt the evidence of sight. Such movements are so contrary to our ordinary experience of vegetable life, that we involun- tarily hesitate to admit their compatibility with it ; and on the continent many eminent naturalists, unable to find a satisfactory explanation, consider that in this stage the zoo- spores are really animals, and do not acquire their vegetable nature until a subsequent period. This opinion never ob- tained countenance in this country : yet a Berkeley did not
* The fullest details accessible to the English reader will be found in Mr. Harvey's excellent introduction to his ' Manual of British Algae,' and in the introduction to Hassall's ' British Freshwater Algae.'
INTRODUCTION. 31
esteem its refutation unworthy of his pen, and a Harvey thought it necessary to record his dissent from it and his behef that the phtienomenon must be regarded as a " strictly vegetable peculiarity." All that I have alluded to as hap- pening in the Algee occurs also in the Desmidieee ; but no similar motion has ever been observed in the contents of an animal after their escape from the individual, and I there- fore claim its presence in the Desmidieee as a strong pre- sumptive evidence in support of their vegetable nature.
Starch has been observed in the Desmidiese by many per- sons, and I am not aware that its occurrence is now denied by any one. I should therefore have supposed that it hardly required further proof, but as the subject is altogether un- noticed by most writers on the opposite side, it becomes necessary to bring it fully before the reader.
Meyen first directed attention to the presence of starch as a conclusive proof that the Desmidiese are Algae. He states that in several genera he has " distinctly seen that the large and small granules contained amylum, and were sometimes even entirely composed of it*," and that " in the month of May he had observed many specimens of Closterium in which the whole interior substance was granulated, and all the grains gave with iodine a beautiful blue colour, as is the case with starch, ivhich is not an animal product." I know not that Ehrenberg or his followers have ever repeated Meyen's experiments or taken the slightest notice of them, important as they are to the solution of the disputed ques- tion. In this country, Mr. Dalrymple at first failed to detect starch in the Closterise, but afterwards observed it in spe- cimens of Closterium (Penium) Digitus, which I sent him, and acknowledged its presence in the following terms : — " I have examined the specimens sent up, and in several I can detect the blue colour of the iodide of starch ; this is by no means however universal, some being merely stained yellowish- brown ; but in those instances there appears to be an absence
* See American Journal of Science and Arts, vol. xli. p. 298.
32 INTRODUCTION.
of granular matter, the fact of blue granules in some is how- ever decisive of the presence of starch." Mr. Dalrymple is so careful and accurate an observer, that I doubt not his failure was caused by the immature. state of the specimens on which he experimented, as he indeed subsequently allowed might have been the case.
Professor Bailey of the U.S. Military Academy, in an article on the American ' Desmidiacese'*, gives copious ex- tracts from Mr. Dalrymple's paper on the Closteria, accom- panied by his own remarks. He bears testimony to the general correctness of Mr. Dalrymple's observations, but with regard to those on the action of iodine, he says, "I cannot otherwise account for Mr. Dalrymple's statement, that iodine ' in no instance produced in the Closteria the violet or blue colour indicating starch,' than by supposing that the specimens he examined were not in the proper state to exhibit it. Meyen expressly states that it is ' at certain times, particularly in spring,' that the starch may be detected. I am able by conclusive experiments to con- firm Meyen's statement as to the presence of starch in these bodies. In specimens gathered in November I find no difficulty in producing the blue colour with tincture of iodine. Sometimes however the specimen becomes so opake by the action of this reagent, that the purple colour of the granules can only be detected after crushing the spe- cimen by means of the compressor. TJie characteristic colour of iodide of starch is then shown most distinctly. I have re- peatedly treated in this way Closterium Trabecula, as well as others, and have uniformly found that a portion of the in- terior takes the purplish colourf."
I have myself repeatedly noted the effects of iodine on many of the Desmidieae. In a young state the cells are filled with a green homogeneous fluid, which as the plant ap- proaches to maturity becomes granular. Scattered amongst
* American Journal of Science and Arts, vol. xli. p. 287. t Ibid, p. 301.
INTRODUCTION. 33
this minutely granular matter, larger granules, or rather vesicles, make their appearance. These Ehrenberg calls ova ; but I cannot perceive the slightest difference between them and the granules present in the higher Algse.
On applying diluted tincture of iodine to different species of the Desmidiese, the granules become very dark with a purplish tinge showing the presence of starch. When the tincture of iodine is used in its undiluted state, the colouring matter becomes nearly black and conceals the bluish tint ; in some specimens too this tint is hardly perceptible, whilst in others it is very apparent. In no instance have I found the presence of starch indicated unless granules were pre- sent, as the fluid colouring-matter always becomes brownish. The application of iodine to Conjugatee in different stages of growth was followed by a precisely similar result. In the young plant no starch was detected, but the colouring matter changed to an orange-brow^n. On the other hand, in the conjugating filaments the granules became blue, and the sporangia especially acquired the very dark colour observed in the Desmidiese, and did not exhibit the iodide of starch until they were crushed.
Professor Bailey's testimony is the more satisfactory be- cause it is not the evidence of a partisan, but the admission of one inclined to regard the Desmidiese as pertaining to the animal kingdom. Although he does not " consider the pre- sence of starch in these bodies as conclusive evidence that they are plants," yet as a professor of chemistry he is aware that starch is not an animal product, and he suggests there- fore, with some ingenuity, "Is it not possible that they are animals which feed, wholly or in part, on amylaceous matter extracted from the aquatic plants among which they live ? if so, the detection of starch in their stomachs is not sur- prising."
In the young cell there is no starch, but after its first ap- pearance it continues to increase and is most plentiful in the sporangium ; facts quite incompatible with Professor Bailey's
D
34 INTRODUCTION.
suggestion, but strictly analogous with its presence in the Conjugatae, and indeed in plants in general, for it is well known that starch is often most abundantly produced in the seed.
Of all the facts which indicate the vegetable nature of the Desmidicce, this is undoubtedly the most important, since it is the most easily subjected to the test of experiment. The swarming of the zoospores is seen only now and then, and it is not always easy to trace the process of coupling ; but every person can apply the test for starch, and needs only to bear in mind that unless granular matter be present there is no starch*.
The conjugation of the fronds in this family supphes an equally striking fact in proof that it belongs to the vegetable kingdom. I have already mentioned that we have amongst the Algae many examples of the junction of two individuals!, and the commingling and union of their entire contents into a seed- like body for the purpose of reproduction. The case of the Conjugatse is well known, and Mr. Hassall has proved that the same phcenomenon takes place in other genera.
* After the diluted tincture of iodine is applied, the free iodine should be removed by the aid of heat, occasionally adding a little water to facilitate its^ removal. This in great measure removes the brownish stain which obscures the purple tint, and then on applying the highest powers of the microscope, the peculiar colour of the iodide can in general be easily perceived.
t So far as relates to the formation of the sporangium, each joint in the Conjugatae must be considered a distinct individual. On the contrary, in the Desmidiese, each frond resulting from division is merely a portion taken from the original one, and like a graft or slip from an apple, a willow, or a car- nation, retains every accidental peculiarity of the variety from which it parted. Thus one pool may abound with individuals of Staurastrum de- jectum or Arthrodesmus incus, having the mucro curved outwards ; in a neigh- bouring pool every specimen may have it curved inwards ; and in another it may be straight. The cause of the similarity in each pool, no doubt is, that its plants are offsets from a few primary fronds. The above fact, I must further remark, often renders it very difficult to decide whether a particular form be really a distinct species or merely a variety, since its abundance will not suffice to establish its claim to the rank of a species.
INTRODUCTION.
In the Desmidiccie, in like manner, a bag or cell forms be- tween two individuals, and the entire contents of both these (or indeed of four, if we regard the fronds as binate) pass out and unite together to form one reproductive body, which becoming detached, leaves the parent corpuscles altogether empty. Such an occurrence is, I believe, not only unknown amongst ani- mals, but is contrary to all our notions of animal propagation.
Among the Conjugatae, Tyndaridea has an orbicular spo- rangium, Staurocarpus a cruciform or quadrate one ; in Zygnema it is formed within one of the coupling cells, and in Mougeotia it is situated in the connecting tube. The Des- midiese present us with corresponding variations. Their sporangia are generally orbicular, but Staurastrum, Tetme- morus, Closterium and Penium afford examples of cruciform and quadrate ones : and although the reproductive body is usually contained in the connecting tube, yet in Didy- moprium Grevillii it is placed in one of the conjugating cells. Lastly, we have the Didymoprium Borreri, in which the con- jugated filaments form a kind of network in the same man- ner as in Mougeotia.
That the Desmidiese resist decomposition, exhale oxygen on exposure to the sun, preserve the purity of the water containing them, and when burnt do not emit the peculiar odour usually so characteristic of animal combustion^ are other facts respecting this family, which taken singly might have less value, but in their combination furnish a most im- portant support to the arguments already adduced.
On the foregoing statements I rest the claim of the Des- midiese to be considered Algse ; and I confidently appeal to any impartial person whether they do not at least require to be answered before the conclusion which I have drawn can be rejected. But on consulting the works of those who pro- fess to prove the contrary, we find that the important facts which I have here investigated are either altogether over- looked, or passed by without an attempt to controvert them. For my own part I believe them to be unanswerable.
I have pointed out that the swarming of the granules
D 2
36 INTRODUCTION.
occurs in acknowledged Algae as well as in the Desmidiese ; and that nothing which can fairly be compared with it occurs in the animal kingdom. Can either of these assertions be disproved? Again, it has been seen that starch is abun- dantly produced in this family. Can a single example be referred to where it is an animal product ? I have shown that the reproductive body is formed in a manner well known amongst the Algse, but never detected in animals. Until these facts have been denied, or the arguments deduced from them refuted, I shall presume that the claim of the Des- midieae to be considered vegetables is firmly established*.
The Desmidiese I regard then as Algse, allied on the one side to the Conjugatse by similarity of reproduction, and on the other to the Palmellese, by the usually complete transverse division and by the presence of gelatine. Indeed the relation to the latter is so intimate, that it is difficult to say to which
* Since the above was written, a friend has furnished me with the trans- lation of a passage from a recent work of Meneghini, which is so appropriate in support of my views that I gladly introduce it here : —
" The Closteria and the Desmidiece are universally plants and not animals. In the actual state of science we are obliged to admit this proposition. The organic structure, the physiological phsenomena, the history of their develop- ment, their chemical composition, manifest in these brings a perfect corre- spondence with others, which, under all their aspects, are comprised in the abstract idea of a plant. On the other hand, what they present in common with those beings evidently animal is but an appearance, or at most a simi- larity of external form. Ehrenberg was deceived by this appearance, and, guided by this fallacious resemblance, thought he discovered even in the Desmidiese the same organic peculiarities which prove the animality of other beings. What must we infer from this ? That even the most accurate ob- server and man of genius may err. 7'his can never diminish his merit or render less important the services which he has rendered to science. The loss will fall only on those who, averse to the fatigue of observing, content themselves with the authority of the master, and embrace without distinction his real discoveries and his errors. Thank Heaven, the epoch of authority is passed, and whoever submits to its yoke may be allowed to err, because science will not advance the less for him, and may even derive advantage from those very errors. From the study of the Desmidiese, and from their being brought into comparison with animals, valuable notions upon the in- timate structure of vegetables have already been derived." — SuUa Animalita della Diatomee, p. 172.
INTRODUCTION. 37
family some genera belong. Thus Merismopaedia, placed by Meneghini and Kiitzing in the Desmidiese, I believe, with. JVJeyen, to belong properly to the Palmellete. On the other hand, Cylindrocystis, placed in the latter by Meneghini and Brebisson, has been rightly removed to the Desmidieee by Kiitzing and Hassall. Brebisson's discovery of conjugated specimens of Coccochloris protuberans and Cocc. rubescens brings to our notice another link connecting these families, whilst some species of Scenedesmus may be allowed to have an almost equal claim to rank with either.
Respecting the uses of the Desmidiese little is known. Doubtless, in common with other aquatic vegetables, they tend to preserve the purity of the water in which they live,, and Mr. Williamson has ascertained that to a great extent they furnish food for the bivalved mollusks which inhabit fresh waters.
As the Desmidiese are unattached and very minute, they are rarely gathered in streams : nevertheless interesting species may occasionally be obtained where the current is so sluggish as to permit the thin retaining mucus to elude its force. In small shallow pools that do not dry up in summer they are most abundant ; hence pools in boggy places are generally productive.
The Desmidieae prefer an open country. They abound on moors and in exposed places, but are rarely found in shady woods or in deep ditches. To search for them in turbid waters is useless : such situations are the haunts of animals, not the habitats of the Desmidiese, and the waters in which the latter are present are always clear to the very bottom.
M. de Brebisson informs me that in France, calcareous districts, which are so favourable to the Diatomacese, are very unproductive of Desmidiese. 1 have myself had no opportunity of ascertaining whether the same fact obtains in England. Mr. Thwaites and Mr. Jenner have indeed fur- nished me with fewer habitats from calcareous soils, but the less frequent occurrence of small pools and bogs in such di- stricts may perhaps partly explain the deficiency.
38 INTRODUCTION.
Ill the water the filamentous species resemble the Zyg- nemata, but their green colour is generally paler and more opake. They often occur in considerable quantity, and, notwithstanding their fragility, can generally be removed by the hand in the usual manner. When they are much dif- fused in the w^ater, I take a piece of linen about the size of a pocket-handkerchief, lay it on the ground in the form of a bag, and then, by the aid of a tin box, scoop up the water and strain it through the bag, repeating the process as often as may be required. The larger species of Euastrum, Mi- crasterias, Closterium, &c., are generally situated at the bottom of the pool, either spread out as a thin gelatinous stratum, or collected into finger-like tufts. If the finger be gently passed beneath them they will rise to the surface in little masses, and with care may be removed and strained through the linen as above described. At first nothing ap- pears on the linen except a mere stain or a little dirt ; but by repeated fillings-up and strainings a considerable quantity will be obtained. If not very gelatinous, the water passes freely through the linen, from which the specimen can be scraped with a knife and transferred to a smaller piece ; but in many species the fluid at length does not admit of being strained off without the employment of such force as would cause the fronds also to pass through, and in this case it should be poured into bottles until they are quite full. But many species of Staurastrum, Pediastrum, &c. usually form a greenish or dirty cloud upon the stems and leaves of the filiform aquatic plants, and to collect them requires more care than is necessary in the former instances. In this state the slightest touch will break up the whole mass and di- sperse it through the water. I would recommend the fol- lowing method as the best-adapted for securing them. Let the hand be passed very gently into the water and beneath the cloud, the palm upwards and the fingers apart, so that the leaves or stem of the invested plant may lie between them and as near the palm as possible ; then close the fingers, and keeping the hand in the same position, but concave, draw it
INTRODUCTION. 39
cautiously towards the surface, when, if the plant has been allowed to slip easily and with an equable movement through the fingers, the Desmidiese, in this way brushed off, will be found lying in the palm. The greatest difficulty is in with- drawing the hand from the surface of the water, and probably but little will be retained at first ; practice, however, will soon render the operation easy and successful. The contents of the hand should be transferred at once either to a bottle or, in case much water has been taken up, into the box, which must be close at hand, and when this is full it can be emptied on the linen as before. But in this case the linen should be pressed gently and a portion only of the water expelled, the remainder being poured into the bottle, and the process re- peated as often as necessary.
Sporangia are collected more frequently by the last than the preceding methods. When carried home, the bottles will apparently contain only foul water, but if it remain un- disturbed for a few hours, the Desmidiese will sink to the bottom, and most of the water may then be poured off. If a little fresh water be added occasionally to replace what has been drawn off, and the bottle be exposed to the light of the sun, the Desmidiese will remain unaltered for a longtime. I have now before me some specimens of Euastrum insigne, the fronds of which are in as good condition as when I gathered them at Dolgelly five months ago.
Mr. Thwaites's kindness has enabled me to render this Introduction more complete by the following account of two methods adopted by him in mounting minute Algse for the microscope, which he has drawn up at my request. The remarks which I have appended have been derived from other sources, as well as from my own experience : —
" In making preparations of the Algse for the microscope, there are two things which principally require to be attended to : first, to obtain a fluid which shall preserve the plant as little altered as possible from its appearance when living ; and secondly, to adopt the best means for preventing the escape of this fluid after the object has been mounted in it.
40 INTRODUCTION.
With respect to the first point, the fluid which I have found to answer best is made in the following way : — To sixteen parts of distilled ivater add one part of rectified spirits of wine and a few drops of creosote sufficient to saturate it ; stir in a small quantity of prepared chalk and then filter : with this fluid mix an equal measure of camphor -water (water satu- rated with camphor), and before using strain off through a piece of fine linen.
" This fluid I do not find to alter the appearance of the endochrome of Algse more than distilled water alone does after some time, and there is certainly less probability of con- fervoid filaments making their appearance in the prepa- rations ; and there would seem to be nothing to prevent such a growth from taking place when the object is mounted in water only, provided a germ of one of these minute plants happen to be present, as well as a small quantity of free carbonic acid.
"Fluids containing a larger quantity of spirits of wine, and consequently of creosote also, than the one of which I have given the formula, produce a greater change in the appearance of the endochrome. I at one time thought that by increasing the density of the mounting fluid, the endochrome of the plant might be less disturbed, and I dissolved a small quantity of sugar in the fluid ; but this made the cell-mem- brane too transparent, and rendered completely invisible the gelatinous sheath with which many species of Algae are furnished.
" I now proceed to describe my method of making cells in which to mount preparations of Algse. Some objects re- quire very shallow and others somewhat deeper cells. The former may be made with a mixture of japanners' gold-size and litharge, to which (if a dark colour is preferred) a small quantity of lamp-black can be added. These materials should be rubbed up together with a painter's muller, and the mixture laid on the slips of glass with a camel-hair pencil as expeditiously as possible, since it quickly becomes hard ; so that it is expedient to make but a small quantity at
INTRODUCTION, 41
a time. For the deeper cells marine-glue answers extremely well, provided it is not too soft. It must be melted and dropped upon the slip of glass, then flattened, whilst warm, with a piece of wet glass, and what is superfluous cut away with a knife, so as to leave only the walls of the cell ; these, if they have become loosened, may be made firm again by warming the under surface of the slip of glass. The surface of the cells must be made quite flat, which can be easily done by rubbing them upon a wet piece of smooth marble covered with the finest emery powder.
" When about to mount a preparation, a very thin layer of gold-size must be put upon the wall of the cell as well as on the edge of the piece of thin glass which is to cover it ; before this is quite dry, the fluid with the object is to be put into the cell, and the cover of thin glass slowly laid upon it, beginning at one end : gentle pressure must then be used to squeeze out the superfluous fluid, and, after carefully wiping the slide dry, a thin coat of gold-size should be applied round the edge of the cell, and a second coat so soon as the first is dry : a thin coat or two of black sealing-wax varnish may then be put on with advantage, in order to prevent effectually the admission of air into the cell or the escape of fluid out of it.
*' I at first mounted objects for the microscope without enclosing them in a cell previously prepared for their recep- tion, but merely by laying them on the slip of glass with a drop of the fluid, and then covering them up with a piece of thin glass or talc, and afterwards surrounding the latter with a border of thick gold-size, in order to prevent the evapo- ration of the enclosed fluid. Preparations so made will fre- quently last some considerable time ; but eventually the contraction, as it becomes dry, of the outer surface of gold- size forces the remainder, which still continues soft, between the two glasses, and the mounted object is thus injured. I found the same thing frequently to occur when the cells were made of gold-size only without the litharge ; but this
42 INTRODUCTION.
inconvenience seems to be completely obviated by the plan I have recommended above.
" I would remark that the gold-size employed should be of the consistence of treacle ; when purchased it is usually too fluid, and should be exposed for some time in an open vessel, a process which renders it fit for use."
Mr. Sidebotham also has favoured me with directions for mounting the Desmidiece. His method is nearly similar to that employed by Mr. Thwaites, but when the last coat of varnish is nearly dry, he applies a fine bronze with a camel- hair pencil. This not only has a neat effect, but prevents the risk of adhesion consequent on the softening of the var- nish in warm weather. Mr. Sidebotham uses distilled water as the mounting fluid, but although his specimens retain the green colour of the endochrome better than any other I have seen, yet, for the reason assigned by Mr. Thwaites, I doubt whether such a mode is suitable for their permanent preser- vation.
Mr. Thwaites' fluid is superior to camphorated- water and various other liquids which I have tried ; but as it requires more time for its preparation than may be at all times con- venient, I find the following the best substitute : —
Bay -salt and alum, one grain each, dissolved in an ounce of distilled water.
Goadby's solution acts too powerfully on freshwater Algae, and corrosive sublimate injures the specimens.
In mounting the Desmidieee great attention is necessary to exclude air-bubbles, which cannot be avoided unless the fluid completely fills the cell ; and also not to use too much fluid, as in this case the smaller species will often be washed away on the escape of the superfluous portion.
As the cells cannot be sealed whilst any moisture remains on their edge, it should be removed by blotting-paper, which is preferable to any other mode.
The thin glass manufactured for the purpose is preferable to talc for covering the specimen, and should always be used
INTRODUCTION. 43
by those who possess an achromatic microscope ; but with a simple instrument the triplet can be used only when talc is the covering.
Specimens are frequently spoiled by the intrusion of the gold-size into the cell. Experience will best teach how this accident is to be avoided ; attention however to the following particulars will assist the inexperienced. The cells should be prepared some days before they are used, in order that their walls may become firm. When the cell is closed the brush should be passed round the edge of the cover, with just sufficient size to prevent the admission of air into the cell ; and upon the operator's care in this respect will depend his success. If too little size be used the air finds admission, and if much be put on, or if the cell be not completely filled with fluid, the size will enter and spoil the specimen. When the first layer of size is quite dry, he should proceed as di- rected by Mr. Thwaites.
Mr. Topping has kindly sent me a description of his method of preparing cells for mounting microscopic objects. He uses strips of plate-glass of an uniform size (three inches by one), and marks on them the size of the cell, by taking two thin pieces of mahogany of the size of the glass, each having a hole (circular, oval or square, as may be desired) cut in its centre, the smaller corresponding with the inner margin of the cell, and the larger with the outer. These, when laid over the glass, offer a ready means of tracing with a diamond the space around the cell, which must then be filled up with japan. This is next hardened by placing the glasses in an oven, the heat of which should be raised gra- dually, as otherwise the japan will blister ; but if care be taken in this part of the process the cells will resist the action of proof spirit.
The fluid which Mr. Topping has used for mounting con- sists of one ounce of rectified spirit to five ounces of distilled water, which he thinks superior to any other combination. To preserve delicate colours however, he prefers to use a so- lution of acetate of alumina — one ounce of the acetate to four
44 INTRODUCTION.
ounces of distilled water. Of other solutions, he says that they " tend to destroy the colouring-matter of delicate objects, and ultimately spoil them by rendering them opake*."
To those who will read a book on this subject, it is quite unnecessary to enter upon a formal vindication of the study of the lower tribes of organized life. 1 shall content myself with the observation that, whilst this study is not wanting in those qualities which recommend the other branches of Natural History as a means of intellectual improvement, it has a peculiar claim on account of the light which it reflects on the ultimate organization of living bodies in general. Physiologists have of late pursued the investigation of the structure and development of cells, both animal and vege- table, with the greatest zeal ; and with good reason, since it is obviously most desirable that we should thoroughly un- derstand these elements of organization before we attempt to explain its more complicated arrangements. For the attain- ment of so important an object, the Desmidiese furnish the most valuable assistance. If the view which I have taken be correct, their frond, in most of the genera at least, con- sists of a single cell, which, although it is certainly more complex than cells in general, enables us to trace its own history with ease and certainty, and reveals to us that of forms still more simple.
It may suffice thus briefly to show the utility of such in- quiries ; but the improvements which the microscope has received in modern times may well suggest a wider applica- tion of the language in which the illustrious Ray vindicated his favourite pursuits f.
* Whilst my best thanks are due to Mr. Topping for this account of his mode of preparing the cells, I must observe that the neat execution of them re- quires more skill and leisure than most persons possess, and therefore presume I shall render an acceptable service to my readers by mentioning that cells of an)'^ shape or size that may be required, and also the thin glass necessary for closing them, are supplied by Mr. Topping. In justice to Mr. T., whose cells I have used extensively, I must bear testimony to their beauty and utility. Misaddress is No. 1, York Place, Pentonville, London.
-j- " Non deerit qui me vanse curiositatis arguat, qu6d res adeo viles et ab-
INTRODUCTION. 45
What the Allwise did not disdain to create cannot be un- worthy of our notice ; and if in the minute Desmidiese, so long concealed from the unassisted eye, we have been at length enabled to recognize objects as carefully organized as the bulky elephant or the majestic oak, and as happily adapted to their position in nature, possessing too an eco- nomy whose laws are no less constant and regular, shall we not gladly examine this fresh evidence of an Almighty hand, as distinctly impressed on them as on the rest of his crea- tion?
" To Him no high, no low, no great, no small ; He fills, He bounds, connects and equals all."
jectas, nullius in vita usus, indagaverim, iisque describendis tantum temporis et operse impenderim. Cui respondeo. Quod Dei opera sunt in quibus con- templandis memet exerceo ; quod Divinse Artis et Potentise efFecta, quibus exquirendis subsecivas horas addico ; quod Ille me in hunc mundum intro- duxerit, tam inexplicabili rerum varietate instructum et ornatum ; quod oculis, quos mihi contulit, ea videnda, animo consideranda objecerit. In Dei ergo contumeliam redundat, quod haec, quae eum creasse negare non audes, super- vacua et inutilia esse affirmes." — Hist. Plant, v. 3. praef. p. ii.
SYNOPSIS OF THE GENERA.
Fam. DESMIDIE^.
Freshwater, figured, mucous and microscopic Algae, of a green colour. Transverse division mostly complete, but in some genera incomplete. Cells or joints of two symmetrical valves, the junction always marked by the division of the endochrome, often also by a constriction. Sporangia formed by the coupling of the cells and union of their contents.
* Plant an elongated jointed filament. Sporangia orbicular, smooth.
1 . Hyalotheca. Filament cylindrical.
2. Didyrnoprium. Filament cylindrical or subcyliudrical ; joints with
two opposite bidentate projections.
3. Desmidium. Filament triangular or quadrangular ; joints connected
by a thickened border.
4. Aptogonum. Filament triangular or plane, with foramina between
the joints.
5. Spbserozosma. Filament plane, margins incised or sinuated ; joints
with junction glands.
** Frond simple from complete transverse division, distinctly con- stricted at the junction of the segments, which are seldom longer than broad. Sporangia spinous or tuberculated, rarely if ever smooth.
6. Micrasterias. Lobes of the segments incised or bidentate.
7. Euastrum. Segments sinuated, generally notched at the end, and
with inflated protuberances.
50 SYNOPSIS OF THE GENERA.
8. Cosmarium. Segments in front view neither notched nor sinuated,
in end view eUiptic, circular or cruciform.
9. Xauthidium. Segments compressed, entire and spinous.
10. Arthrodesmus. Segments compressed, and having only two spines or mucros.
1 1 . Staurastrum. End view angular, radiate, or with elongated pro- cesses, which are never geminate.
1 2. Didymocladon. Segments angular, each angle having two processes, one inferior, and parallel with the similar one of the other segment, the other superior and divergent.
*** Frond simple from complete transverse division, generally much- elongated, never spinous, frequently not constricted at the centre. Sporangia smooth.
13. Tetmemorus. Frond straight, constricted at the centre and notched
at the ends.
14. Penium. Frond straight, scarcely constricted at the centre.
15. Docidium. Frond straight, much-elongated, constricted at the centre, truncate at the ends.
16. Closterium. Frond crescent-shaped or arcuate, not constricted at the centre.
17. Spirotsenia. Frond straight, not constricted at the centre ; endo- chrome spirally twisted.
**** Cells elongated, entire, fasciculated.
18. Ankistrodesmus. Cells aggregated into faggot-like bundles.
***** Frond composed of few cells, definite in number, and not forming a filament. (Sporangia unknown.)
19. Pediastrum. Cells arranged in the form of a flattened star; their outer margin bidentate.
20. Scenedesmus. Cells oblong or fusiform, entire, placed side by side ia a single row, but during division in two rows.
BRITISH DESMIDIE^.
* Plant an elongated jointed filament. Sporangia orbicular, smooth.
1. HYALOTHECA, Ehr.
Filament elongated, cylindrical, very gelatinous ; Joints having either a slight constriction which produces a crenate appearance, or a grooved rim at one end which forms a bifid projection on each side. End view circular.
The filaments are cylindrical, simple, jointed, invested with a broad gelatinous sheath, and very fragile in one species but not so in the other. Either a groove passes round each joint, giving a crenate appearance to the margins of the filament and dividing the endo- chrome into two portions, or else a grooved rim at one extremity of the joint appears on each side like a bifid process.
A transverse view shows a radiate endochrome in one species ; but I have been unable to determine whether this occurs in the other, on account of its imperfect fragility.
The cylindrical filament distinguishes this genus from Desmidium and Spharozosma. It has no angular projections, is not twisted, and has always the same apparent breadth, and consequently in all these respects differs from Didymoprium.
I. H. dissiliens (Smith) ; filament fragile, crenate; a shallow groove round each joint dividing the endochrome into two portions.
Conferva dissiliens. Smith, Eyxg. ^o^ t. 2464. (1812) (not Dillw.). Desmidium mueosum, 13reb. Aly. Fat. p. 65. t. 2 (1835). Menegli. St/nop.
Desmid. in Litincea 1840, p. 204. Ralfs in A?mals of Nat. Hist. v. 11,
p. 374. t. 8. f. 2. Besmidium limbatum, Chauv. Alg.de la Norm. f. 6. (1836), according to
Meneshini.
52 BRITISH DESMIDIE^E.
Gloeoprium dissiliens, Berk, in Annals of Nat. Hist, v. 16. p. 11 (1845).
Jenner, Fl. of Tunbridge Wells, p. 192. Hassall, Brit. Freshwater
Algce, p. 346. t. 83. f. 3. Hyalotheca mucosa, Kiitz. Phycologia Germanica, p. 140? (1845). Hyalotheca dissiliens, Breb. in lit. (1846).
Common. Henfield, Sussex ; and Cwm Bychan, North Wales, Mr. Borrer. Swansea ; Dolgelley ; Bedgelert ; Penzance, &c., J. R. Hampshire and many stations in Sussex, Kent and Surrey, Mr. Jenner. Essex and Herts, Mr. Hassall. Ayrshire, Rev. D. Landsborough. Aberdeen, Dr. Dickie and Mr. P. Grant. Bandon, Professor Allman. JLerr j, Mr. Andrews. Ambleside, Mr. Sidebotham. Yate near Bristol, Mr. Broome. Stoke Hill near Wells, Mr. Thwaites. Rochdale, Mr. Coates. Manchester, Mr. Williamson.
Germany, Kutzing. Falaise, Br^bisson. West Point, New York, Pro- fessor Bailey.
Filaments mucous, adhering firmly to paper. The joints are usually broader than long, and as each has a shallow groove passing round it, it re- sembles a small pulley -wheel, and the filament acquires a crenate appearance ; the crenatures are generally very shallow, sometimes nearly obsolete, but I have occasionally seen them deeper, when the plant looks more like the figure in ' Eng. Bot. ;' at all times they may be detected on a careful examination with the higher powers of the microscope. The endochrome is divided into two portions by this constriction, and there is scarcely any depression between the joints.
The mucous sheath is easily observed, and on each side of the filament is nearly as broad as the central coloured portion. The sheath and filament are alike cylindrical.
If kept in water for a few days the plant separates into single joints, each of which has a perfect mucous covering. In the Desmidiese in general the filaments separate mto single joints with a facility proportioned to the greater development of the sheath ; but Hyalotheca mucosa in this, as in other re- spects, deviates from the rest of the group. The breaking up takes place more speedily in the present plant, in Didymoprium Grevillii and Sphfsro- zosma vertebratum, than in Didymoprium Borreri or in the genus Desmidium. This circumstance seems to depend upon the elasticity of the mucous covering of the joint. This elasticity is proved by its becoming longer than the joint immediately upon separation, and hence into whatever number of pieces a filament may be broken, the ends of each portion are as perfectly covered as the original end of the filament itself, and with regard to each particular joint the result is the same.
The transverse view is circular, and shows a mucous border of the same form. In this aspect the endochrome is generally disposed in a stellate man- ner, with six or seven rays, and frequently has a colourless central spot.
Foreign specimens of " Desmidium mucosum," given me by the Rev. M. J. Berkeley, agree in all points with the above description.
Hyalotheca dissiliens frequently occurs in considerable quantities, unmixed with other Algae. WTien young it agrees in appearance with many of the Conjugatse, but it may be distinguished by its fragility. It soon becomes of a pale opake green, and is then even more fragile than before.
BRITISH DESMIDIE.E. 53
Although I had seen sporangia of H. dissiliens at Penzance, I was unable to determme to what plant they belonged until Mr. Jeiuier sent them from Sussex and suggested that they were its conjugated state. At first the diffi- culty I experienced in recognizing the original cells in their altered condition induced me to hesitate in admittmg the correctness of his opinion. But having subsequently gathered this species in all stages near Dolgelley, I have traced its changes, with Mr. Jemier's assistance, and satisfied my doubts.
The filaments separate into single joints, which couple by tubes ; so far the manner of conjugation is similar to the examples I had previously seen in Staurastnun and Tetmemorus, but in those genera the segments of the cell are completely divided by the growth of the newly-formed portion ; in the present case the cells separate only on the sides opposed to each other. In the cleft is formed the new portion, the enlargement of which, after it has become the comiecting tube, by causing the cell to gape, produces a notch-like appearance on the outer margin. The process would be more evident if the similar texture of the old and new parts did not render it difficult at first sight to detect the joint in its altered form ; and the difficulty is increased, as the coupling usually takes place in a crossed or twisted position, which thus still farther disguises the joints.
The sporangium, which is circular, is situated within the connecting tube, and the empty joints are permanently attached to it.
I have been unable to determme, by my own observation, whether the mu- cous covering remains on the conjugated cells, but Mr. Jenner informs me that in some instances he has observed it, and indeed that its presence led him to the identification of the plant. As in most instances, however, it is either wanting or very obscure, I have thought it advisable to omit it in the figures of the sporangia, and merely to notice its occasional occurrence.
Sporangia have been gathered also by Mr. Thwaites, Dr. Dickie, Mr. Broome, and Mr. Sidebotham ; and M. de Brebisson informs me that he has met with them in France.
Length of joint from -aroT ^^ Tstt ^^ ^^ ^^^^ > breadth of filament from YFoT ^^ TsT ; breadth of sheath from -g-Lj- to g^y • Diameter of sporangium -g^.
Tab. I. f. 1. a, h. portions of mature filaments ; c. portion of a dividing fila- ment ; d, empty joint ; e, f. transverse view ; g. cells conjugating ; h, i. sporangia.
2. H. mucosa (Mert.) ; filament scarcely fragile ; joints not constricted, but having at one of the ends a minute bidentate projection on each margin, the adjoining end of the next joint being similar.
Conferva mucosa, Mert. Dillw. £rit. Conf. t. B. (1809). Hook. Br. Fl.
V. 2. p. 351. Harv. 5r. ^/^. p. 127. Hyalotheca mucosa, Ehr. Kurse Nachricht iiber 2/4 seit dem Abschluss der
Tafeln des grosser n Infusorienwerkes ? (1840). Gloeoprium mucosum, Ralfs, Annals of Nat. Hist. v. 16. p. 11. t. 3. f. 6.
(1845) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 165. t. 18. Jenner,
Fl. of Tunbridge Wells, p. 192. Hass. Br. Freshwater Algce, p. 346.
t. 83. f. 5. Hyalotheca Mertensii, Br^isson in lit. (1846).
e2
54 BRITISH DESMIDIE.^i:.
Ill shallow pools and gently-flowing streams ; most {)Ientiful in the autumn. Gantry, 3Iiss Hn f chins. Appin, Cupt. Carmichael. .Trentishoe, Devonshire ; Penzance ; and Dolgelley, J. R. Herts and Essex, Mr. HassctU. Chiltington Common, near Pulborough, Sussex ; Ashdown Forest ; and in the peat-bog at Fisher's Castle, near Tunbridge Wells, JSL'. Jenner. Near Aberdeen, Mr. P. Grant.
Falaise, France ; Brebisson.
Filaments elongated, very gelatinous, of a pale translucent green ; not fra- gile. Under the microscope the joints are generally about equal in length and breadth, and the endochrome forms a single irregular patch. The joints are not constricted, but at one end they have on each margin a minute bidentate projection : as the similar ones of the next joint are at its adjoining extremity, these projections occur only near the alternate dissepiments. When however the joint is elongated, preparatory to the formation of two joints, the endo- chrome is divided into two portions, and then these projections are present at both ends, the next joint undergoing a similar change. These projections are extremely minute, and can be detected only by employing the highest powers of the microscope ; and even then are liable to be overlooked, if not carefully sought for. I examined many specimens of this plant in 1841, but did not perceive these curious protuberances until the following year. I believe they are really formed by a grooved rim round the end of the joint, because how- ever the filaments may be moved, they are equally apparent ; whereas if they were real processes, as in Didymoprium, they would be sometimes either en- tirely concealed or rendered less distinct ; they can also be traced like a trans- verse band across the empty cell.
The filaments have a very broad mucous sheath, which from its gi'eat breadth and absence of colour is not easily discerned ; it is more evident when a specimen is dried on talc or glass, as the margins are then generally percep- tible. Wlien first gathered the filaments are very distinct, frequently parallel and subdistant even to the naked eye : this depends on the great breadth of their mucous sheaths, which prevents the coloured filaments from coming into contact. By this character H. mucosa may in general be known, even without the aid of a microscope. The same circumstance occurs in young plants of H. dissiliens, but is less remarkable, as its mucous sheath is not more than half as broad.
Under a low power of the microscope, H. mucosa has considerable resem- blance to H. dissiliens, vdth which it is probably not unfrequently confounded. But they may always be distinguished, even without the aid of a microscope. //. dissiliens is extremely fragile, and will break into pieces if a small portion be placed on the hand and the finger gently passed over it ; this plant, on the contrary, will not break if it be taken out of the water and allowed to hang dowi^ in long strings. It always has a clear translucent appearance ; but H. dissiliens, except when very young, is of an opake green. H. dissiliens, if kept in water for a few days, spontaneously separates into single joints ; //. mucosa, although treated in the same manner for weeks, did not separate into fragments sufficiently small to enable me to obtam a satisfactory transverse view. At length, however, I was more fortunate. When kept in water the
BRITISH DESMIDIE.E. 55
mucous sheath is partially dissolved, aud interferes with the examination of the joints, but by repeatedly changing the water I succeeded in procuring many single joints. The transverse view was circular, and when the cell was empty the border appeared decidedly striated. The endochrome had some tendency to a radiate form, but the treatment to which the filaments had been subjected prevented me from forming any certain conclusion as to its dispo- sition in the recent plant.
Under the microscope H. mucosa may be known from H. dissiliens by its joints never appearing crenate, and by its endochrome being almost always in a single patch, or by the greater length of the joints if the endochrome is bi- partite. Its mucous sheath is with difficulty detected, and when seen will be found to extend on each side twice the breadth of the coloured filament ; whereas in H. dissiliens the mucous sheath is, except in old specimens, de- tected without difficulty.
The joints seem to be in pairs ; a single one is consequently unsymmetrical.
H, inucosa agrees with the other Desmidiese in its capability of being kept a long time without midergoing decomposition.
This plant differs in many respects from the other Desmidiese ; indeed so much so, that I had some doubts whether it would be correctly placed in this family ; but as the Rev. M.J. Berkeley, as well as every other algological friend whose opinion I have solicited, considers that its place must be in the same genus vdth the preceding species, I have described it here.
I was first indebted to Mr. Hassall for the information that the plant under consideration is the Conferva mucosa, Dillw., as also for an opportunity of examinmg a foreign specimen under that name from the herbarium of Dr. Gre- ville. I have since been enabled to compare our plant with a portion of an Irish specimen of Conferva mucosa presented to me by Mr. Borrer, who re- ceived it from Sir W. J. Hooker. From the latter I learn that this was an original specimen from Miss Hutchins. Sir W. J. Hooker has also presented me with an Appin specimen, collected by Capt. Carmichael. All these are identical with the present plant.
Length of joint from y^Vs" ^^ TiVo^ ^^ ^^^ ^i^*^'^ 5 breadth of filament yjVo ^^ XTXT '■> breadth of sheath xhr-
Tab. I. f. 2. a. portion of a filament ; b. empty joints ; c, d. transverse views.
2. DIDYMOPRIUM, Kutz.
Filament elongated, gelatinous, fragile, regularly twisted, cylindrical, with a bidentate process or angle on each side oiXho. joint.
The filaments are elongated, simple, jointed, gelatinous and very fragile, and finally separate into single joints; each joint has two op- posite bidentate angles or processes. Hence the margins of the fila- ment are crenate ; and as it is regularly twisted, it not only appears
56 BRITISH DESMIDIE/E.
of unequal breadth, but the form of its joints also varies, as more or less of the angles is seen at the margin ; in short, as they are at one time fully visible, and at length entirely disappear.
In a transverse view the joints are circular or broadly elliptic, with two minute opposite projections which are formed by the angles. The endochrome is radiate ; its rays from four to seven.
Conjugated specimens of both species have been observed, and possess much interest from their being the representatives in this family of analogous states in some of the Conjugatse.
Didymoprium differs from Desmidium in having only two angles ; in a transverse view also the number of rays of the endochrome does not depend on the number of angles.
Kiitzing separated this genus from Desmidium and Hyalotheca, and as this separation meets with the approbation of the Rev. M. J. Berkeley, I am induced, in deference to their joint opinion rather than from my own conviction of its necessity, to adopt it in the pre- sent work. Mr. H assail is averse to its adoption ; but surely he is mistaken when he puts the differential characters of Didymoprium and Desmidium on the same footing as the presence or absence of a mucous sheath, and thinks that if Didymoprium is a good and valid genus, the absence of a mucous sheath would be sufficient to separate from it Didymoprium Borreri.
The absence or presence of a mucous sheath, or rather its com- parative development, since traces of it may be found in all the fila- mentous Desmidieae, can only be of specific value ; and Mr. Hassall himself, in the analogous example of the Conjugatae, amongst which species of Tyndaridea and Mougeotia have equally developed sheaths, has only in one instance thought it necessary even to allude to its occurrence.
In addition to the characters already enumerated, I may observe that in Desmidium a transverse view shows that the cell itself, irre- spective of the bidentate projections, is angular, and that the endo- chrome is divided into a number of rays corresponding with the number of angles : neither of these circumstances occurs in Didymo- prium.
The filaments in this genus increase in length by the repeated divi- sion of the joints exactly as in the other genera, the new portions being formed between the original segments, which in other respects remain unaltered ; the teeth of the angles furnish a guide to the change
BRITISH DESMIDIE.K. 57
that takes place, for they become more widely separated, and then the new teeth appear, very minute at first, but gradually enlarging, until the new segment equals the older one in breadth.
1. D. Grevillii (Kiitz.) ; sheath distinct ; joints of the filament broader than long, with a thickened border at their junction ; transverse view broadly elHptic.
Desmidium cijUndriciim, Greville, Scot. Crypt. Fl. t. 293. (1827) ; in Hook.
Brit. Fl. V. 2. p. 402. Ag. Consp. Diatom, p. 56. Kutzing, Synop.
Diatom, in Linneea 1833, p. 614. Brebisson, Alg. Fal. p. 64. Harv.
Brit. Alg. p. 197. Menegh. Synop. Desmid. in Linncea 1844, p. 204.
Ralfs, Annals of Nat. Hist. v. 11. p. 373. t. 8. f. 1 ; Trans. ofBot. So- ciety of Edinburgh, \. 2. p. 6. t. 2. Hassall, Brit. Freshwater Algce,
p. 342. t. 83. f. 1. Arthrodesmus? cylindricus, Ehr. Infis. p. 142 (1838). Hyalotheca cylindrica, Ehr. Kurze Nachricht fiber 274 seit dem Abschluss
der Tafeln des grossern Infus. neu beobaehtete Infus. (1840). Desmidium compressum, Corda, Obser. micros, sur les Anim. de Carlsbad,
p. 18 (1840). Didytnoprium Grevillii, Kutzing, Phycologia Generalis, p. 166 (1843) ;
Phy. Germ. p. 141. Didymoprium cylindricum, Ralfs, Annals of Nat. Hist. v. 16. p. 10 (1845) ;
Trans, of Bot. Soc. of Edinburgh, v. 2. p. 164. Hyalotheca Grevillii, Brebisson in lit. (1846).
Appin, Capt. Carmichael. Dolgelley ; Carnarvon ; Penzance, &c., J. R. Cbiltington Common near Pulborougli, and Ashdown Forest, Sussex ; near Southampton, Hants, and Reigate, Surrey, Mr. Je^iner. Cheshunt, Mr. Has- sall. Meath, Mr. Moore. Aberdeenshire, Dr. Dickie and Mr. P. Grant, Manchester, Mr. Williamson. Ambleside, Mr. Sidebotham.
Prussia, Kutzing. Prague ; Carlsbad ; Reichenberg, &c., Corda. Falaise, Brebisson. New York ; Rhodes Island, Bailey.
The filaments in Didymoprium Grevillii are as thick as those of Desmidium Swartzii, which in water is a very similar plant, and are very gelatinous and fragile ; their coloiu- is pale green, but, except when very young, somewhat opake. The joints are connected by a thickened border, and, inclusive of the angles, which are colourless, are rather broader than long, and oval ; the angles are bidentate, their teeth angular. When the angles are not visible the joints are nearly quadrate.
The mucous sheath is very evident, narrower in this plant than in Hyalo- theca dissiliens, and waved at the margin. When the angles are not visible the imdulation of the margin is slight, but becomes more marked as the angles become visible. The sheath is jointed as well as the filament, the lines of separation being sometimes distinctly apparent.
The filaments are regularly twisted, and at about every tenth joint the angles become very perceptible, whilst in the two central joints they are almost invisible ; on slightly altering the position of the filament the angles in the latter become visible, and in the former disappear.
58 BRITISH DESMIDIE-E.
On account of the oval form of the joints their respective angles are sepa- rated, and thus the filament acquires a pinnatifid appearance.
The transverse view is broadly elliptic, with a small process at each end, representing the angles. The mucous sheath is of the same form, and protu- berant over the processes. The endochrome is four- or five-rayed.
I have gathered the conjugated state of Didymoprium Grevillii near Dol- gelley. It has been found in France by M. de Brebisson, but I believe that the present is the first description of it.
Before coupling D. Grevillii separates into single jomts (in only one instance have I observed two joints of one filament still united and conjugated with two other separated joints) ; the cells gape at the margins opposed to each other, exactly as described under Hyalotheca dissiliens, but to a smaller extent, and the original joint is far more easily detected, as one of the teeth of the angle bounds the cleft on each side. As the cleft is narrower, there is an absence of the notch-like appearance so evident on the outer margin of Hyalotheca dissiliens. The cells become connected by a narrow process, often remarkable for its length, and the contents of one cell passes through it into the other, and a sporangium is formed in the same manner as in many ol the Conjugatse. The transfer of the endochrome takes place in a mass, and one part may frequently be observed uniting vdth that in the receiving-cell whilst the other is still in the tube. The joints couple in a crossed position, as in Hyalotheca dissiliens, but the length of the connecting tube permits them to remain apart. The joint which contains the sporangium is but little altered in a transverse view, and when the empty cell becomes detached can scarcely be distinguished, except by contrasting the denseness of the endo- chrome vdth its stellate appearance in the unconnected joints. This detach- ment of the empty cell is a frequent occurrence after the process is completed, nd forms another character of resemblance to those Conjugatse which bear the sporangium vdthin the cell.
In a front view the sporangium is as orbicular as the quadrate form of the joint will permit, being of course rather broader at the side which is cleft, and on that side is usually slightly protuberant. The mucous covering remains unaltered on the joints when they are coupled.
Length of joint ^^ of an inch ; breadth of filament including teeth -^ ; breadth of filament when the teeth are hidden, from -^ to -g-fg- ; breadth of sheath from -^ to ^]-j. Diameter of sporangium 5-^3 .
Tab. II. a. portion of a filament ; b. dividing joint; c. separated joints ; d. transverse view ; e, /, g. conjugated cells ; h, i, k. sporangia.
2. D. Borreri (Ralfs) ; joints inflated, barrel-shaped, longer than broad ; transverse view circular.
Desmidium Borreri, Ralfs, Atmals of Nat. Hist. v. 11. p. 3/5. t. 8. f. 4.
(1843) ; Trans. ofBot. Society 0/ Edinburgh, v. 2. p. 8. t. 2. Hassall,
Brit. Freshioater Algce, p. 343. t. 83. f. 9. Didymoprium Borreri, Ralfs, Annals of Nat. Hist. v. 16. p. 10 (1845) ;
Trans, of Bof. Society of Edinburgh, v. 2. p. Ifi4. Jenner, Flora of
Tunbridge Wells, p. 192.
imiTIRU UESMIDIE.E. 59
Bamhttsina Brehissonii, Kutzing, Phijcologia Germanica, p. 140 (1845). Uyalotheca bamhusina, Bre'bisson in lit. (1816).
CwmBychan,3/;'. Borrer. Dolgelley ; Llanberris ; Tal Sam near Lampeter, J. li. New Forest, Hants ; near Battle ; Ashdown Forest and Cliiltington Common, Sussex, Mr. Jenner. Ireland, Mr. Andrews. Ambleside, West- moreland, Mr. Sidebotham. Manchester, Mr. WiUimnson. Glen Lin, Br. BicJde. Near Aberdeen ; and INIoss Hagg, Banffshire, Mr. P. Grant.
Falaise, Brebisson. Germany, Kutzing. Rhodes Island, Baileij.
Filaments pale green, soon becoming slightly opake, very slender, their mucous sheath wanting or indistinct. In the water this species resembles Hyalotheca dissiliens, but it is less slippery to the touch, and by this cha- racter may often be known when unmixed with other Algse. The filaments are regularly twisted and complete a turn in about 16 joints. The latter are generally nearly twice as long as broad, but in some specimens their length scarcely exceeds their breadth ; they are mflated, so that when the angles are not seen, they resemble small barrels placed end to end, but when the angles are fully displayed their appearance may he compared to the juxtaposition of flower-pots by their mouths, the rims and intervals between which will represent the crenate angles. The angles are bicrenate, and the crenatures being minute and rounded, seem less like an interruption of the outline than in D. Grevillii, but rather as if the angles were attached to the sides of the joints. On account of the length of the joints, the disposition of the endochrome in two portions is very distinct. The joints have not a thickened border at their junction as in D. Grevillii, and the filament separates with less facility into single joints. Occasionally, especially in the short-jointed variety, faint longitudinal lines interrupted at the suture may, on careful examination, be per- ceived, but I find them so uncertain and indistinct, even under the triplet, that I consider it advisable merely to allude to their occurrence ; I have however intro- duced a figure sho^^ing them as Mr. Jenner has observed them in favourable specimens with his powerful achromatic instrument. Mr. Jenner, to whom the credit of their discovery is due, does not find them in every specimen, and regards them as affording an excellent test of the power of the microscope. He informs me that they are situated upon the inner surface of the cell. The transverse view is circular, with two minute opposite projections. The endo- chrome, stellate as in the other species, has five or six rays.
The conjugated state of this species I have gathered sparingly at Dolgelley. We have seen that in this family D. Grevillii is the only known example which has the spore formed within the cell. D. Borreri presents us with another point of analogy between the Desmidiese and the Conjugatse. Most of the former have the frond composed of a single cell, or the filament before conjugating be- comes altogether broken up ; this isbut imperfectly the case here, as the coupling cells have generally other cells remaining, attached either in an unaltered state, or conjugated on their part with portions of other filaments, and thus a kind of network is sometimes formed ; the coupling of the cells crossways occasions a still more confused appearance and renders it exceedingly difficult to trace them. The process is similar to that described under Ihjcdotheca
60 BRITISH DESMIDIE^.
dissiliens, but the segments are still more widely separated on the inner side, and consequently so far thrown back as to cause the attached joints to form a zigzag. The elliptic sporangium lies between the cells, which remain perma- nently attached to it.
KUtzing has established for this plant a distinct genus (Bambusina). The characters which he relies upon are the absence of a mucous sheath, the cask- like joints, and their union, not by a thickened rim as in Bidymopi'ium Gre- villii, but in the manner of the Zygnemata. To these characters, if he had been acquainted with the reproductive state of the two plants, he would doubtless have added the diiferent position of their sporangia.
Even if the presence of a sheath could be supposed to have a generic value, it would not apply to the present question ; for, as Mr. Jenner has pointed out to me, a mucous covering does exist, and may occasionally be detected as a narrow border to the filament. The agreement also between the plants in their angles and the regular twisting of their filaments appear to me to forbid their separation.
Kiitzing suggests* that this plant may be identical with the Gymnozyga moniliformis, Ehr. (Bericht d. Berl. Ac. Novb. 1840). I am luiable to de- termine this point, as I have seen no other notice of Ehrenberg's plant.
This plant was known to M. de Brebisson before it was described in the * Annals of Natural History,' and indeed under the name of Desmidium bam- businum was included by him in a list of Desmidieae inserted in a treatise on the microscope by M. Chevalier in 1839, but I have retained the present name, it being the first under which it was either described or figured.
Length of joint g^ of an inch ; breadth of the joint including teeth ^wzT' Length of sporangium -g-i^, breadth ytos-
Tab. III. a, b. portions of mature filaments ; c. portion of a filament vrith joints dividing ; d, e,f. portions of filaments vrithout endochrome to show the longitudinal markings ; g, h. transverse views ; ^, k. portion of filaments conju- gating ; I, m. sporangia with the empty fronds attached.
3. DESMIDIUM, Ag.
Filament fragile, elongated, triangular or quadrangular, regularly twisted ; joints bidentate at the angles.
The filament is fragile, of a pale green colour and slightly opake. When dried, the British species usually acquire a yellowish appear- ance, and adhere to paper or talc less firmly than plants belonging to allied genera. They are regularly twisted, but being triangular or quadrangular, two of the bidentate angles of each joint are always visible at the margins. The endochrome is divided into linear por- tions by a pale transverse line between the angles.
* Phycologia Germanica, p. 140.
BRITISH DESMIDIEiE. 61
Traces of a mucous sheath have been detected by the Rev. M. J. Berkeley and more recently by myself.
A transverse view shows that the cell is triangular or quadrangular, and that the endochrome has thick rays corresponding in number with the angles; these rays are frequently cloven.
Recent specimens of Desmidium are easily known from other genera by one or two dark waved lines passing down the filament, which appearance is occasioned by the twisting of the angular filament.
1 . D. Swartzii (Ag.) ; filament triangular, equal, with a single longi- tudinal, waved, dark line formed by the third angle ; end view triangular with the endochrome three-rayed.
Biatoma Swartzii, Ag. Bisp. Alg. Svec. (1811). Lyngb. p. 177. t. 61.
Besmidium Swartzii, Ag. Syst. p. 9 (1824). Consp. Crit. Biat. p. 56. Gre- v-ille, Scot. Crijp. Fl. t. 292. Kiitziug, Synopsis Biatom. in Linncea 1833, p. 613 ; Phycologia Germ. p. 141. Greville in Hook. Brit. Fl. V. 2. p. 402. Brebisson, Alg. Fal. p. 53. t. 2. Ehrenberg, Infus, p. 140. t. 10. f. 8. Menegluni, Synop. Besmid. in Linncea 1840, p. 203. Bailey, American Bacillaria in Amer. Journal of Science and Arts, v. 41. p. 288. t. 1. f. 1. Harvey, Manual of Brit. Algce, p. 196. Corda, Observ. Microscop. sur les Animal, de Carlsbad, p. 17. Ralfs, Annals of Nat. Hist. V. 11. p. 375. t. 8. f. 3 ; Trans, of Bot. Soc. of Edin- burgh, V. 2. p. 7. t. 2. Hassall, Brit. Freshwater Algce, p. 344. t. 83. f. 7.
Common. Appin, Capt. Carmichael. Tunbridge Wells, Mr. Bonder. Swansea ; Carnarvon ; Dolgelley ; Penzance, &c., J. R. Many stations in Sussex, and near Southampton, Mr. Jenner. Essex, Mr. Hassall. Caragh Lake, Kerry, Mr. Atidrews. Meath, Mr. Moore. Westmoreland, Mr. Side- botham. Rochdale, Mr. Coates. Manchester, Mr. Williamson. Aberdeen- shire, Br. BicJcie and Mr. P. Grant.
Sweden, Agardh. North Germany, Martens, Kiitzing and Ehrenberg. Carlsbad ; Prague ; Reichenberg, Corda. Throughout the United States, Bailey. Falaise, Brebisson.
The filaments are elongated and very fragile, but separate spontaneously mto single joints less readily than in Hyalotheca dissiliens and Bidymoprium Grevillii. They adhere but slightly to paper. They are triangular, and, when viewed under the lens, the margins are always formed by two of the three angles in turn, whilst the dark line regularly passing from side to side marks the third angle and shows that the filament has a spiral twisting in about 16 joints. On examining the filament where the dark Une touches the margin, if we first raise and then depress the lens, both angles at the point of apparent contact may be distinctly seen.
The joints are in the front view somewhat quadrangular, broader than long, and each angle has two minute, slightly angidar teeth. The notch between the teeth is veiy distinct but not gaping. The joints are connected by a
62 BRITISH DESMIDIE^.
thickened margin, which partly fills the notch formed between the joints by the projection of the angles, whence the filament has a piunatifid appearance.
The transverse view is triangular ; the angles are blunt and the sides slightly concave. The endochrome is in three portions, placed in the angles and connected together at the centre ; but this arrangement of the endo- chrome is seen only when the joints separate spontaneously. The rays are usually bipartite. When a joint is separated by force under the microscope, a cloud of minute granules is poured out and for an mstant obscures the view.
Mr. Borrer has kindly presented me with a portion of a specimen of the plant here described, which was given him by Mr. Dawson Turner as the Conferva dissiliens of Dillwyn.
I have gathered at Dolgelley some fragments of this plant which had the endochrome condensed into a sporangium-like body in the centre of each joint. As in every other species of this family m which the reproductive body has been detected, it is the result of the coupling of the cells, I think it best merely to direct attention to the fact I have mentioned, leaving its nature to be determined by future observation.
Length of joint from -2^00^ to y^Vb^ ^^ ^'^ ^^^^^ 5 breadth of filament ^3.
Tab. IV. a. portion of a mature filament ; b. portion of a filament with the joints dividing ; c, d, e, transverse views ; f. sporangia ?
2. D. quadrangulatum (Ralfs) ; filaments quadrangular, varying in breadth from the twisting of the filament and having two longi- tudinal waved lines; the end view quadrangular with the endo- chrome four- rayed.
Desmidium quadrangulatum, Ralfs, in Annals of Nat. Hist. v. 15. p. 405.
t. 12. f. 9. (1845) ; Trans, of Bat. Soc. of Edinburgh, v. 2. p. 163. Desmidium quadrangulare, Kutz. Phy. Germ. p. 141 (1845).
Hab. In a boggy pool at Bologas near Penzance ; Dolgelley, /. R. Amble- side, Mr. Sidebotham. Aberdeen, Br. Dickie and Mr. P. Grant.
The Harz, Germany, Kilt zing.
Mr. Berkeley and Mr. Borrer regard this plant as a variety of D. Swartzii, and certainly all the more obvious distmctive marks depend upon the filament being quadrangular in one case and triangular in the other*. As I have gathered it for two succeeding years quite unmixed with Desmidium Swartzii, and as Mr. Berkeley well observes (in a letter), that " whether considered as a species or variety, it is a remarkable plant and well-deserving of notice," I have preferred to describe it as distinct, although I do not consider the point free from doubt. As there are three sides in one plant and four in the other, whilst the sides in both are equal, the filament of D. quadrangulatum is stouter ; for the same reason, instead of one dark longitudinal line it has two
* " Est-il reellement plus distinct du D. Swartzii que les Staurastr. a quatre ravons dcs Staur. a (rois ravons?" — Brvbisson in lit.
BRITISH DESMIDIE.'E. 63
lines running from side to side and crossing each other : the additional line of course depends on the additional angle. When these lines approach the opposite margins of the filament only one side is presented to the eye, and the filament is then of the same breadth as in D. Sicartzii, but as it is regu- larly twisted its apparent breadth varies, being greatest where both dark lines cross each other in the middle. The end view also has one angle more, and therefore the endochrome exhibits four instead of three rays. I may however observe, that the teeth, as JNIr. Jenner has pointed out, are rounded ill my specimens of D. qvadraiiyuhitum and angular in B. Sicartzii ; but further experience must determine whether this character is constant.
D. quadrangulatum requires about 40 jomts to complete a turn, or before the same angle again appears at the same margin.
It affords some sanction to this arrangement, that shortly after my notice of this plant appeared hi the ' Annals of Natural History,' it was described by Kiitzing in his ' Phycologia Germanica' as a distmct species.
Length of joint y^JT of ai inch; least breadth or side in transverse view ■B^oT '■> greatest breadth, or diagonal, in transverse view -^-^.
Tab. V. a. portion of a filament ; h. filament less magnified ; c. empty joint ; d, e. transverse ^-iews.
4. APTOGONUM.
Filament elongated, triangular or plane ; joints bicrenate at the mar- gins : an oval foramen between the joints.
The filaments are elongated, jointed, fragile, and either triangular or plane; the joints at the angles are bicrenate, and at their junction are excavated at the centre, and thus form a series of oval foramina. The endochrome is bipartite.
By Brebisson, Meneghini and Kiitzing this plant is included in Desmidium, and certainly the state with triangular filaments does at first sight appear closely allied to Desmidium Swartzii ; but the large oval foramen between the joints is so remarkable a character, that I must concur with Ehrenberg in placing it in a separate genus. As however Ehrenberg's name, Odontella, had previously been given by Agardh to some Diatomaceae, it became necessary to find another name.
Ehrenberg included Sphaerozosma in his Odontella, but the present genus is essentially distinct from Spharozosma ; in the latter the joints have their margins incised or sinuated, and gland-like processes at their junctions, and it is merely by the interposition of these processes that the joints are now and then slightly separated. In this genus,
64 BRITISH DESMIDIE^E.
on the contrary, the joints have two prominent teeth at the margins or angles, and the foramen results from the excavation or concavity of the joint itself, and not from the presence of glands.
1. A. Desmidium (Ehr.) ; joints in the front view quadrangular,
broader than long ; crenatures distinct.
a. Filaments triangular, regularly twisted ; crenatures rounded.
Desmidium aptoffonum, Breb. Alff. Fal. p. 65. t. 2. (1835). Menegh. Syn. Desm. in Linn. 1840, p. 203. Kutz. Phy. Germ. p. 141.
/3. Filaments plane ; crenatures shallower and slightly angular. Odontella Desmidium, Ehr. In/us. p. 153. t. 16. f. 4. (1838).
a. Ambleside, Westmoreland, Mr. Sidebotham. Dolgelley, J. R.
jo. Ambleside, Mr. Sidebotham.
North Germany, Ehrenberg. Carlsbad, Corda. Falaise, Brebisson.
The filaments, which are slenderer than those of Desmidium Swartzii, are slightly mucous, but have no distinct sheath. The joints are nearly as long as broad, and being excavated at their junction and connected only at the margins, they leave oval foramina between them.
The two states of this plant are so different that they seem at first sight distinct species. In a. the filaments are triangular, and being regularly twisted as in Desmidium, they in like manner exhibit a dark waved longitudinal lirte, marking the third angle ; hence the foramina are far less conspicuous in this than in the plane variety, as they are obscured by the junctions of the third angle. When the dark line which denotes that angle approaches the margin of the filament they are more evident, and their size and figure may be ascer- tained. The marginal crenatures are deeper and more rounded, which fact, as Mr. Jenner has justly remarked to me, makes it doubtful whether a similar character can be relied on for distinguishing Desmidium quadranyulatum from Desmidium Swartzii. The end view is triangular ; the sides are slightly concave and the angles rounded and somewhat thickened. The en- dochrome in this aspect has the rays equal in number to the angles, each ray being usually bipartite.
The variety /3. is an elegant microscopic object. Its foramina are large and conspicuous. The only specimens I have seen were gathered by Mr. Side- botham. Its characters are so distmct that it is unnecessary to compare this variety with any other plant.
A careless observer might mistake the triangular form for Desmidium Swartzii. It differs however not only in the presence of foramina, but its filaments are more slender and its joints longer in comparison with their breadth.
Several filamentous Desmidiese have no slight resemblance to Taeniae, and none more than this species.
Length of joint of a. (Dolgelley specimen), including connecting processes, Y^Jg 5- of an inch ; length between foramina vgVs 5 breadth of joint ygVo-
BRITISH DESMIDIEiE. 65
/3. (Ambleside specimen.) Length of joint, iwluding the connecting i)ro- cesses, -^ ^\ ^ ; length between foramina y^Vr 5 breadth of joint -^^.
Tab. XXXII. f. 1 . c. portion of mature filament ; b, c, d. transverse views ; e. portion of a filament of /3. (Ambleside specimen) ; /. portion of a filament with dividing joints ; ff. two joints in an oblique position ; h. lateral view.
5. SPH.EROZOSMA, Corda.
Filament plane, fragile ; joints closely united by means of glandular processes, and deeply divided on each side, thus forming two seg- ments, and giving a pinnatifid appearance to the filament.
The filaments are pale green, gelatinous, simple, plane, have a pin- natifid appearance from the division of the joints into two segments, are fragile, and finally separate into single joints. I have not observed that the filaments are twisted, as in Desmidium and Didy- moprium. At the junction of the joints there are on each margin one or two minute glands or processes which are scarcely discernible in the front view, and do not interfere with the close junction of the joints. The transverse view is linear or oblong, and the processes, one or two at each side, are much more evident than in the front view.
This genus differs from Desmidium, Didymoprium and Hyalotheca in its flat filaments (which are not twisted), in the deep division of the joints into segments, and especially in the presence of the minute gland-like processes at the junction of the joints.
On account of its deeply constricted joints, this genus forms a con- necting link between the preceding and following genera.
In Sphcerozosma, as in the other genera with deeply constricted cells, the segments are frequently unequal during the growth of the plant, and they become in like manner equal when it approaches maturity, and its joints no longer divide.
1. S. vertebratum (Breb.) ; joints as broad as long, deeply divided into two segments by a narrow notch on each side. Junction-glands oblique, solitary at the centre of each margin.
Desmidium vertebratum, Breb. Alg. Fal. p. 65. t. 2. (1835).
Sph(srozosma elegans, Corda, Ahnanach de Carlsbad, 1835, t. 4. fig. 37?;
Observ. Micros, snr les Animal, de Carlsbad, p. 21. t. 4. f. 30? Hass.
Br.Alff.p. 348. t. 84. f . 1. Odontellal unidentata, Ehr. Infus. p. 159 (1838). Isthmia vertebrata, Menegh. Synop. Desmicl. in Linncea 1840, p. 205. Desmidium compressum, Ralfs, in Annals of Nat. Hist. v. 9. p. 253 (1842).
GG BRITISH DESMIDIE.E.
Sehistochilum unidejitutum, Ralfs, in Jenrn^ra Fl. of TunhriJge Wells, p. 192
(1845). Sphterozostna unidentatvm, Ralfs, in Annals of Nat. Hist. v. 16. p. 14. t. 3.
f. 7. (1845) ; Trans, of Bot. Society of Edinburgh, v. 2. p. 167. Isthnosira vertebrata, Kiitz. Phycologia Germanica, p. 141 (1845).
Hab. Chy-au-hal and Kerris Moor near Penzance ; Dolgelley, /. R. Ro- therfield and near Tunbridge Wells, Mr. Jenner. Isle of Sheppey, Mr. Bowerbank. Ambleside, Mr. Sidebotham.
France, De Brebisson. Carlsbad, Corda. North Germany, Eh'enberg and Kiitzing. West Point, New York, Bailey.
The filaments are much compressed, and the joints, which are nearly equal in length and breadth, are so deeply constricted that at first sight a single one might be mistaken for two. This is more especially the case whilst the endochrome obscures the view of the union of the segments ; as soon however as the joint becomes empty, its nature is distinctly seen. Though in other respects symmetrical, one segment is frequently much smaller than the other.
At the centre, where the joints are connected, is a minute gland or process arising from each margin. The projection of these glands is easily seen, even before the joints separate.
By a transverse \'iew the joints are shown to be compressed, and the oblique glands, which are globular and supported on a very short stipes, are very distinct. In this view the joints are about twice as long as broad, with slightly concave sides, and the endochrome is stellate with from four to six rays.
In a recent state Sphcerozosma vertebratum is very gelatinous and furnished with a broad mucous sheath, which from its tenuity and want of colour is very difficult of detection, and consequently I at first described it as absent. When the plant occurs unmixed with others, the presence of the sheath is indicated by the distinct and parallel filaments exactly as in Hyalotheca mucosa ; for in both plants this appearance is produced by its great breadth, which prevents the closer contact of the coloured centres. The sheath is sufficiently apparent in specimens preserved on glass, and is on each side nearly as broad as the filament. In dried specimens it has an irregular waved margin and faint transverse markings.
The greater difficulty of detecting the sheath in recent specimens of Hya- lotheca mucosa and S. vertebratum than in Hyalotheca dissiliens and Didy- moprium Grevillii, seems to depend more upon its condition in the two former than upon its greater breadth. As in them it is less condensed, it is not only liable to be confounded with the water in which it is viewed, but is also more soluble in it. When Didymoprium Grevillii is mounted in fluid, the sheath remains as distinct as in recent specimens ; the case is nearly the same when Hyalotheca dissiliens is so treated, but not so in respect of the present plant, the sheath of which seems to be dissolved.
Length of joint xtt? ^^ ^^ ^^^ ' breadth of segments from ^^ to -^ ; breadth at constriction -^rrr 5 diameter of sporangium y^Vo •
Tab. YI. f. \. a, b. portions of filaments; c. empty joints; d. side view; e. glands in front ^iew ; /, g. transverse views. Tab. XXXII. f. 2. a, b, c. sporangia.
BRITISH DESMIDIE^:. 67
2. S. excavatmn (Ralfs) ; joints longer than broad, having a deep sinus ou both sides, and two sessile glands on each margin at their junction.
Schistochihnn exeavatum, Ralfs, m Jenner's Fl. of Tunbridge Wells, p. 192
(18-15). Spharozosma excavata, Ralfs, in Annals of Nat. Hist. v. 16. p. 15. t. 3. f. 8.
(1845); Trans, of Bot. Society of Edinburgh, v. 2. p. 168. Hass.
Brit. Freshwater Jig. p. 349.
Hab. Pools. Dolgelley and Penzance, J. i2. Cross-in-hand, and Ashdown Forest, Sussex ; bogs at Fisher's Castle, Kent ; Farnham, Surrey, and near Southampton, Mr. Jenner. Bristol, Mr. Broome. iVmbleside, Mr. Side- botham. Rochdale, 3Ir. Coates.
Falaise, Brebisson. West Point, New York, Baileij.
\eTy minute, seldom more than twenty-five joints in the filament, which is fragile and finally separates into single joints ; at their junction, in the front view, are two minute glands or processes, situated one near each angle, and nearly im"isible before the escape of the endochrome. The joints are nearly twice as long as broad and much constricted in the middle ; the constriction is hke an excavation or broad sinus on each side, so that the margins of tlie filament appear sinuated. The endochrome is pale bluish green with minute scattered granules.
The transverse view is oblong with four sessile glands, two on each side, and situated near the ends.
From their pale colour and minute size I have experienced much difficulty in determining the form of the angles, which in some specimens seem to me entire, but in others emarginate. Mr. Jenner, using a more powerful mi- croscope, informs me that each is apparently furnished with three minute teeth, which can be detected only when favourably situated for observation. On each segment of the empty joint he finds three transAcrse series of minute granules, whose appearance at the margins produces this mmutely toothed appearance.
I have frequently gathered this species, but always in small quantity, mixed with other Desmidiese ; I am therefore miable to decide whether it possesses a mucous sheath.
The sporangia of S. exeavatum have been gathered near Farnham in Surrey, and at Cross-in-hand, Sussex, by Mr. Jenner, who sent his specimen to me for examination. The joints after separation couple ; the sporangium is situated between them, and is large compared with the conjugating cells. It is elliptical, and the empty cells are closely connected with it, one at each end. As the specimen was mounted, I was prevented from using the triplet ; but from Mr. Jenner' s description, the conjugation takes place from their flat or front surfaces, and not in the usual manner from one of the lateral sinuses ; therefore either one of the ends or one of the lateral margins will be presented to the eye.
Length of joints ^5^ 5 of an inch ; breadth of segments 3^'-^ ; breadth at constriction ^Vo ^ length of sporangium y^ ; breadth from -^^ to ^pgL^.
F
68 BRITISH DESMIDIE/E.
Tab. VI. fig. 2. a. portion of a filament ; Ij. portion of a filament with empty joints ; c. empty joint to show the granules ; d. transverse view ; e, f, g. sporangia.
** Frond simple {binate only when dividing), consisting of two seg- ments united by a suture, where it is most frequently constricted.
6. MICRASTERIAS, Ag.
Frond simple, lenticular, deeply divided into two, lobed segments ; the lobes inciso-dentate (rarely only bidentate), and generally radiant.
The fronds are simple, nearly flat, without inflated protuberances, and divided nearly to the centre, so that the segments are semi-orbi- cular, and usually in close contact with each other along their entire breadth; each is deeply divided into lobes, which are generally arranged in a radiant manner and regularly cleft and dentate at the margin.
In two species sporangia have been detected ; they are large, glo- bular, and furnished with stout spines, which at first are simple, but finally become branched at the apex. In the perfect state they are particularly interesting from their resemblance to the fossil " Xan- thidia" of Ehrenberg and others.
The orbicular, plane and deeply incised fronds will distinguish Micrasterias from all other genera in this family. In Euastrum, the only one wdth which it can be confounded, the fronds are oblong and the lobes are not incised.
As the plants to which Agardh affixed the name of Micrasterias are probably all included under the above description, I have followed Meneghini in retaining that name for this genus, especially as it seems to me that not one of Agardh's species is contained in the Micrasterias of Ehrenberg, who in fact intended by it a very different genus, the Pediastrum of Meyen*.
Although Micrasterias contains but few species, they admit of an arrangement in three sections.
The species in the first section present some of the most beautiful microscopic objects amongst the Desmidieae. They are distinctly
* " Nomen a el. Agardh propositum et perperam ab aliis Pediastris affixum, et cum novo illo Euastrum commutatum servandum." — Menegh. Syn. Besmid. in Lirmcea 1840, p. 215.
BRITISH DESMIDIE.li. 69
visible, appearing to the naked eye like minute green dots. The microscope shows them to be circular and their segments deeply di- vided into five lobes. The end lobe, which is narrowest, is simple, emarginate, and its corners dentate ; the lateral lobes are several times dichotomously incised, the ultimate subdivisions emarginate or biden- tate ; frequently the middle lobes are once more dichotomous than the basal lobes, so as to have twice the number of incisions. The lobes and their subdivisions are alike cuneate, approximate and radiant.
In the second section the fronds are smaller, and elliptic rather than circular ; the end lobe is somewhat exserted and diverges from the lateral lobes. The division on each side into basal and middle lobes is less marked, so that in some species the segments may more appropriately be called three- than five-lobed. As in the first section the lobes are cuneate and radiant, they are also dichotomously incised, and their ultimate subdivisions are dentate, but fewer in number than in the former, in which there are four to eight in each lateral lobe, M'hilst in this section the ultimate subdivisions in the basal and middle lobes are rarely more than two.
The third section agrees with the first, inasmuch as its species are also circular, though considerably smaller ; its essential diflference de- pends on the great breadth of the end lobes and the very slight in- , cisions between the lateral ones.
In the fourth section there is but a single species. It is oblong, its segments are five-lobed, and their lobes slightly emarginate.
The form of the frond of the species belonging to the fifth section differs from that of the preceding ones. It is not only smaller, but each segment is again constricted, and the direction of the lobes is horizontal. Unlike the lobes in the foregoing sections, these are broadest at the base and attenuated upwards, and are of course di- vergent ; their extremities are simply bidentate. The margin of the end is convex or straight, not emarginate.
For the reception of one species belonging to this section, Mr. Hassall has constituted his new genus Holocystis ; but, allowing that the plants I have placed here differ in form from the other species in the genus, and giving no opinion on the propriety of their removal, I think it better at present to retain them in Micrasterias, because some of the forms have been regarded by Ehrenberg and Meneghini as merely young states of other species j and Kiitzing, who has described
F 2
*J0 BRITISH DESMIDIKiE.
them as distinct, has not separated them from the other species of Micrasterias.
* Frond circular ; segments five-lobed ; lobes approximate, the end
lobe narrow.
1. M. denticulata (Br^b.) ; frond orbicular, smooth; segments five- lobed ; lobes dichotomously divided, the ultimate subdivisions truncato-emarginate with rounded angles.
Micrasterias denticulata, Brebisson, Alg, Fat. p. 54. t. 8. (1835). Euastrum Rota, Elirenberg, Infus. t. 12. f. 1. «. (1838). Bailey, Amer. Bacil.
in Amer. Journal of Science and Arts, v. 41. t. 1. f. 22. Micrasterias Rota, Meneghini, Syn. Desmid. in Linncea 1840, p. 215. Micrasterias rot at a, Ralfs, Annals of Nat. Hist. v. 14. t. 6. f. 1. (1844) ;
Trans, of Bot. Society of Edinburgh, v. 2. t. 10.
Common. Wales ; Penzance, &c.,J.R. Barmouth, Rev. T. Sahoey. Near Soi;thampton ; Sussex and Kent, Mr. Jenner. Henfield, Mr. Borrer. Ste- venston, Ayrshire, Rev. D. Bandshorough. Yate near Bristol, Mr. Broome. Ambleside, Westmoreland, Mr. Sidebotham. Aberdeenshire, Dr. Dickie and Mr. P. Grant.
Falaise, Brebisson. Germany, Ehrenberg . West Point, New York, Bailey.
The frond is large and circular ; each segment is five-lobed. The end lobe is the narrowest, is simply emarginate, and often appears more turgid than the others. The lateral lobes are dichotomously incised, their ultimate sub- divisions truncato-emarginate. The lobes and subdivisions are alike cuneate, approximate, and radiating from the centre. The endochrome is bright green, and the starch vesicles scattered and conspicuous. Frequently the margin of the frond is colourless.
I once gathered sporangia of this species rather plentifully in a boggy pool near Dolgelley. Tbe lenticular shape of the fronds and their conjugation in a crossed position render it almost impossible to obtain a satisfactory view without displacing them. The process appears similar to what takes place in Staurastrum dejectmn ; the contents of both fronds unite and form a globular sporangium between them, the connexion between this sporangium and the empty segments being ascertained merely by their contiguity and by their relative position, which undergoes no change during the movements of the sporangium. The sporangium is inclosed in a fine membrane, and its surface is gradually furnished with scattered, stout, elongated spines, which are at first simple and their apex obtuse, but this afterwards becomes forked or trifid, and its divisions finally are again branched and frequently more or less re- curved. The sporangia are of considerable size, — a necessary consequence of the union of the contents of both fronds.
The truncate ends of the subdivisions distinguish this species from Micra- sterias rotata, to which it is very closely allied.
Length of frond yy^ of an inch ; breadth of segment ~-^ ; breadth at con-
BRITISH DESMIDIEiE. 71
striction -^ ; diameter of sporangium from ^ J-y to -^ ; length of spine from
TTTg' ''" 7 4 1-
Tab. VII. fig. 1. a. mature frond ; b. dividing frond j c, d, e and/, different stages of sporangia ; </. sporangium magnified 400 times.
2. M. rotata (Grev.) ; frond orbicular, smooth ; segments five-lobed ; lobes dichotomously incised, ultimate subdivisions bidentate.
EchineUa rotata, Greville, in Hookers Brit. Fl. v. 2. p. 398 (1830). Euastrum Rota, Ehr. Abh. derBerJ. Ak. (1831), p. 82 ; Infus. t. 12. f. \.c,e.
Kiitzing, Phijcoloyia Germanica, p. 134. Eutomia rotata, Harvey, Manual of Brit. Algae, p. 187 (1841). Micrasterias rotata, Ralfs, Annals of Nat. Hist. v. 14. p. 259. t. 6. f. 1
(1844) ; Trans, of Bat. Soc. of Edinburgh, v. 2. p. 131. t. 10.
Common. Appin, Capt. Carmicliael. North and South Wales ; Dartmoor and Penzance, J. R. Sussex, Surrey and Kent, 3Ir. Jenner. Near Bristol, Mr. Broome. Aberdeen, Dr. Dickie. Ambleside, Mr. Sidebotham.
Germany, Ehrenberg . Falaise, Brebisson. Rhode Island, Bailey.
M. rotata is very similar to M. denticulata, but differs from it in having the ultimate subdivisions dentated. The end lobe is usually slightly exserted, and the middle lobes have eight subdivisions instead of four ; I have never- theless some doubt whether this plant is not a variety of 31. denticulata, as the angles are sometimes merely acute instead of being prolonged into teeth.
Length of frond -^ of an inch ; breadth yij.
Tab. VIII. fig. 1. a. frond v^^ith endochrome ; b. empty frond.
3. M. fimbriata, ; frond orbicular, smooth ; segments five-lobed ;
lobes dichotomously incised ; ultimate subdivisions obtusely emar- ginate, spinoso-mucronate.
Micrasterias Rota, in part, Ehr. Infus. t. 12. f. d. (1838). In a boggy pool near Dolgelley, /. R. Germany, Ehrenberg.
The frond is large and circular ; the segments five-lobed ; the end lobe linear-cuneate, having a broad shallow notch and two or three spines or mucros at each angle, the angles rounded. As in the preceding species, the lateral lobes are dichotomously incised, but their incisions are more shallow, the ultimate subdivisions rounded and slightly emarginate, and each furnished with two spines, w-hich are often curved.
The basal lobes are twice and the middle lobes usually three times dichoto- mous, consequently the latter may have eight subdivisions whilst the former have only four. The end lobe is somewhat exserted, and frequently also there is an elongation of the subdivisions of the basal lobes which border the central constriction.
Length of frond y^-g of an inch ; breadth ■^\^.
Tab. VIII. fig. 2. a. empty frond ; b. frond with endochrome.
72 BRITISH DESMIDIEjE.
4. M. radiosa (Ag.) ; frond orbicular, smooth ; segments five-lobed ; lobes dichotomously divided ; ultimate subdivisions inflated, atte- nuated at the end.
Micrasteinas radiosa, Ag. Bot. Zeit. 1827.
Euastrum Sol, Ehr. Verhreitung und Einfluss des mikroskopischen Lebens in Slid- und Nord-A7nerika, 1843, t. 4. f. 16.
In a small pool a little below the outlet of Llyn Gweruan near Dolgelley, J. R.
Maine to Virginia, Bailey.
The frond, which is about the size of that of M. rotata, is orbicular ; seg- ments five-lobed. The end lobe is narrow-cuneate, emarginate, and its angles dentate. The lateral lobes are dichotomously divided as in all the preceding species, but the subdivisions, especially the ultimate ones, are somewhat inflated, and their extremities are either bidentate or taper into a short mucro.
Micrasterias radiosa approaches M. rotata more nearly than any other species, but it differs from all in its inflated subdivisions. The extremities of the subdivisions in all the preceding species are truncate, but in this they usually taper into a point.
Length of frond y^-g of an inch ; breadth ^-i-g .
Tab. VIII. fig. 3. a. frond with endochrome ; b. empty frond.
5. M. papillifera (Breb.) ; frond orbicular, with marginal gland-like teeth ; segments five-lobed ; lobes dichotomously incised ; the prin- cipal sinuses bordered by a rov^!^ of minute granules.
Mici'asterias 2iapillifera, Brebisson in lit. cum icone (1846).
Hab. Dolgelley and Penzance, J. R. Sussex, Hants and Surrey, Mr. Jenner. Ambleside, Mr. Sidebotham. Aberdeen, Dr. Dickie and Mr. P. Grant.
Falaise, Brebisson. West Point, New York, Bailey.
The frond is smaller than in M. rotata ; the segments five-lobed ; the end lobe is nearly as broad as the others and emarginate, its angles are dentate. The lateral lobes are usually equal and dichotomously divided, the incisions rather shallow, and the ultimate subdivisions terminated by two or three gland- like teeth.
The surface of the frond has a row of minute hyaline granules or spines bordering the prmcipal sinvises, but in other respects it is smooth. Except in the empty frond, these granules, though sometimes evident, are frequently de- tected with difficulty ; in order to perceive them, the lens should be gradually withdrawn u.ntil the endochrome becomes less distinct, when they will appear like puncta.
The endochrome is brownish green, and the starch vesicles minute and numerous.
The sporangia, which I have gathered at Dolgelley, are similar to those of M. denticiilnta, but smaller.
M. papiUifera is a very distinct species, and its characters were detected
BRITISH I>ESMID1E.K. 'JS
about the same time by Mr. Jenner and myself. It may be distinguished at first sight from all the preceding species by its smaller size, the gland-like ap- pearance of the marginal teeth, the browner colour of the endochrome, and the smaller and more crowded starch vesicles. It is more difficult to perceive the puncta-like granules which border the sinuses.
This plant agrees more nearly with M. apiculata, a species not yet detected in Britain ; but in M. apiculata the endochrome is of a brighter green, and the spines, which are scattered over the surface, are far more conspicuous.
Length of frond from -^ to -^ of an inch ; breadth from ^ to ^ ; diameter of sporangium -g-|^ ; length of spine y5^2-
Tab. IX. fig. 1 . a. frond with endochrome ; b, c. empty fronds ; d and e. end and lateral views from drawings by M. De Brebisson ; /. sporangium ; ff. sporangium magnified 400 times.
** Frond subelliptic ; segments three- or five-lobed ; lobes radiant, the end one somewhat exserted and divergent.
6. M. f areata (Ag.) ; segments five-lobed ; lobes bifid, their divisions linear, divergent, and forked at the apex.
Micrasterias furcata, Ag. Bot. Zeit. (1827). Kiitz. Synop. Biatom. in Lin- ncea 1833, p. G03. Menegh. Si/nop. Desmid. in Linncea 1840, p. 216.
Micrasterias Meliteyisis, Ralfs, in Annals of Nat. Hist. v. 14. p. 260. t. 6. f. 2. (bad) (1844) ; Trans, of Bot. Soc. of Edinburgh, p. 132.
Mici'asterias radiata, Hass. Brit. Freshwater Alg. p. 386 (1845).
Hab. In a small pool a little below the outlet of Llyn Gwernan near Dol- gelley, also in the stream that issues from the lake : very rare, /. R.
Worden's Pond, Rhode Island, Bailey.
The frond is smaller than that of M. rotata ; its outline is broadly elliptic, sometimes almost circular. Each segment is deeply five-lobed ; all the lobes are bifid and their subdivisions linear and forked at the extremity, the forks being usually incurved. The end lobe is broadest and somewhat exserted ; its divisions are more divergent and the sinus more rounded than in the lateral lobes. The endochrome is green with scattered starch vesicles, and seldom extends beyond the bifurcation of the lobes.
M. furcata bears some resemblance to M. Crux-Melitensis, but is far more elegant, its incisions are deeper, its divisions more slender, and the terminal notch is incurved in a forceps-like manner.
Length of frond yir of an inch ; breadth -^^.
Tab. IX. fig. 2. a. frond with endochrome ; b. empty frond.
7. M. Crux-Melitensis (Ehr.) ; frond rotundato-elliptic ; segments sub-five-lobed ; lobes bifid, subdivisions short, stout and bidentate at the apex.
Euastrum Crux-Melitensis, YAw. Abh. d. Berl. Ah. p. 82 (1831); Infus. p. 162. t. 12. f. 3. Pritch. Infus. p. 196. f. 124. Bailey, Amer. Bacil. t. I. f. 23.
74 BRITISH DESMIDIE^.
Mierasterias melitensis, Menegh. Synop. Desmid. in Linncea 1840, p. 216.
Ilab. Pools, very rare. Dolgelley, J. R. Congleton, Cheshire, and Arable- side, Westmoreland, Mr. Sidebofham, Henfield, Mr, Jenner.
Germany, Ehrenherg. Falaise, Brebisson. Maine to Virginia, Bailey.
The frond is about the size of that of M. fur cat a and similarly divided, but the incisions are less deep, the subdivisions stouter and less divergent, and their extremities are bidentate rather than forked ; the end lobe also is more suddenly contracted beneath the bifurcation. The colouring matter extends nearly to the margin.
Mr. Jenner finds the empty fronds very delicately punctated.
Length of frond ^h^ of an inch ; breadth g-lr-
Tab. IX. fig. 3. a. frond with endochrome ; b. empty frond.
8. M. morsa ; frond angular-elliptic ; segments three-lobed, end
lobe with bipartite angles ; lateral lobes broad, margin concave in- ciso-serrate.
Euastrum (No. 4), Bailey, Amer. Bacil. t. 1. f. 25.
a. Serratures distinct.
y8. Serratures obscure.
Hab. a. In a bog near Llyn Gwernan, Dolgelley, /. R.
j3. Pools near the Quaker's Chapel, Dolgelley, /. R. Ashdown Forest, Mr. Jenner,
New York to Virginia, Bailey,
The frond of Mierasterias morsa is as large as that of M. Crux-Melitensis. The segments are three-lobed ; the end lobe is broad, cuneate and somewhat exserted, has a broad shallow notch, and at each angle is bifid ; the divisions are narrow, and each terminated by two or three minute teeth. The lateral lobes are broad and cimeate, and their margm is concave, symmetrically incised and serrated.
In /3. the characters are less strongly marked, the lateral lobes are waved rather than toothed, and also more irregular.
Mierasterias morsa diifers from M. Crux-Melitensis in the bifid angles of the end lobes and in the concave and serrated margin, as well as the less-di- vided state of the lateral lobes. The concave margin of the lateral lobes pro- duces a more angular appearance of the frond than in the other species, and the plant, especially in the variety /3, acquires some similarity of outline to Euastrum verrucosum, but its serrated margin and the bifid angles of its end lobes oblige me to place it in Mierasterias.
Length of frond ^-L. of an inch ; breadth -g-j-j.
Tab. X. fig. 1 . a. frond with endochrome ; b, c. empty fronds ; d, e. fronds of R.
BRITISH DESMIDIE^. 7^
*** Fronds orbicular ; segments obscurely five-lobed, the end one
broadest.
1). M. truncata (Corda) ; frond orbicular ; segments with five shal- low lobes, the end one very broad, truncated, lateral ones inciso- dentate.
CosmariuM tnincatum, Corda, Aim. de Carhb. 1835, p. 121. f. 23. Euastrum Rota, Ehr. Infus. t. 12. f. \. g, h. (1838). Micrasterias Rota (yoimg), Menegh. Synop. Besmid. p. 215 (1840). Euastrum semiradiatum, Breb. in Menegh, Sj/noj}. Desmid. (1840). Kiitzing,
Phycoloyia Germ. p. 134. Euastrum (No. 4), Bailey, Amer. Bacil. f. 24. (1841). Micrasterias rotata, Ralfs, Atinals of Nat. Hist. v. 14. t. 6. f. 1. b. (inferior)
(1844) ; Trans, of Bot. Soc. of Edin. v. 2. t. 10. Micrasterias truncata, Breb. in lit. (1846).
Common. Sussex and Hampshire, Mr. Jenner. Dolgelley, Penzance, &c., /. R. Aberdeen, Dr. Dickie and Mr. P. Grant. Near Bristol, Mr. Broome. Ambleside, "Westmoreland, Mr. Sidebotham. Kerry, Mr. Andrews.
Germany, Corda, Kutzing. Falaise, Brebisson. United States, Bailey.
The frond is minute and circular, the segments are five-lobed, and the sepa- rating smuses shallow, especially those between the lateral and intermediate lobes. The comers of the terminal lobe, which is broadly cuneate and truncate, are bidentate, and the lateral lobes are inciso-dentate.
Mr. Jenner and myself have hitherto differed respecting this plant. He has considered it distmct, whilst I have been disposed to regard it as the young state of M. rotata, and it was figured as such in the plate (already engraved) of that species ; but I have learnt since from M. de BrcTjisson and Professor Kutzing, that they entertained no doubt of the distinctness of this species and had so described it, and I have myself met with specimens con- taining in abundance starch vesicles ; I therefore hasten to admit its claims to the rank of a distinct species.
Length of frond -^\-^ of an inch ; breadth -^.
Tab. VIII. fig. 4. and Tab. X. fig. 5. a. frond with endochrome ; b. empty frond ; c. end view ; d. side view.
10. M.crenata (Breb.); frond orbicular; segments with five shallow lobes, the end one very broad and convex at the margin, lateral ones nearly entire.
Micrasterias rotata, Ralfs, A7in. of Nat. Hist. v. 14. t. 6. f. 1. b. (superior)
(1844) ; Trans, of Bot. Soc. of Edin. v. 2. t. 10. Micrasterias crenata, Breb. in lit. (1846).
Dolgelley, J. R. Sussex, Mr. Jenner.
The frond is minute, of the same size as that of 31. truncata, and cir- cular. The segments are five-lobed, the terminal one broad, cmieate, entire and rounded at the margin. The lateral lobes are sometimes entire, but more usually crenate, occasionally having a few inconspicuous teeth.
M. crenata differs from M, truncata in the convex margin of its end lobes
76 BRITISH DESMIDIEiE.
and the absence of teeth on the lateral ones, but I have seen some specimens which make it doubtful whether they be really distinct.
One figure of it was engraved as the young state of M. denticulata, before reasons nearly similar to those which I have stated imder the foregoing spe- cies had induced me to describe it as distinct.
Length of frond -^^ of an inch ; breadth -g-g-g •
Tab. VII. fig. 2. and Tab. X. fig. 4. a. frond with endochrome ; b. empty frond.
**** Fronds oblong.
1 1 . ilf . Jenneri ; frond oblong, minutely granulated ; segments five- lobed, lobes closely approximate, cuneate, lateral ones obscurely bipartite, the subdivisions emarginate.
a. Granules appearing like mere puncta.
yS. Granules larger, giving a dentate appearance to the margin.
a. Greatham Bogs, Fittleworth, and Ash down Forest, Sussex, and near Southampton, Mr. Jenner. Dolgelley, J. R.
/3. Medhurst, and Ashdovra Forest, Sussex, Mr. Jenner.
Fronds large, tvdce as long as broad, oblong or quadrilateral. Segments five-lobed ; lobes cuneate, approximate, lateral ones slightly bipartite and the subdivisions truncato-emarginate. Endochrome green with scattered vesicles. The transverse view of the frond fusiform.
The surface of the frond is furnished with minute pearly granules which usually look like mere puncta, but in some specimens gathered by Mr. Jenner in Sussex they are larger and give the margin a dentate appearance.
This puzzling plant almost seems to unite Micrasterias with Euastrum. It agrees vdth the latter genus in figure, and the lobes also at first sight appear more like those of a species of Euastrum than one of Micrasterias ; but they have incisions, although mconspicuous, which divide them into two portions, each slightly emarginate. A transverse view shows the absence of the inflated protuberances always found in true species of Euastrum.
Micrasterias Jenneri differs from all other species of Micrasterias in its oblong fronds. It may easily be distinguished from Euastrum verrucosum and E. crassum by its five-lobed segments, and from E. obIon</um not only by its more quadrangular form, but by the lobes being so closely in contact as almost to conceal the separating sirmses.
Length of frond yiy of an inch ; breadth -^-i-g .
Tab. XL fig. 1. a. frond with endochrome ; b. empty frond; c. frond mag- nified 400 times ; d. transverse view.
***** Lobes horizontal, attenuated, bidentate.
12. M. oscitans (Ralfs) ; frond with convex ends ; segments con- stricted ; lobes horizontal, conical, bidentate.
Micrasterias oscitans, Ralfs, in Jenner' s FL of Tunbridge Wells, p. 198
(184.5). Holocystis oscitans, Hassal), Brit, Freshwater Algce, p. 386. t. 90. f. 4. (1845).
BRITISH DESMIDIE.E. 77
Dolgellcy, J. R. Fittleworth near Petworth, Midhvxrst, and Ashdown Forest, Sussex, Mr. Jenner. Ambleside, Mr. Sidebotham. Aberdeen, Mr. P. Grant.
West Point, New York, Bailey.
Frond smooth, nearly as large as that of Micrasterias Crux-Melitensis, and convex at its ends. Segments deeply constricted ; lobes horizontal, conical and bidentate at the apex, the basal ones longest.
The transverse view is fusiform, with two teeth at each end and a small cir- cular central opening at the connexion of the segments. Endochrome green with scattered vesicles. The empty frond is minutely pimctate.
From the resemblance of this plant to Ehrenberg's figure of young M. Ci'ux- Melitensis, I at first considered it the immature state of another species ; but haA-ing repeatedly gathered it unmixed with any species of Micrasterias to which it could belong, and Avatched it carefully for some time without detecting any alteration, I am obliged to consider it as distinct. Its size alone would forbid the supposition that it belonged to M. Crux-Melitensis ; it is thicker than any other species of Micrasterias, and finally its starch vesicles are too abmidant for a young plant. Subsequently Mr. Jenner gathered it in Sussex, and he fully agrees with my opinion that it is a cUstinct species.
Mr. Hassall, who separates it from Micrasterias, has overlooked the biden- tate extremities of the lobes, notwithstanding their presence in the Dolgelley specimens, from which his figure was taken.
Length of frond }-^ of an inch ; breadth of basal lobe -^ ; breadth of end lobe -^^.
Tab. X. fig. 2. a. frond with endochrome ; b. empty frond ; c. transverse view.
13. M. pinnatifida (Kiitz.) ; frond plane, its ends straight ; segments deeply constricted ; lobes horizontal, triangular, bidentate.
Euastrum (No. 7), Bailey, Amer. Bacill. t. 1. f. 29. (1841). Euastrum pinnatifidum, Kiitz. Phycologia Germ. p. 134. (1845).
Hab. Dolgelley, /. R. Ambleside, Mr. Sidebotham.
United States, Bailey. Germany, Kutzing. Falaise, Brebisson.
The frond is very minute and plane ; its segments are deeply constricted, and straight or slightly concave at the end. The lobes are horizontal, trian- gular and bidentate at the apex, the basal ones longest.
M. 'pinnatifida is a much smaller species than M. oscitans, but resembles it in form. Tlie surface however is flatter, the end margin is straight or slightly concave instead of convex, and the lobes are more tapering so as to appear triangular ; the colour also is paler.
I have not detected starch vesicles in this plant, and might have taken it for the young state of M. Crux-Melitensis, but its form is so similar to that of M. oscitans, that the claim of the latter undoubted species to be considered distinct would be invalidated if M. pinnatifida should be proved an immature state of M. Crux-Melitensis.
78 BRITISH DESMIDIEiE.
Length of frond j^ of an inch ; breadth at basal lobes -3^^ ; breadth at end lobes j^ ; breadth at constriction between the lobes y-gVs"- Tab. X. fig. 3. a, h. fronds with endochrome.
7. EUASTRUM, Ehr.
Frond simple, compressed, deeply divided into two segments which are emarginate at their ends, lobed or sinuated, generally pyramidal and furnished with circular inflations.
The fronds are simple, longer than broad, often oblong, compressed, and so deeply constricted that their segments seem only united by a narrow chord. The generally pyramidal segments are broadest at their bases, and are there in such close apposition for their entire breadth as nearly to conceal the notch on each side until the endo- chrome has collapsed. They are attenuated towards the ends, which in the adult state are almost always more or less emarginate, and their sides are more or less lobed or sinuated. The surface is irregular with inflated prominences, which also form tubercle-like projections along the margins ; their number and situation are, probably, constant in the adult fronds of the same species and different in distinct spe- cies. A transverse view is (when the segments are separated) the best method of ascertaining their number; the terminal lobe has similar prominences.
In Euastrum, Ehrenberg includes Micrasterias, Ag. (not Micra- sterias, Ehr.) and Cosmarium, and in this he is followed by Kiitzing in his ' Phycologia Germanica.' Meneghini separates Micrasterias from Euastrum, but includes the latter in Cosmarium. Euastrum appears to me distinct from both, and especially from Cosmarium.
Euastrum agrees with Micrasterias in having lobes and emarginate ends, but the lobes are not incised, nor do they radiate from the centre, and the inflated projections will distinguish it not only from Micrasterias, but from every other genus in the family. From Cos- marium it differs also in the lobed and emarginate segments.
I have divided this genus into three sections. In the first section the fronds are comparatively large, and appear to the naked eye like roundish or oblong dots. The segments are distinctly lobed; the terminal lobe, cuneate and itself emarginate, is partly included in a notch between the projections of the lateral lobes, and the sinuses
BRITISH DKSMIDIE^. 7^
which separate it from them are deep, and directed inwards and downwards.
In the second section the fronds are more minute and scarcely visible to the naked eye ; the segments are less decidedly lobed, but the margin is crenate or sinuated, and the terminal portion unites with the basal by a neck-like contraction of the segment, and is there- fore never "included within a notch ; the corners are rounded. The outline of a segment has some resemblance to that of a decanter or water-bottle.
The third section contains those species which do not well agree with those in the preceding ones. The fronds are extremely minute, the segments are generally still less lobed than in the last, and the form of the front view is more irregular^ and frequently differs in having a process or an acute angle at either the corners or the sides of the terminal portion.
Several species have been observed in a conjugated state.
* Segments of the frond deeply lobed; the terminal lobe cuneate, and partly included in a notch formed by the projection of the lateral lobes,
1. E. vei'rncosum (Ehr.) ; frond rough with conic granules ; the seg- ments three-lobed; lobes broadly cuneate with a broad shallow notch.
Enastrum verrucosvm, Elir. Abh. d. Bed. Ah. ^. 247 (1833) ; In/us. p, 1G2.
t. 12. f. 5. Ralfs, Atinals of Nat. Hist. v. 14. p. 189. t. 6. f. 3 ; Trans.
of Bot. Soc. of Edin. v. 2. p. 125. t. 10. liass. Brit. Alg. p. 379!
Kiitz. Phycologia Germanica, p. 135. Cosmarium verrucosum, Menegh. Synop. Desmid. in Linncea 1844, p. 222.
In pools. Cheshuut, Mr. Hassall. Weston Bogs near Soutliampton ; Rust- hall Common and elsewhere near Tunbridge Wells ; Ashdown Forest, Sussex ; Hampshire ; and Reigate, Surrey, Mr. Jenner. Penzance and Dolgelley, /. R. Near Ambleside, Westmoreland, Mr. Sidebotham. Aberdeenshire and Banff- shire, Mr. P. Grant.
Germany, Ehrenberg, Kiitzing. Falaise, Brcbisson. New York, Bailey.
Frond rather longer than broad, angular ; the segments, which slightly diverge from each other, are deeply three-lobed ; the lobes are broad, cuneate, with a broad shallow notch. Surface of the frond furnished with numerous conic granules, which give the margins a dentated appearance, especially the more prominent parts : each segment has two circular prominences near the base ; on these the granules form two or three concentric circles with a gra- nule in the centre ; the terminal lobe has two similar but smaller prominences.
80 BRITISH DESMIDIE/E.
The side view, which is not so broad as the front one, is inflated at the base, attenuated upwards into a short neck, and emarginate and shghtly dilated at the end. A transverse view is oblong, with three inflations at each side and a smaller one at each end. The terminal lobe, as seen by an end ^dew, is four-lobed.
Euastrum verrucosiim, when once seen, is not liable to be confounded with any other species, but may be known by the conic granules giving a dentate appearance to the outline.
Length of frond -g^ of an inch ; breadth -^\-^.
Tab. XI. fig. 2. a. frond with endochrome ; b. empty frond ; c. side view ; d. end view.
2. E. oblongum (Grev.) ; frond smooth, oblong ; segments five-lobed ; lobes cuneate, emarginate, the terminal one partly included between the lateral ones.
Echinella ohlonga, Grev. in Hook. Br. Fl. v. 2. p. 398 (1830).
Euastrum Pecten, Ehr. Abh. d. Berl. Ak. 1831, p. 82 ; Infus. p. 162. t. 12. f. 4. Kiitz. Phy. Germ. p. 135.
Cosmarium sinuosum, Corda, Ahn. de Carlsb. 1835, p. 121. t. 2. f. 21.
Micrasterias sinuata, Breb. Alg. Fal. p. 55. t. 7. (1835).
Cosmarium oblongum, Breb. in Menegh. Synop. Desmid. in Linncea 1840, p. 221.
Eutomia oblonga, Harv. Br. Alg. p. 188 (1841).
Euastrum oblongum, Ralfs, in Annals of Nat. Hist. v. 14. p. 189. t. 6. f. 4. (1844) ; Trans. Bot. Soc. Edin. v. 2. p. 126. t. 10. Hass. Brit. Fresh- water Alg. p. 380.
Hab. Pools ; common. Appin, Capt. Carmichael. Penzance ; Dolgelley and Carnarvon, J. R. Warbleton, Henfield, &c., Sussex ; Tunbridge Wells ; Reigate, Surrey ; and Weston Bog near Southampton, Mr. Jenner. Brook- house Moss, near Congleton, Cheshire, and near Ambleside, Westmoreland, Mr. Sidebotham. Aberdeen, Mr. P. Grant and Dr. Dickie.
Falaise, Brebisson. Germany, Ehrenberg, Kiitzing. New York ; Rhode Island and Virginia, Bailey.
Frond comparatively large, appearing to the naked eye Uke a small dot, oblong, three or four times longer than broad ; each segment divided into five lobes in a pinnatifid manner. The lateral lobes are broad, cuneate, vdth a broad shallow notch. The terminal lobe is cuneate and its notch linear ; the corners of all the lobes are rounded. The empty fronds are punctated.
The transverse view is three times longer than broad, and has three rather distant inflations or lobes on each side (the largest in the centre) and one at each end. I have not seen the end view myself, but Mr. Jenner finds the terminal lobe twice as long as broad, slightly constricted at the middle, its ends notched rather than lobed.
The sporangia are orbicular, and furnished with numerous conical tubercles ; they have been met with only near Dolgelley.
The young fronds are smaller and have the middle lobe entire.
Length of frond -—-^ of an inch ; breadth -^^ ; breadth of end lobe -g-Lg- ; diameter of sporangium ^yy ; length of tubercle -j-wo •
BRITISH DESMIDIE-<E. 81
Tab. XII. a. mature frond with endochrome ; b. empty frond ; c. mature frond of small variety ; d. transverse ^-iew ; e. transverse view of small variety ; f. end view ; g. sporangium.
3. E. a-assum (Breb.) ; frond smooth ; segments three-lobed, sub- quadrilateral ; terminal lobe cuneate, partly included in a notch formed by the lateral lobes.
Cosmarlum crassmn, Breb. in Meneyh. Sj/nop. Desm. p. 222. (1840). Euasfnim Pelta, Ralfs, in Annals of Nat. Hist. v. 14. p. 190. t. 7. f. 1. (1844),
(not Cosm. Pel fa, Corda, according to Breljisson) ; Trans. Bot. Soc. of
Edin. p. 126. Hass. Br. Fi-eshtvater Algce, p. 380. Euastrum crassum, Kiitz. Phycologia Germ. p. 135 (1845). Euastrum (No. 5), Bailey, Amer. Bacil. t. 1. f. 26.
/3. Smaller, sides more concave.
Hab. Pools ; common. Dolgelley, Penzance, /. R. Weston Bogs near Southampton ; Ashdown Forest, Sussex, and Fisher's Castle, Kent, Mr.Jenner. Ambleside, "Westmoreland, Mr. Sidebotham. Aberdeen, Mr. P. Grant and Dr. Dickie. Ben Muich Dhu and Glen Lin, Aberdeenshire, Dr. Dickie.
/5. Dolgelley, /. R.
Falaise, Brebisson. United States, Bailey. Germany, Kutzing.
Frond comparatively large, visible to the naked eye, about three times longer than broad ; of a quadrilateral form, with rounded ends ; terminal lobe cuneate, partly included between the ends of the lateral lobes, rounded and emarginate, the notch closed ; the segments of the frond are broad, three-lobed, or rather each segment has a subquadrate base and a terminal lobe. The basal portion is not attenuated, and each lateral margin has a broad shallow sinus, in which there is frequently a slight intermediate rounded projection.
The transverse view is two or three times longer than broad, with three lobes on each side and one at each end.
The empty frond is punctated.
The var. /3, regarded by Brebisson as a distinct species, is smaller, the seg- ments have more concave sides, their base is more inflated, and the angles which include the terminal lobe are more elongated.
The E. cornutum, Kiitz., diifers in having the outer angles of the lateral lobes elongated into processes.
Length of frond from ywz *° T5T ^^ ^"^ ^"^^^ 5 breadth from ^-^ to -^\^ ; breadth of end lobe g-^.
Tab. XI. fig. 3. a. frond with endochrome ; b. empty frond; c. transverse \-iew ; d. end view ; e. frond of /3 ; /". end view.
** Segments sinuated ; terminal lobe exserted and united with the basal portion by a distinct neck,
4. E.pinnatum, ; segments five-lobed ; end lobe exserted, dilated ;
upper margin of lobes horizontal.
Dolgellev, rare, J. R.
82 BRITISH DESMIDIE^.
Frond oblong, and rather smaller than that of E. ohlongum. Segments deeply five-lobed m a pinnatifid manner ; the terminal lobe is exserted, dilated and emarginate ; the basal lobes are emarginate and the intermediate ones smaller and entire ; the upper margins of all are horizontal. The transverse Aaew is oblong, with three lobes or projections on each side and one at each end. The empty frond is punctate, and the inflated projections are strongly marked.
Euastrum pinnatum somewhat resembles, but is smaller than E. ohlongum ; the terminal lobe joins the others with a distinct neck ; the intermediate lobes are always simple and smaller than the basal, and all the sinuses are more romided. There is more difficulty in separating Euastrum affine ; still, when it is compared with E. pinnatum the distinction is easily perceived, for the latter is a larger plant, and is also distinctly five-lobed ; but in the former the intermediate lobes resemble tubercles, as the sinuses between them and the basal ones are much shallower.
Length of frond y-^-g of an inch ; breadth at basal lobes ^iy ; breadth at middle lobes -^\j ; breadth at end ^-i-g- ; breadth of neck y^Vr-
Tab. XIII. fig. 1 . a. frond vdth endochrome ; b. empty frond ; c. side \aew ; d. transverse view ; e. end view.
5. E. humerosum, ; segments with terminal lobe dilated, emargi- nate; neck partly included between the elongated middle lobes, which resemble processes ; basal lobes emarginate.
Dolgelley, J. R. New Forest, Hants, Mr. Jemier.
Frond smooth, two or three times longer than broad ; segments sub-five- lobed ; the basal lobes are emarginate ; the terminal one is dilated, its notch linear, and the neck is short and partly included between the elongated pro- cesses or tubercles which represent the middle lobes. The transverse \iew has three lobes on each side and one at each end. The empty frond is minutely dotted.
Euastrum humerosum corresponds in size with E. affine, of which I formerly considered it a variety, but Mr. Jenner finds that they differ essentially in the transverse view. The present species is distinguished from all in this section by its included neck.
Length of frond -^\-g of an inch ; breadth of segment at base —^ ; breadth at end -^ki 5 breadth of neck xxrg 5 lerigtb of projections at side of neck xsVt'
Tab. XIII. fig. 2. a. frond with endochrome ; b. empty frond ; c. transverse view.
6, E. affine (Ralfs) ; segments three-lobed, with intermediate tubercles ; lobes emarginate, the end one dilated, its notch linear.
Euastrmn affine, Ralfs, A7inals of Nat. Hist. v. 14. p. 191. t. /. f. 3. (1844) ; Trans, of Bot. Soc. of E din. v. 2. p. 128. Hass. Brit. Alg. p. 382.
Dolgelley, J. R. Ambleside, Mr. Sidebotham. Sussex and Hampshire, 3Ir. Jenner. Aberdeenshire, Dr. Dickie and Mr. P. Grant.
Falaise, France, Brehisson.
BRITISH DESMIDIE.K. 83
Frond about three times as long as broad ; segments pyramidal, thrce-lobed, and ha\-ing on each side a tubercle, which replaces the middle lobes ; the end lobe is dilated and its notch linear ; the basal lobes are emarginate and sud- denly contracted beneath the tubercles, which are smaller than in the last species, and have their upper margins nearly horizontal, by which it may be distinguished from it. The transverse view also has four lobes on each side instead of three. The empty frond is punctate.
Euastnim affine differs from E. pinnatum by its smaller size, by being sinuated, not pinnatifid, and by the lobes being less prominent in the trans- verse view. In E. pinnatum we find the segments distinctly five-lobed, but in this and some other species the middle lobes are replaced by tubercles more or less developed.
Length of frond -^\q of an inch ; breadth at basal lobe -j^-g- ; breadth at middle lobes -g-|-9 ; breadth of neck ^^^^ ; breadth at end -^\j.
Tab. XIII. fig. 3. a. mature frond with endochrome ; h. empty frond ;
c. side view ; d. end view ; e. transverse view.
7. E. ampullaceum ; segments short, with inflated base, small in- termediate tubercles, and a dilated, notched, terminal lobe.
Euastrum , Hass. Brit. Freshwater Algce, t. 100. f. 11.
Dolgelley, /. R. Ambleside, Westmoreland, Mr. Sidebotham. Near Tun- bridge AVells and near Storrington, Sussex ; and Hampshire, Mr. Jenner.
Frond smooth, twice as long as broad, rather smaller than Eyastrvm affine. The base is much-inflated, and is separated from the small intermediate tuber- cles by a slight constriction. The terminal lobe is dilated, its outline usually more convex than that of the other species, and it tapers more gradually into the very short neck, hence it appears more cuneate or fan-shaped ; its notch is linear.
Euastrum ampullaceum may be best recognized by its short segments, in which and its broad inflated base it differs from E. affine, whilst the distinctly dilated terminal lobe separates it from E. Didelta.
The empty frond is punctate, and the inflated protuberances on its front surface are indistinct.
Length of frond g-fz of an inch ; breadth of base -^-j ; breadth at end y-|-g- ; breadth of neck ytt^-
Tab. XIII. fig. 4. a. frond with endochrome ; b. empty frond ; e. side view ;
d. transverse \'iew.
8. E. insigne (Hass.) ; segments inflated at the base and tapering up- wards into a slender neck ; end dilated, emarginate ; transverse view with two distant lobes on each side and one at each end.
Euastrum insigne, Hass. Brit. Alg. t. 91. f. 2. (1845).
Dolgelley, J. R. Midhurst, and Fittleworth Common near Petworth ; and New Forest, Hants, 3Ir. Jenner. Ambleside, 3Ir. Sidebotham. Moss Hagg, Banffshire (altitude 3000 feet), Mr. P. Grant.
Frond rather smaller than that of Euastnua Didelta, about three times
G
84 BRITISH DESMID1E.E.
as long as broad ; each segment is inflated at its base, the sides of which are entire, and tapers upwards into a slender neck without lateral tubercles ; ter- minal lobe dilated, its notch linear and frequently obscured by the inflated prominences. The end view is cruciform.
The transverse view differs from that of every other species, for in them the outline is elliptical, or broadest at the centre, but in this plant the sides are straight, with a little constriction at the centre and a slight swelling or lobe near each extremity ; indeed without the end lobes the form would be nearly quadrangular. The empty frond is punctate.
Mr. Sidebotham has gathered a conjugated specimen of this species near Ambleside.
The inflated base and slender neck, conjoined with its dilated end, are sufii- ciently characteristic.
To avoid a needless multiplication of synonyms, I have here adopted the name under which Mr. Hassall has figured it in his work on the British Fresh- water Algse, although in a paper read before the Botanical Society of Edin- burgh I had previously called it Euastriim gracile, and had distributed speci- mens under that name, from some of which indeed Mr. Hassall obtained his knowledge of the species, a circumstance that he has omitted to notice.
Length of frond -~^ of an inch ; breadth at base -^\-^ ; breadth at end -g^^ ; breadth of neck yx2T-
Tab. XIII. fig. 6. a. frond with endochrome ; b. empty frond ; c. side view ; d. transverse view ; e. end view.
9. E. Didelta (Turp.) ; segments vi'ith inflated base, intermediate tubercles, and notched and scarcely dilated end ; transverse view, four shallow lobes on each side and one at each end.
Heterocarpella Didelta, Turp. Mem. p. 295 (1828). Cosmarhtm Didelta, Menegh. Synop. Desmid. in Linncea 1840, p. 219. Euastrum Didelta, Ralfs, Aim. of Nat. Hist. v. 14. p. 190 (in part), t. 7. f. 2. a, b. (1844) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 127. t. II.
Common. Carnarvon, Dolgelley, Penzance, &c., J. R. Near Tunbridge Wells ; near Battle, Henfield, Midhurst, Sussex ; and Hampshire, Mr. Jenner. Westmoreland, Mr. Sidebotham. Aberdeen, Dr. Dickie and Mr. P. Grant.
Falaise, Brebisson. New York, Bailey.
Frond comparatively large, aboiit thrice as long as broad ; segments pyra- midal, inflated at the base, and tapering upwards into the intermediate tuber- cles ; the neck is broad, and the end slightly dilated, with a terminal linear notch. The end view is bilobed, and the transverse one elliptic with four slight lobes on each side and one at each end. The empty frond is punctate.
Euastrum Didelta diff'ers from the preceding species in the slight dilatation of the end lobes, and in the end view the two lobes are entire.
The sporangia, which I have twice found at Dolgelley, are orbicular, and have subulate spines.
Length of frond yig- of an inch ; breadth at base -^\^ ; breadth at end -^\-^ ; breadth at constriction Y2V0 ! thickness in side view j-|-j.
BRITISH DESMIDIEiK. 85
Tab. XIV. fig. 1 . a. frond with ondochromc ; b. empty frond ; c. transverse view ; d. end view.
10. E. ansatum (Ehr.) ; segments inflated at the base, and tapering
upwards to the notched but not dilated extremity ; transverse view
cruciform.
Euastntm aiisatum, Ehr. In/us. p. 162. t. 12. f. 6. (1838).
Euastrum , Bailey, in Amer. Journ. of Science and Arts, v. 41. p. 295.
t. 1. f. 27. (1841). Euastrum Didelta, Ralfs, Annals of Nat. Hist. v. 14. p. 190 (in part), t. 7.
f.2. c, d, e,f. (1844) ; Trans, of Bat. Soc. of Edinburgh, v. 2. p. 127. 1. 1 1. Euastrum bitiaJe, Kiitz. Phy. Germ. p. 135 (1845).
Common. North and South Wales, and Penzance, /. R. Hants, Surrey and Sussex, Mr. Jenner. Kerry, Mr. Andrews, Aberdeenshire and Banff- shire (altitudes 200-3600 feet)'. Dr. Dickie and Mr. Grant. Cheshire and Westmoreland, Mr. Sidebotham. Near Manchester, Mr. WiUiamson. Near Bristol, Mr. Thwaites. Rochdale, Mr. Coates.
France, Brebisson. Germany, Ehrenberg and K'dtzing. United States, Bailey.
Frond smaller than that of E. Didelta, twice as long as broad ; the seg- ments mflated at the base and tapering upwards into a neck, which is not dilated at the end ; the terminal notch is linear. The end view has two cir- cular and entire lobes, and the transverse view a single inflation on each side. The empty frond is pmictate.
I formerly considered this plant as the young state of E. Didelta, and I am not yet fully persuaded that it is distinct ; but as it differs from E. Didelta in every view, and Mr. Jenner, whose opinion I highly value, urges their sepa- ration, I have raised this form to the rank of a species : whether it is right to consider it one, experience must decide.
Euastrum ansatum is separated from E. circulare by the absence of the five tubercles at the base of the segments in the front view ; in respect of the other species its form is a sufficient distinction.
Length of frond g-j-g- of an inch ; breadth at base ^-L. ; breadth at end j^-g-.
Tab. XIV. fig. 2, a. frond with endochrome ; b, e. empty fronds ; d, side ■\-iew ; e. transverse \aew ; f. end view.
II. E. circulare (Hass.) ; segments three-lobed, mostly with five basal tubercles ; four of them usually disposed semicircularly about the fifth ; end notched, scarcely dilated.
a. Segments inflated at the base and attenuated upwards. Euastrum circulare, Hass. Brit. Freshwater Algce, p. 383. t. 90. f. 5. (184.5). ^. Segments emarginate at the sides, the basal portion with five tubercles. Euastrum sinuosum, Lenormand, in herb. (1845).
7. Segments emarginate at the sides ; tubercles smaller, more
numerous and scattered.
g2
86 BRIIISII DESMIDIE.E.
u. Higli Beech, Essex, HassaU. Near Aberdeen, Mr. P. Grant. (i. Dolgelley, /. R. Ambleside, Westmoreland, Mr. Sidebotham. Weston Bogs near Southampton, Mr. Jenner.
y. Ambleside, Westmoreland, Mr. Sidebotham.
^. Falaise, Brebisson.
As I have seen no authentic specimens, and am not sure whether the number and position of the inflated protuberances are constant, I may have united under this name more than one species. The variety y. especially differs from the other forms in the number and arrangement of the tubercles, but as I have seen no specimen of it, and Mr. Jenner only one or two fronds mixed with other Desmidiese, which Mr. Sidebotham forwarded from Westmoreland, I have no means of deciding where it should be placed. At the same time I am unvidlling to omit so interesting a form, and as it agrees in outline with the variety j8, I have placed it here, in the hope it may be recognized.
I have gathered near Penzance a single frond, which I suppose may be the state figured by Mr. Hassall. The protuberances were distinct on one seg- ment, but not on the other. In form it resembled E. ansatiim ; the inflations on the front surface were its most obvious chstiuction from that plant ; iu a transverse view I presume it would resemble the other varieties.
The variety /3. is not uncommon near Dolgelley ; the segments are emarginate at their sides and the end lobe is slightly dilated. On the front surface are five protuberances, but their arrangement is different from that in Mr. Hassall's figure ; they are also less distinct and sometimes scarcely perceptible. An Euastrum, however, gathered at Falaise, for the sight of which I am indebted to Dr. Dickie, unites the ft. form with protuberances exactly like those repre- sented by Mr. Hassall.
This variety agrees in some respects with Euastrum pectinatum and E. gem- matum, but has a terminal linear notch, and the end view exhibits two nearly quadrate and slightly notched lobes.
Length of frond of var. ft. -^\^ of an inch ; breadth at base g^ ; breadth of neck x^Vg '■> hreadth at end y^g-g .
Length of frond of Falaise specimen 3-L^ of an inch ; breadth at base -g\-^ ; breadth of neck , „' , : breadth at end
12 3 4' "' '-t-^^ii .^i.- v,i.^ 1149"
Tab. XIII. fig. 5. a. frond of ft. with endochrome ; b. empty frond; d. transverse view ; c. empty frond of y.
Tab. XIV. fig. 3. a. frond as figured by Hassall in Brit. Alg. ; b. frond of the Falaise variety ; c. end view.
12. E. 23eciina(um{Breh.) ; segments three-lobed; terminal lobe dilated, scarcely emarginate; lateral lobes horizontal, emarginate; end view two-lobed at each end and two lobules on each side.
ft. terminal lobe emarginate at each side.
Cosmarium pectinatum, BreT). i)i Menegh. Synop. Desmid. in Linncea 1840
p. 222. Euastrutn gemmatum, Ralfs, Annals of Nat. Hist. vol. 14. p. 191. t. 7. f. 4.
BRITISH DESMIDIE.TC. 87
(1844) ; Trons. ofBot. Soc. of Edinhnrgh, v. 2. p. 128. t. 1 1 . Ilass. Br. Alg, p. 382. (not Cosmarium gemmatum, Urcb.). Euastrum pectinatum, Br^b. in lit. cum. icone (1846).
Boggy pools ; not rare. Dolgelley, Penzance, J. B. Sussex, and Weston Bog near Southampton, 3Ir. Jenner. Brookhouse Moss, near Congleton, Cheshire ; and Ambleside, Westmoreland, Mr. Sidehotham. Glen Derry, Aberdeenshire, Dr. Dickie. Aberdeen and east of the Hill of Fare, Aberdeen- shire ; and Moss Hagg, Banffshire, Mr. P. Grant.
Falaise, France, M. De Brebisson.
Frond two or three times longer than broad ; each segment has a broad basal portion, which is somewhat quadrilateral, horizontal, and at each side emarginate ; the neck is short and broad ; the terminal lobe is dilated ; the sides entire in a. and slightly notched in ft ; the terminal notch is obsolete.
A transverse view is twice as long as broad, with three lobes on each side and two at each end.
The end view shows that the terminal portion has two lobes at each end and two lobules on each side, one belonging to each lobe. The empty frond is punctate.
Euastrum pectinatmn is a very distinct species, and differs from all the pre- cedhig in the absence of a terminal notch, in the lobules of the end lobe, and in having the ends emarginate in the transverse view.
I formerly considered this species as the Cosmarium gemmatum of Mene- ghmi's Synopsis. I am indebted to M. De Brebisson for the information that it is distinct, and also for drawings of both plants.
Sporangia gathered at Dolgelley are orbicular, with conical tubercles or short obtuse spines.
. Length of frond ^^ of an inch ; breadth at base -g\j ; breadth at end y^ ; breadth of neck y^Vj ; breadth at constriction 2-bVj > diameter of sporangium from -pio^ to -j\^.
Tab. XIV. fig. 5. a. frond with endochrome ; b. empty frond; c. frond of var. ft ; d. end view ; e. transverse view ; f. sporangium.
13. E. gemmatum (Breb.); segments three-lobed; terminailobe dilated, broadly emarginate ; basal lobes horizontal, emarginate, protube- rances minutely granulate.
Cosmarium gemmatum, Breb. Menegh. Synop. Desmid. in Linncea 1 840, p. 221 . Eiiastrmn gemmation, Kutz. Phg. Gei'm. p. 134 (1845). Breb. in lit. cum
icone. Euastrum papulosum, Kiitz. Phy. Germ. p. 135 (1845).
Bogs. Dolgelley and Penzance, J. B. Ambleside, Mr. Sidebotham. Aber- deen, Dr. Dickie and Mr. P. Grant. Weston Bogs near Southampton, and near Pulborough, Sussex, Mr. Jenner.
Falaise, De Brebisson. Nordhausen, Prussia, Kilt zing.
Frond about twice as long as broad ; segments three-lobed, the basal ones horizontal, emarginate, and their projecting parts granulated. The end lobe
88 BRITISH DESMIDIE^.
is dilated ; the neck is short, and abovit one-third as broad as the base ; the granulated dilatations of the terminal lobe are inclined upwards, hence the end is broadly emarginate. The transverse view is oblong, with three lobes on each side and one at each end. The end view shows that the terminal lobe is cru- ciform.
Euastrum gemmattim is a small but elegant species, the base being quadri- lateral, horizontal, and nearly three times as broad as long. It may be known from all in this section, except E. pectinahim, by the absence of a linear ter- minal notch, and from that species it may be distinguished by the smallness of the end lobe and the outward direction of its angles, and by the minute granulation of the projecting parts.
M. De Brcbisson has kindly furnished me with drawings of Euastrum gem- matum, BreT)., and E. papulosum, Kiitz., the latter of which he reduces to a variety of the former in a MS. list of the species of this genus ; but I must confess that I know not how to make even this distinction between them.
Length of frond ^^ of an inch ; breadth at base -^\j ; breadth at end -yttq ' breadth of neck yxgr-
Tab. XIV. fig. 4. a. frond with endochrome ; b. empty frond ; c. side view ; d. end view ; e. transverse view.
*** Frond without a distinct terminal lobe, and frequently having a process or an acute angle at the corners of the terminal portion.
14. E. rostratum (Ralfs) ; frond oblong; ends protuberant, emargi- nate and angular, with a horizontal spine on each side.
Euastrum rostrattim, Ralfs, Annals of Nat. Hist. v. 14. p. 192. t. 7. f. 5. (1844) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 129. t. 11. Hass. Brit. Alg. p. 383.
Dolgelley and Penzance, J. R. Sussex, Mr. Jenner. Near Aberdeen, Dr. Dickie and Mr. P. Grant. Moss Hagg between Tomantaul and Lochavon (alt. 3000 feet), Banffshire, Mr. P. Grant. Near Ambleside, Mr. Sidebotham.
New York, Bailey.
Frond very minute, about twice as long as broad ; segments obscurely three-lobed, or rather ha^dng a broad basal portion, which is emarginate at each side and connects itself by a broad short neck vdth the terminal lobe. This terminal portion has on each side a horizontal, subacute, beak -like process, and is prominent, emarginate and angular.
Euastrum rostratum, like the species in the preceding section, is contracted (though less decidedly) into a neck, and also has emarginate sides ; but it differs from them in its much smaller size, and especially in the horizontal processes of its end lobe. The angular and less prominent ends distinguish it from E. elegans.
A single sporangium which I gathered at Dolgelley was spinous, like that of E, elegans, but larger.
Length of frond from ^ig to g-i^ of an inch ; breadth from yoVo^ ^^ tiT-
Tab. XIY. fig. fi. n, h. fronds with endochrome.
BRITISH DKSMiniR^. 89
15. E, elegans (Breb.) ; frond oblong; ends emarginate, pouting and rounded.
a. segments slightly constricted beneath the end lobe, ^vhich has
on each side a short horizontal spine. fi.inerme; segments sinuated rather than lobed, and without spines.
y. spinosum ; segments sinuated rather than lobed, and having two or more spines directed obliquely outwards.
Cosmarium elegans, Breb. Menegh. Synop. Desmid.in Linneea 1840, p. 222. Evastrum sjnnosum, Ralfs, Annals of Nat. Hist. v. 14. p. 193. t. 7. f. 6.
(1844) ; Trans, of Bot. Soc. of Edinhurgh, v. 2. p. 129. t. 1 1. Hass.
Brit. Alg(B, p. 384. Euastrum elegans, Kiitzing, Phycologia Germanica, p. 135 (1845).
Common. Dolgelley, Carnarvon, Penzance, &c., /. R. Cheshunt, Mr. Hassall. Barmouth, Rev. T. Salwey. Near Southampton ; Reigate ; fre- quent in Sussex, Mr. Jenner. Ireland, Mr. Andrews. Hanham near Bristol, Mr. Thwaites. Yate near Bristol, Mr. Broome. Cheshire and Westmore- land, Mr. Sidebotham. Aberdeensliire and Banffshire (alt. 50 — 3000 feet), Mr. P. Grant.
Falaise, Brcbisson. Germany, Kiitzing. New York, Bailey.
Frond very minute, and about twice as long as broad ; the segments emar- ginate at their sides, and the ends protuberant, rounded and emarginate.
The sporangia are orbicular and spinous ; they have been gathered at Yate by Mr. Broome, and by myself near Dolgelley.
Euastrum elegans is a pretty but variable little species ; one state of it closely approaches E. rostratnm, with which it agrees in being somewhat contracted beneath the terminal lobe, and also in its horizontal, though smaller, spines ; but all its forms diflFer from that species by having the prominent ends not angular but rounded.
The variety /3. has no spines and no distinct neck ; the sides are undulated rather than lobed, and the ends broadly rounded.
The variety y. is distinguished by the spines bemg directed obliquely for- wards, and besides those on the terminal portion it has usually one or two at the sides ; there is no distinct neck, and the end is more protuberant and nar- row than in the other forms. The spines of its sporangia are more nume- rous and slender than those in the typal form. I have not seen sporangia from a sufficient number of stations to decide whether differences in their spines indicate different species ; but I believe that the number and shape of the spines vary even in the same species.
Length of frond of a. -g^ to -^ of an inch ; breadth y^ij^ to ^^ ; dia- meter of sporangium -^ ; length of spine of sporangium ^^j^. Length of frond of /3. ^4t ? hreadth ■^. Length of frond of y. -^ ; breadth yjLg- ; diameter of sporangium g-|-o ; length of spine -^wzx-
Tab. XIV. fig. 7. a, h, c. fronds of o. with endochrome ; d. sporangium; e. frond of var. /3 ; /. mature frond of var. y ; g. side view ; h. transverse view ; ?', A-. dividing fronds ; A sporangium.
90 BRITISH DESMIDIE^.
16. E. binale (Turp.) ; segments concave or truncate at the end ; not projecting beyond the acute angles.
Jleterocmyella binalis, Turp. Diet, des Sc. Nat. par Levr. Alt. Vey. f. 14.
(1820); Mem. du Mus. f. 17. Kiitz. Synop. Diat. in Linncea 1833,
p. 598. Breb. Alg. Fal. p. 56. t. 7. Cosmariiim binale, Menegh. Synop. Desmid. in Linncea 1840, p. 221. Euastrum binale, Ralfs, Annals of Nat. Hist. v. 14. p. 193. t. 7. f. 7. (1844) ;
Trans, of Bot. Soc. of Edinburgh, v. 2. p. 130. t. 11. Hass. Brit. Alg.
p. 384.
Penzance and Dolgelley, J. R. Henfield and elsewhere in Sussex ; Hamp- shire, and Reigate, Surrey, Mr. Jenner. Hill of Rhoil (alt. 1 600 feet), Aber- deenshire, Dr. Dickie. Near Aberdeen, Mr. P. Grant. Ambleside, Mr. Sidebotham. Near Bristol, Mr. Thwaites.
Falaise, Brebisson. New York, Professor Bailey.
Frond very minute, about twice as long as broad ; segments inflated at the base, either entire or bicrenate at the sides, slightly contracted upwards and rather dilated at the end. The terminal notch is broad, and forms a concavity between the angles.
The variety ft. (which may prove a distinct species) differs in its quadrilateral form and in its truncate ends, which have a small but distinct notch at the centre. The acute angles are slightly prolonged horizontally ; the sides of the segments are somewhat crenate, and the frond is rough, with a few scattered and very minute granules.
Euastrum biiiale is distinguished from the two preceding species by its con- cave or truncate ends and its notch, the sides of which do not project beyond the lateral spines or angles.
A solitary conjugated specimen was gathered near Bristol by Mr. Broome, but the sporangium was not completely developed.
Length of frond (Tab. XIV. f. 8. c.) y^Vs" ^^ ^^^ ^^^^^^ ' breadth ^^^. : length of frond (f. 8. d.) yyyg^ ; breadth y^g-g- : length of frond (f. 8. e.) xgVr 5 breadth 24-W: length (f. 8./.) yVor; breadth y^.
Tab. XIV. fig. 8. a, c, d, e. fronds with endochrome ; b. empty frond ; g. transverse view; h. a specimen conjugating; f. frond of var. ft.
1 7- E. cimeatum (Jenner) ; segments cuneate, not lobed ; terminal notch not linear.
Euastrum cuneatum^ Jenner, in lit. cum specimine (1846).
Aberdeenshire, Dr. Dickie. Dolgelley, J. R. Parham Old Park near Stor- rington, Sussex, Mr. Jenner.
The frond is larger than that of any other species in this section, and about three times longer than broad ; the segments are nearly quadrilateral, broadest at the base, and sloping upwards ; the ends are truncate, with a short linear notch at the centre. The sides are not sinuated, and I have not detected any inflated protuberances.
The frond has so great a. resemblance to some states of E. crassum, that, although its segments are not lobed, I think it may prove to be a variety of
BRITISH DESMIDIE^. 91
that species ; for iu Dr. Dickie's specimen I observed a frond, one segment of which answered the above descri})tion, whilst the other had a distinct, cuneate, terminal lobe, as in E. crassum. But as I lost the frond before I was able to obtain a satisfactory view of it, and as the form here described is so peculiar, aiid has been noticed in widely separated stations, I have given it the rank of a species, awaiting the result of further obsenations.
Length of frond -^^ of an inch ; breadth at base ^^-o '■> breadth of end -^.
Tab. XXXII. fig. 3. a. frond with endochrome ; b. transverse view.
18. E.} siiblobatum (Breb.) ; segments subquadrate, somewhat con- tracted beneath the end; the end margin slightly concave.
Euastriun? sublobatum, Brcbisson, in lit. cum icons (1846).
INIachpilleth and Dolgelley, North Wales, /. B. Ambleside, Mr. Side- bo f ham.
Falaise, Brebisson.
Frond twice as long as broad, and rather larger than that of E. elegans ; the segments nearly quadrate, their sides and end somewhat sinuated, and their base slightly inflated.
Euastrutn sublobatum has nearly as good a claim to a place in Cosmarium as in this genus. The terminal notch is here replaced by a slight concavity, and in their form its segments are not unlike those of Cosmariiim quadratum ; but their constricted appearance, from the more strongly-marked lateral con- cavities, inclines me to retain this species in Euastrum.
Length of frond y^r ^^ ^^^ ^^^^^ ' bi'eadth at base -^\^ ; breadth at constric- tion 3 ^^ g ; breadth of end yoVs"*
Tab. XXXII. fig. 4. a. frond with endochrome ; b. empty frond ; c. trans- verse view ; d. end view.
8. COSMARIUM, Corda.
Frond simple, constricted in the middle ; segments as broad as or broader than long, neither sinuated nor notched.
The fronds are minute, simple, constricted in the middle ; the seg- ments are generally broader than long and inflato-compressed, but in some species orbicular or cylindrical ; they are neither emarginate at the end nor lobed at the sides, and have no spines or processes.
Ehrenberg united plants belonging to this genus w^ith others having lobed segments, in order to form his genus Euastrum. Meneghini for the most part followed this arrangement, merely changing the name to Cosmarium, which had a prior claim, and also adding some species taken from Xanthidium. Under Micrasterias, Euastrum, and Xanthidium, I have given my reasons for differing from such high
92 BRITISH DESMIDIEiE.
authorities, and pointed out the characters which distinguish those genera from Cosmarium.
Both Ehrenberg and Meneghini consider the inflato-compressed segments essential; but some species with globular or cylindrical segments can by no means be separated from the compressed ones. Those having cylindrical fronds in some respects show an affinity with Penium ; but in that genus the constriction is either wanting or ob- scure, and the segments are longer than broad. In Cosmarium the fronds are never elongated, are always constricted in the middle, and the starch vesicles are scattered.
Tetmemorus differs from this genus in its elongated fronds and emarginate extremities.
The species belonging to Cosmarium may conveniently be divided into three sections.
In the first section the segments are compressed, and in the front view, which differs from the lateral one, they are united by a portion only of their bases, and thus the constriction forms a linear notch on each side. An end view is elliptic.
The plants belonging to the second section are also compressed, and, like those in the preceding, their front view differs from the lateral one and has a linear notch on each side. Each segment how- ever has a central inflation, which causes the end view to be more or less cruciform.
In the third section the end view is circular, the front and lateral views are alike, and there is no linear notch at the sides, since the segments have no constriction at their junction except that which necessarily results from their figure.
* Frond compressed, deeply constricted at the middle ; end view
elliptical. t Margin of segments entire.
1. C. quadratum (Ralfs) ; frond smooth, deeply constricted at the middle ; segments in the front view quadrate, and on each side of the base slightly protuberant.
Cosmarium quadratum, Ralfs, Annals of Nat. Hist. v. 14. p. 395. t. 11. f. 9. (1844) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 151. t. 16. Hass. Brit. Alg. p. 3G7.
Dolgelley, J. R. Rusthall Common near Tunbridge Wells, Mr. Jenner. Aberdeenshire, Br. Dickie and Mr. P. Grant.
Falaisc, Brchisson.
BRITISH DBSMIDIE/E. 93
Frond minute, constricted in the middle, the constriction forming a hnear notch on each side. The segments are compressed, and in the front view nearly square ; on each side of the base there is a slight protuberance.
C. quadratuin is smaller than C. Cucumis, and its ends are not so rounded ; but as these forms so nearly approach each other, it may prove to be merely a variety. I have however seen no intermediate state, and have therefore kept them distinct.
M. De Brcbisson informs me that at the time I described C. qiiadratum in the ' Annals of Natural History,' he had not only recognized it as distinct, but had conferred on it the same specific name.
Length of frond -^\^ of an inch ; breadth -^\-^ ; breadth at constriction from -^-^^r^ to
36 2 3 ^" 34 7 2"
Tab. XV. fig. 1 . a. front view ; b. side view ; c. empty frond of variety.
2. C. Cucumis (Corda) ; frond smooth^ deeply constricted at the middle ; segments as broad as long and rounded at the end ; trans- verse view broadly elliptic. /3. segments semiorbicular.
Cosmarium Cucumis, Corda, Aim. de Carlsb. 1835, p. 121. f. 27. Meneghini,
Si/nop. Desmid. in Linncea 1840, p. 220. Euastrum integerrhnutHy Ehr. Infus. p. 163. t. 12. f. 9. (1838), accordhig to
Meneghini. Kvitzing, Phycologia Germanica, p. 136? Pithiscus angulosus, KUtz. Phycol. Germ. p. 129 (1845).
Midhurst and Fittleworth, Sussex, Mr. Jenner. Dolgelley and Penzance, J. R. Near Bristol, Mr. Thwaites. Aberdeen, Dr. Dickie. Banffshire, Mr. P. Grant. Ambleside, Mr. Sidebotham.
Germany, Corda, Ehrenberg, Kiitzing. Falaise, Brebisson. United States, Bailey.
Frond minute, about twice as long as broad, compressed, quite smooth, constricted at the middle, the constriction forming a linear notch on each side. In a. the sides are nearly straight, except near the ends, which are rounded ; but in /3. the sides also are rounded.
C. Cucumis is smaller than C. Ralfsii ; its frond is not so orbicular, and the transverse view is different.
Length of frond from 3^ to -^^ of an inch ; breadth from -j-^-g- to -g-i-g '■> breadth at constriction from , Z, a to , „' „ .
1436
Tab. XV. fig. 2. a. front view ; b. empty frond of var. /3 ; c. transverse view.
3. C Ralfsii (Breb.) ; frond orbicular, smooth, deeply constricted at the middle; transverse view fusiform.
Cosmarium Cucumis, Ralfs, in Annals of Nat. Hist. v. 14. p. 395. t. 11. f. 8. (1844) ; Trans, of Bat. Soc. of Edinburgh, v. 2. p. 151. t. 16. Jenner, Floi-a of Tunbridge Wells, p. 196. Hass. Brit. Algce, p. 366. (Not of Corda according to Brebisson.)
Cosmarium Ralfsii, Brebisson in lit. {cum icone) (1846).
Dolgelley, ./. R. Bogs at Fisher's Castle near Tunbridge Wells ; Fittle-
94 BRITISH DESMIDIE^.
worth near Petworth, Sussex; Hampshire, &c., Mr. Jenner. Hill of Rhoil (alt. 1 600 feet), Glen Derry, Aberdeenshire, Dr. Dickie. Near Aberdeen, Mr. P. Grant.
Falaise, Brebisson.
Frond large, disciform, quite smooth, deeply constricted at the middle, the constriction forming a linear notch on each side. The segments are semi- orbicular, quite entire, and not punctate.
The endochrome is usually somewhat radiate, and the vesicles are small.
The transverse view is elliptico-lanceolate or fusiform.
This species I formerly considered to be the Euastrum integerrimum, Ehr., but M. De Brebisson has convinced me of my mistake. It is a larger plant than that figured by Ehrenberg, and more perfectly orbicular. It diifers from C Cucumis by its larger size and disciform appearance.
Length of frond from g^r to -^^ of an inch ; breadth from ^|^ to -^ ; breadth at constriction from y^Vo ^^ tAt*
Tab. XV. fig. 3. a. frond with endochrome ; h. transverse view.
4. C. pyramidatum (Breb.) ; frond oval with flattened ends, deeply constricted in the middle ; segments punctate, entire.
Cosmarium ovale, Ralfs, in An?ials of Nat. Hist. v. 14. p. 394 (in part), t. 11.
f. 7. a, b, c. (1844) ; Trans. ofBot. Soc. of Ediiiburgh, v. 2. p. 150 (in
part) ; Jenner, Flora of Tunbridge Wells, p. 196. Cosmarium pyramidatiim, Brebisson in lit. (cum icone) (1846).
Probably common. Dolgelley and Penzance, J. R. Barmouth, Rev. T. Sahvey. Near Tunbridge Wells ; Midhurst ; Henfield, &c., Sussex ; Reigate, Surrey, Mr. Jenner. Near Congleton, Cheshire, and near Ambleside, West- moreland, Mr. Sidebotham. Kerry, Mr. Andrews. Hill of Rhoil (alt. 1600 feet), Br. Dickie. Near Aberdeen, Mr. P. Grant. Near Manchester, Mr. Williamson.
Falaise, Brebisson.
Frond about twice as long as broad, varying much in size, subelliptic, with flattened ends, deeply constricted at the middle, the constriction forming a linear notch on each side.
The empty frond is punctate and entire at the margin. Transverse view broadly elliptic.
The sporangia which I have occasionally met with at Dolgelley are orbicular and tuberculated.
From Cosmarium Cucumis and C. Ralfsii this species may be known by its puncta and depressed ends. From C. ovale, with which I formerly united it, it differs in its entire margin and truncated ends. In form the segments ap- proach those of C. Botrytis, but are not granulate.
Length of frond from -^ to -^ of an inch ; breadth from yi-^ to -g^j ; breadth at constriction from g^Vr ^^ T^Vo-
Tab. XV. fig. 4. a, d. fronds with endochrome ; b. empty frond ; c, e. lateral views ; f. transverse view.
BRITISH DESM1DIE.E. 95
5. C. tinctimi ; frond smooth, constriction producing a linear
notch on each side ; segments elliptic ; integument reddish ; spo- rangium naked, subquadrate, conjugating fronds persistent.
Penzance and Dolgelley, /. R. Aslidowii Forest and Cross-in-hand, Sussex, Mr. Jenner.
Frond very minute, smooth, smaller than that of Cosmarium hioculatnm, deeply constricted at the middle, the constriction causing a linear notch on each side ; segments elliptic, twice as hroad as long, entire. The empty frond is tinged faint red or straw-colour.
The sporangium is large in proportion to the fronds, and quadrate, with an empty segment of the fronds permaaiently attached to each corner. Some- times the fronds couple in a crossed position, when the sporangium appears variously twHsted or distorted.
I overlooked this species until I gathered its sporangia near Penzance ; and indeed in the growing state it is difficult to distinguish it from Cosmai'ium bioculatum ; but it is rather smaller, the notches formed by the constriction are less gaping, and the empty fronds are slightly coloured. The sporangium however differs not only from that of C. bioculatum, but from all that I have seen.
Length of frond ^-gVr of an inch ; breadth gVoo^ '■> length of sporangium ywoI-
Tab. XXXII. fig. 7. a- front view of frond ; b. empty frond ; c. side view ; d. transverse view; e,f. conjugating fronds; g, h, i. sporangia.
6. C. bioculatum (Breb.); frond smooth, constriction producing a gaping notch on each side ; segments subelliptic, entire ; sporan- gium orbicular, spinous.
HeterocarpeUa bioculata, Brebisson, Aly. Fal. p. 5Q. t. /. (1835). Cosmarium bioculatum, Brebisson in lit. {cum icone) (1846).
Probably common. Tunbridge Wells, Henfield, &c., Sussex, Mr. Jenner. Dolgelley and Penzance, J. R. Near Bristol, Mr. Thwaites. Near Aberdeen, Dr. Dickie and Mr. P. Grant. Ambleside, Westmoreland, Mr. Sidebotham. Rochdale, Mr. Coates.
Falaise, Brebisson. United States, Bailey.
Frond very minute, about as long as broad, deeply constricted at the middle. The segments, which are elliptic, are connected by a more distinct isthmus than in the alhed species, hence there is a wdder notch on each side. The endochrome is usually more dense in the centre of each segment. The empty frond is not punctate.
The sporangium is orbicular and minute and has conical spines.
Cosmarium bioculatum differs from C. Phaseolus, Breb. in its smaller size and more elliptic segments, which are not in apposition.
Length of frond ytts of an iwch ; breadth of segment ytt^ '■> breadth at constriction ^g^^-
Tab. XV. fig. 5. a, b. front view of fronds ; c. empty frond ; d. transverse view ; e, f. sporangia.
9G BRITISH DESMIDIEJB.
7. C. granatum (Breb.) ; constriction of frond forming a linear notch on each side ; segments compressed, smooth, truncato-triangular.
Cosmarium granatum, Brebisson in lit. cum icone (1846).
Dolgelley and Penzance, very rare, /. R. Bristol, Mr. Thwaites.
Falaise, Brebisson.
Frond rather larger than those of Cosmarium bioculatum and C. Meneghinii, twice as long as broad, deeply constricted at the middle, the constriction forming a linear notch on each side ; the segments are quite smooth and entire and slope off rapidly from near the base, so that they would be trian- gular if the end were not truncate.
Not only were the few fronds that I have seen of this species of a larger size than a figure sent me by M. De Breljisson would indicate, but their segments tapered more rapidly. I have seen neither the transverse nor the end view.
This plant may be identical with Cosmarium Papilio, Meneghini.
Length of frond ^^^3^ of an inch ; breadth of segment at the base -j-gV2 > breadth of segment at the end ^ttq ' breadth of frond at constriction ^xtt*
Tab. XXXII. fig. 6. a. mature frond; b. empty frond.
ft Margin of segments crenate ; surface not granulate.
8. C. Meneghinii (Breb.) ; frond smooth, deeply constricted at the middle ; segments subquadrate, sides and end bicrenate.
Cosmarium bioculatum, Menegh. Consp. Alg. Evg. p. 18 (1837) ; Synop.
Desmid. in Linncea 1840, p. 220 {not Heterocarpella bioculata, Breb.). Euastrum bioculatum, Kiitzing, Phycologia Germ. p. 136 (1845). Cosmarium Meneghinii, Brebisson in lit. (cum icone) (1846).
Ambleside, Westmoreland, Mr. Sidebotham. Hadlow Down near May- field ; Henfield ; West Chiltington near Pulborough, Sussex ; Hants, Kent, and Surrey, Mr. Jenner. Dolgelley, J. R.
Falaise, Brebisson. Italy, Meneghini. Germany, Kiitzing. United States, Bailey.
The frond is exceedingly minute, quite smooth, and constricted at the middle, the constriction causing a linear notch on each side. The segments are nearly quadrate and the sides and end are bicrenate. The transverse view is elliptic.
Length of frond from ^-^r ^^ TsT ^^ ^^ ^^^^^ 5 breadth from xtto ^^ ttts » breadth at constriction from y-jVr to 3/59-
Tab. XV. fig. 6. a. front view ; b. empty frond ; c. transverse view.
9. C. crenatum (Ralfs) ; frond punctate, deeply constricted at the middle ; segments crenate at the margin and flattened at the end ; spines of sporangia very short.
Cosmarium crenatum, Ralfs, in Annals of Nat. Hist. v. 14. p. 394. t. 11.
BRITISH DESMIDIEJE. 97
f. 6. (1844) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 151, t. IG. Jeimer, Flora of Tunhridye Wells, p. 196. Hassall, Brit. AUj. p. 305.
Common. Weston Bogs near Southampton, and several stations in Sussex, Mr. Jenner. Dolgelley ; Penzance, &c., J. R. Hanham near Bristol, with sporangia, Mr. Thwaites. Yate near Bristol, Mr. Broome. Kerry, Mr. Andrews. Near Manchester ; and near Ambleside, il/r. (S/^eSoMayM. Craig- endanoch (alt. 1436 feet), Aberdeenshire, Dr. DicA/e. Hill of Fare (alt. 450 feet), and near Aberdeen, and in Banffshire, Mr. P. Grant.
Falaise, Brebisson.
Frond smaller than that of Cosmarium margaritiferum, twice as long as broad, deeply constiicted at the middle, the constriction causing a linear notch on each side. Segments compressed, flattened at the end and crenate at the margin, the surface punctate and even. The end view is elliptic.
The sporangia, which have been gathered abundantly at Bristol by Mr. Thwaites, are orbicular and spinous. The spines, which are very short, and in fact not longer than broad, are divided at the apex and swollen at the base.
The depressed ends distinguish this species from the next.
Length of frond -^\-^ of an inch ; breadth at constriction ^iVr 5 breadth of segment -^\^ ; diameter of sporangium -g\-^ ; length of its tubercles xoVo •
Tab. XV. fig. 7. a. mature frond ; b. empty frond ; c. sporangium.
10. C. undulatum (Corda) ; frond deeply constricted at the middle; segments semiorbicular, crenate at the margin; sporangia with elongated spines.
Cosmarium undulatum, Corda, in Almanack de Carlsbad 1839, p. 243. t. 5. f. 26.
Near Ambleside, Mr. Sidebotham. Stapleton near Bristol, Mr. Thwaites. Dolgelley, /. R. Henfield, &c., Sussex, Mr. Jenner.
Carlsbad, Corda.
Frond compressed, rather larger than that of Cosmarium crenatum, deeply constricted at the middle, the constriction forming a linear notch on each side. The segments are broader than long, crenate or undulate at the margin, the ends rounded. The crenatures are caused by ridges, which are best seen in an end view of the empty frond. The transverse view is elliptic.
Mr. Thwaites has gathered the sporangia near Bristol. They are orbi- cular, and their spines, which are divided at the apex and swollen at the base, are elongated, and in this respect differ from the last species.
It is not unlikely that some of the habitats given under Cosmai-ium crenatum may belong to this species, since I had confounded these plants mitil Mr. Thwaites' s discovery of the different sporangia.
Length of frond ^i^ of an inch ; breadth of segment -g-^ ; diameter of sporangium -j^-^ ; length of the spines of the sporangium g^^Vr-
Tab. XV. fig. 8. a, b, d. front views; c. empty frond ; e. transverse view ; f. sporangium.
P8 BRITISH DESMIDIE.E.
ttt Frond with pearly granules which give a denticulate appearance
to the margin.
11. C. tetraophthalmmn (Kiitz.) ; frond deeply constricted at the mid- dle; segments semiorbicular, rough with pearly granules which give a crenate appearance to the margin.
Heterocai'pella tetrophthalma, Kutzing, Si/nop. Diatom, in LinncBu 1833,
p. 597. f. 87. Brc'bisson, Alg. Fal. p. 56. t. 7. Cosmariiim ovale, Jenner, Fl. of Tunbridge Wells, p. 196 (1845). Euastrum tetrophthalmum, Kiitz. Phy. Germ. p. 136 (18-15). Cosmarium tetraophthaltman, Brebisson in lit. (1846) ; not of Meneghini
according to Brebisson.
Probably common. Penzance ; Dolgelley ; and near Carmarthen, J. R. Sussex ; Hants ; and Surrey, Mr. Jenner. Near Bristol, Mr. Thioaites. Near Ambleside, Westmoreland, Mr. Sidebotham. Aberdeen, Mr. P. Grant.
Germany, KUtsing. Falaise, Brebisson.
Frond compressed, longer than broad, larger than that of Cosmariian margaritiferum, and deeply constricted at the middle, thus acquiring a linear notch on each side. The segments are semiorbicular, or more usually two- thirds of a circle. The pearly granules, by their roundness, produce at the margin a crenate rather than a dentate appearance. The transverse view is broadly elliptic.
Cosmarium tetraophthahnum may be distinguished from C. RaJfsii and C. pyramidatmn by its dentated margin, and from C. ovale by its differently- shaped frond and its scattered granules. The pearly granules are, in their form, unlike those of C. Brebissonii. It is a lai'ger plant than C. margariti- ferum, and has also a more rounded margin.
Its sporangia have been gathered by Mr. Thwaites ; they are large and their spines finally branched.
Length of frond ^ig of an inch ; breadth of segment -^^ ; thickness m side view -^^ ; diameter of sporangium ji-j ; length of spines of sporangium 2TT2 •
Tab. XVII. fig. 11. a. front view of mature frond; b. empty frond; c. transverse view. Tab. XXXIII. fig. 8. sporangium with empty fronds attached.
12. C. ovale (Ralfs) ; frond elliptic, deeply constricted at the middle; segments with a marginal band of pearly granules, the disc punctate.
Euastrum,, No. 6, Bailey, Amer. Bacil. in Amer. Journ. of Science and Arts,
V. 41. p. 295. f 28. Cosmarium ovale, Ralfs, in Annals of Nat. Hist. v. 14. p. 394. t, 11. f. 7.
d, e. (1844) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 15. t. 16.
Hassall, Brit. Algee, p. 366. Euastrum carinatum, Ehr. (Professor Bailey in lit. 1846).
Weston Bogs near Southampton, Mr. Jenner. Ambleside, Westmoreland, Mr, Sidebotham.
West Point, New York, Bailey. Falaise, Brebisson.
BRITISH desmidie>t:. 99
Frond large, oval, tviice as long as broad, deeply constricted at the middle ; the apposition of the segments for their entire breadth ren<lers tlie notch on each side Imcar ; the pearly granules are large and confined to the margin, where they form three to six series, the largest and central row producing a dentate appearance ; the rest of the frond is merely punctate.
The endochrome of each segment is often longitudinally divided by a pale line. The transverse view is elhptic.
Cosmarium ovale is one of the largest species in the genus ; its oval form and its disc devoid of granules sufficiently characterise it.
Length of frond yig of an inch ; breadth of segment -^-^ ; breadth of con- nectmg portion y-L.
Tab. XV. fig. 9. a. front view of empty frond ; b. side view.
13. C. Botrytis (Bory) ; frond granulate, deeply constricted ; seg- mentSj in the front view, truncato-triangular ; end view elliptic.
Heterocai'peUa Botrytis, Bory, Diet. Class, t. 8 (1825).
Cosmarium deltoides, Corda, Aim. de Carlsb. 1835. p. 120. f. 18.
Euastrum Botrytis, Ehr. Infus. p. 163 (1838). Kiitz. Phy. Germ. p. 13G.
Euasti'um angulosum, Ehr. Infus. t. 10. f. 8 (1838).
Cosmarium Boti'ytis, Meneghini, Synop. Desm. in Linnaea 1840, p. 220.
Ralfs, in Annals of Nat. Hist. v. 14. p. 393. t. 1 1. f. 5 ; Trans, of Bat.
Soe. of Edinburgh, v. 2. p. 15. t. 16. Hassall, Brit. Alg. p. 363.
Dolgelley and Penzance, /. R. Bristol, Mr. Thwaites. Bexhill, &c., Sussex, Mr. J(??««e/*. Manchester; and Ambleside, Ji/-. *S'/</f'6oMffw^ Essex, Mr. Hassall. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Banffshire, Mr. P. Grant.
Germany, Ehrenberg. Falaise, Brebisson.
Frond compressed, more or less rough with pearly granules, which give a denticulate appearance to the margin, deeply constricted at the middle, the constriction forming a linear notch on each side. In the front view the seg- ments are broadest at the base and gradually narrower towards the end, which is trmicated ; hence their figure is somewhat angular. The transverse view is elliptic.
The pearly granules are sometimes very evident, sometimes obscure, but they can always be detected at the margin by the higher powers of the mi- croscope.
Mr. Thwaites has gathered a single sporangium near Bristol ; it was orlji- cular, its spines elongated and slightly divided at the apex.
Cosmarium Botrytis may be known from C. margaritiferum by its trmicate ends ; and from C. pyramidatum by its more triangular segments and denti- culate margins.
Length of frond from -j^ to -giy of an inch ; breadth at constriction o^Vo to YxTB" 5 breadth of segment -g-ig- to j J-g ; diameter of sporangium -^^ ; length of spines of sporangium ^ /^ ^ .
Tab. XVI. fig. 1. a. mature frond; b. empty frond; c. transverse view; d. sporangium with empty fronds attached.
H
100 BRITISH DESMIDIEiE.
14. C. margaritiferum (Turp.) ; frond rough with pearly granules, which are as broad as long ; segments semiorbicular or reniform ; end view elliptic.
«. Segments semiorbicular.
/3. reniformis ; segments reniform.
Ursinella margaritifera, Turp. Diet, des Sc. Nat, f. 23 (1820) ; Man. du
Mus. p. 295. t. 13. f. 19. Cijinbella reniformis, Ag. Consp. Diatom, p. 10 (1830). Leibl. FI. 1830,
p. 315. t. 1. f. 2. Gre\ille, in Hook. Br. FL v. 2. p. 415. Harvey,
Brit. Aly. p. 215. Heterocarpella Ursinella, Kiitzing, Synop. Diatom, in Linncea 1833, p. 598. Euastrum. margaritiferum, Ehr. Ahh. der Berl. Ak. 1833, p. 246 ; Infus.
p. 163. t. 12. f. 7. Kiitzing, Phycol. Germ. p. 136. Bailey, Amer.
Journ. of Science and Arts, v. 41. p. 295. f. 8. Micrasterias margaritifera, Brebisson, Alg. Fal. p. 55. t. 7 (1835). Cosmarium margaritiferum, Meneghini, Synop. Desmid. in Linncea 1840,
p. 219. Ralfs, in Annals of Nat. Hist. v. 14. p. 393. t. 11. f . 4 ;
Trans, of Bot. Soc. of Edinburgh, v. 2. p. 15. t. 16.
Very common. Dolgelley ; Carnarvon; near Carmarthen ; Penzance, &c., J. R. Barmovitli, Rev. T. Salwey. Sussex ; Kent ; Surrey ; and Weston Bogs near Southampton, Mr. Jenner. Farnham, Surrey, Mr. Reeves. Herts, Mr. Hassall. Near Bristol, Mr. Thwaites and Mr. Broome. Kerry, Mr. Andrews. Near Manchester, Mr. Gray. Cheshire and Westmoreland, Mr. Sidebotham. Aberdeenshire and Banffshire, Dr. Dickie and Mr. P. Grant. Rochdale, Mr. Coates.
Germany, Leiblein, Ehrenberg and Kiitzing. Falaise, Bi'ebisson. West Point, New York ; and in Mexico, Bailey.
Frond compressed, deeply constricted at the middle, the constriction causing a linear notch on each side. The segments are broader than long, semiorbi- cular or reniform, and rough with pearly granules, which are as broad as long, and give a dentate appearance to the outline. The transverse view is elliptic.
The sporangia of this species, which I have gathered at Dolgelley, are or- bicular and inclosed in a granulate cell, which is usually somewhat angular.
Cosmarium margaritiferum varies in size and form. The rough frond distinguishes it from C crenatum and C undulatum ; its rounded ends from C. Botrytis ; its smaller size and shorter granules from C. Brebissonii, and its less angular shape from C. conspersum.
Length of frond from g-J-g- to -3^^ of an inch ; breadth from -g-i^ to -^^-^ ; diameter of sporangium yiy ; length of spines of the sporangium -2-2V3 '■> length of swollen base of spine ygVg •
Tab. XVI. fig. 2. a. var. /3 ; b. empty frond of a ; c. transverse view; d. sporangium vdth empty segments of conjugated fronds. Tab, XXXIII. fig. 3. a, b. mature sporangia.
15. C. Brebissonii (Menegh.) ; frond rough with conic spines or granules ; segments semiorbicular ; end view elliptic.
Cosmarium Brebissonii, Meneghini, Synop. Destnid. in Linncea 1840, p. 219.
BRITISH DESMIDIE.E. 101
Piltdown Common ; Midliurst ; Aslulowii Forest, near Tunbridge Wells, &c. ; Hampshire ; Sussex ; Reigate, Surrey, Mr. Jenner. Dolgelley, /. R.
Falaise, Brebisson.
Frond compressed, larger than that of Cosmarimn margaritiferiim, deeply constricted at the middle, the constriction producing a linear notch on each side. Segments rather broader than long, semiorbicular, rough with pearly granules or spines, which are longer than broad. The transverse view is elliptic.
I am not sure that this form is sufficiently distinct from Cosmarii/m mar- garitiferum, as the specific difference chiefly depends on the elongated pearly granules, a character which. I fear is inconstant.
Our specimens do not agree exactly with a drawing sent me by M. De Bre- bisson ; but in specimens received from him the spines are less crowded than in his figure. He informs me that " Le Cos. Brebissonii est plus globuleux que le C. inargaritifenim, et herisse de papilles inegales plutot que de tu- bercules*."
Length of frond -g-i-g- of an inch ; breadth of segment j^ ; length of mar- ginal spine -^-^.
Tab. XVI. fig. 3. a. empty frond ; b. side view.
16. C.conspersum ; frond rough with depressed granules ; seg- ments quadrilateral; end view elliptic.
Dolgelley, J. R. Henfield, Mr. Jenner.
Frond compressed, larger than that of Cosmarimn margaritiferum and having at the middle a deep constriction, which makes a linear notch on each side ; segments rather broader than long, quadrilateral, rough with pearly granules, which give a dentate appearance to the outline. The transverse \-iew is elliptic.
Cosmarmm conspersum differs from C. margaritiferum and C. Brebissonii in its quadrilateral figure and in having its granules (which are more depressed than those of C. Brebissonii) arranged in lines. In the front view its form is not unlike some states of C. biretum ; but in that species the granules are smaller, and the end margin is more prominent and generally flattened at the centre.
I formerly considered this plant to be the C. Brebissonii, with Meneghini's description of which it certainly agrees better than a specimen so named which has been sent me by M. De Brebisson.
Length of frond -g-g-g of an inch ; breadth at constriction -^^ ; breadth of segment 3!^.
Tab. XVI. fig. 4. a. empty frond ; b. transverse view.
* I add Meneghini's characters of the two species : — " C. margaritiferum, cellulis e dorso ellipticis, e latere semiorbicularibus, su-
perficie granulato-margaritifera." " C. Brebissonii, celluhs e dorso elongato-ellipticis, e latere introrsum curvatis, formam trapezii prae se ferentibus, superficie granulato-margaritacea."
h2
102 BRITISH DESMIDIE^.
17- C. amcenum (Br^b.) ; frond twice as long as broad, with parallel sides and rounded ends, deeply constricted at the middle, rough with pearly granules.
Cosmarium amcenum, Brebisson, in lit. cum icone (1846).
Ambleside, "Westmoreland, Mr. Sidebotham. Dolgelley, J. R. Falaise, Brebisson.
Frond smaller than that of Cosmarium margaritiferum, twice as long as broad, deeply constricted at the middle, the constriction causing a linear notch on each side ; the sides nearly straight and the ends roimded. Segments cam- panulate, rough with crowded, obtuse, pa])illa-like, pearly granules which give a dentate appearance to the margin. The side view is narrower and about thrice as long as broad.
In form, Cosmarium amcenum resembles the cylindrical species rather than the compressed ones with which it is here classed ; but its smaller size and nearly parallel sides will distinguish it from the other species of the latter, whilst from the former it may be known, in the front view, by the linear notch which the constriction produces on each side.
Length of frond 3-^ of an inch ; breadth at constriction yaTo '■> breadth of segment ^J^.
Tab. XVII. fig. 3. a. mature frond ; b. empty frond ; e. side view.
** Constriction, in the front view, forming a linear notch on each side ; end view with a lobe or protuberance on each side.
t Frond rough with pearly granules.
18. C. biretum {Bxeh.) ; segments compressed, quadrilateral, broadest at the end ; the end margin convex, slightly truncate at the middle ; end view with a lobe on each side.
Cosmarium biretum, Brebisson, in lit. cum icone (1846).
Hastings and Bexhill, Sussex, Mr. Jenner.
Falaise, Brebisson.
Frond larger than that of any other species in this section, deeply con- stricted at the middle, the constriction forming a linear notch on each side. The segments are compressed, quadrilateral or somewhat hexagonal, nearly twice as broad as long, narrowest at the base and gradually dilated upwards. The end margin, which is the longest, is more convex in Sussex thau in French specimens, and becomes angular from being slightly flattened at the middle.
The empty frond appears punctate rather than granulate.
An end view is slightly inflated at the middle. The inflation in this and the two foUovnng species depends upon a central protuberance of the segment, similar to that observable in some species of Xanthidium, and in this respect
BRITISH DESMIDIEiE. 103
differs from tlie inflation of Cosmarlum ornatnm and C. commissurah, in which plants it is longitudinal, and extends to or heyond the end margin.
From all except Cosi/iariian Bi-oomeii, this species is known by its qua- drangular segments, the lateral margins of which are sloi)ed, not rounded. From that species it differs in its larger size, more distinct angles, and the greater comparative length of the end margin, which is also convex and slightly angular, whilst in C. Broomeii it is nearly straight.
Length of frond -3^3^ of an inch ; breadth at constriction -^ 3'^ g ; breadth of segment -^\-^.
Tab. XVI. fig. 5. a. Sussex specimen ; b. empty frond of French specimen ; e. end view.
19. C. Broomeii (Thwaites) ; segments compressed, minutely gra- nulate, quadrilateral ; end view slightly inflated at the middle.
Cosmariiim Broomeii, Thwaites, in lit. cum specim. (1846). In brackish water at Sliirehampton near Bristol, Mr. Broome and Mr. Thwaites. Piltdown, Sussex, Mr. Jenner.
Frond as large as that of Cosmarium margaritiferum, deeply constricted at the middle, the constriction forming a linear notch on each side. The seg- ments are compressed, minutely granulate, quadrilateral, and twice as broad as long ; the end margin is straight.
The end view is twice as long as broad, slightly inflated at the middle and broadly rounded at the ends. In the transverse view the inflation is greater, and there is a slight constriction between it and the ends.
Cosmarium Broomeii resembles in the front view some states of C. marga- ritiferum, but differs in the end one. The inflation does not project at the margin in the front view, as in C. ornatum, and the lateral margins are less rounded, the pearly granules are also smaller.
Length of frond -^ of an inch ; greatest breadth -^ ; breadth at con- striction Yxo" '■> thickness at the inflation in end view gi^- ; least thickness in the end view yttT' Diameter of sporangium -5^.
Tab. XVI. fig. 6. a. frond with endochrome ; b. empty frond ; c. end view; d. transverse \aew. Tab. XXXII. fig. 7. sporangium.
20. C. calatum ; frond suborbicular ; segments crenate, rough
with pearly granules ; end view slightly inflated at the middle.
Near Machynlleth, North Wales, /. R. Tunbridge Wells and AshdowTi Forest, Sussex, Mr. Jenner. Falaise, Brehisson.
Frond nearly orbicular, scarcely so large as that of Cosmarium margari- tiferum, compressed, constricted at the middle, the constriction causing a linear notch on each side. The segments are scolloped or broadly crcnate : each segment has six crenatures, four at the end, one at each side and one at each intermediate angle, the lateral ones being the largest, whilst between all the
104 BRITISH DESMIDIE-iE.
crenatures the margiii is somewhat suleated. The pearly granules are distinct, especially on the crenatures, to which they give a dentate appearance. The end view is slightly cruciform, and the transverse view still more so. The lateral view is constricted at the middle and emarginate at the ends.
Cosmariiim ccelatum is a very distinct species and requires no comparison with any other.
Length of frond from -^\^ to y^y of an inch ; greatest breadth from yo^ to ^-i-g- ; breadth at constriction from ^^^3;^ to y-gV?"'
Tab. XVII. fig. 1. a. frond with endochrome ; b. empty frond; c. empty frond of Sussex specimen ; d. dividing frond ; e. side view ; /. end view ; g. transverse view.
21. C. ornatum (Ralfs) ; segments twice as long as broad, rough with pearly granules which give a dentate appearance to the margin ; inflation forming a truncate projection at the end ; end view cru- ciform .
Cosmarium ornatum, Ralfs in Annals of Nat. Hist. v. 14. p. 392. t. 11. f. 3 (1844); Trans, of Bot. Sac. of Edinburgh, v. 2. p. 148. t. 16. Jenner, Fl. ofTimbridge Wells, p. 194. Hassall, Br. Alg. p. 364.
Cosmarium Sport el I a, Brebissou, MS.
Not uncommon. Dolgelley ; Barmouth ; and Penzance, J. R. Ashdown Forest, &c., Sussex, and Weston Bogs near Southampton, 3Ir. Jenner. Ches- hunt, 3Ir. Hassall. Kerry, Mr. Andreivs. Ben Muich Dhu (alt. 2800 ft.) ; Linn of Dee (1190 ft.); Little Craigendall, Braemar, Aberdeenshire, Dr. Dickie. Aberdeen, Mr. P. Grant. Ambleside, Westmoreland, Mr. Side- botham.
Falaise, Brebisson. West Point, New York, Bailey.
The frond is generally smaller than that of Cosmarium margaritiferum and deeply constricted at the middle ; the constriction forms on each side a hnear notch, which is nearly closed by the apposition of the segments. The seg- ments are compressed, about twice as broad as long, and rough with pearly granules which give a dentate appearance to the margin. The inflation ex- tends beyond the margin in a truncate projection, and in the end view forms a rounded lobe on each side, prodvicing a cruciform figure.
Cosmarium ornatum differs from the other species by its inflation extending into a truncate projection beyond the margin.
The sporangium has been found near Bristol by Mr. Broome, and I have gathered it at Penzance. Its spines are elongated, slightly divided at the extremity and dilated at the base.
Length of frond -^\^ of an inch ; greatest breadth -^\^ ; breadth at con- striction a-oTTJ diameter of sporangium -^\-g; length of spine of spo- rangium T-sVa .
Tab. XVI. fig. 7. a. front view of mature frond ; b. empty frond ; c. end view ; (/. transverse view ; e, sporangium.
BRITISH DESMIDIE^. 105
22. C. commissurale (Br^b.) ; segments narrow-reniforrrij three times broader than long, rough with pearly granules ; end view with a constriction between the central inflation and the extremities.
Cosmarium commissurale, Brcbisson. Meneghini, Synop. Desmid. in Linncea 1840, p. 220. Brcbisson, iti lit. cum icone.
Piltdowii Common, Sussex, Mr. Jenner. Near Penzance, J. R. Near Bristol, 3Ir. Thwaites.
Falaise, Brcbisson.
Frond smaller than that of any other species in this section, broader than long, very deeply constricted at the middle. The segments are compressed, three times as broad as long, reniform, sometimes inclining to triangular in consequence of the projection of the inflation at the margin ; they are rough with pearly granules which give a dentate appearance to the outline. The transverse view is three times longer than broad, vrith a constriction between the central inflation and the rounded ends.
The sporangia have been gathered very sparingly by INIr. Jenner. They are orbicular, with slender, elongated spines, which are slightly di\'ided at the apex and dilated at the base.
Tlie great breadth of the frond compared with its length and the reniform segments well distinguish this species.
Length of frond -^^ of an inch ; greatest breadth -^\^ to -g-ig^ ; breadth at constriction yiVs" » thickness of central inflation m end view y\TT '■> diameter of sporangium y^ ; length of spine of sporangium yaV^*
Tab. XVI. fig. 8. a. front view of frond; b. empty frond; c. transverse view ; d. sporangium.
23. C. cristatum ; frond orbicular, deeply constricted at the
middle, margined by papilla-like pearly granules ; end view linear, with an inflation at the middle of each side.
Ambleside, Westmoreland, Mr. Sidebotham.
Frond exactly orbicular, much compressed, deeply constricted at the middle, the constriction formmg a linear notch on each side ; the segments margined hy a series of obtuse, papilla-like, pearly granules. At the centre of each segment is a circular granulate inflation. The end view is nearly linear, with truncate ends and an inflation on each side at the middle.
The above description is founded on Mr. Jenner's notes and drawings. I have not seen this plant, but have no doubt that it is a good species.
Length of frond -g-^-g of an inch ; greatest breadth ^^ ; breadth at con- striction XT&5'
Tab. XVIL fig. 2. a. front view of mature frond ; b. empty frond ; c. end view.
106 BRITISH DESMIDIE^.
tt Frond smooth.
24. C. Phaseolus (Breb.) ; segments smooth, reniform ; constriction forming a linear notch on each side ; end view elhptic witha shght projection at the middle of each side.
Cosmarium Phaseolus, Brebisson, in Menegh. Synop. Desmid. in Linneea 1840, p. 220. Breljisson, in lit. cum icone.
Dolgelley and Penzance, J. R.
Falaise, Brebisson.
Frond larger than that of Cosmarium biocidatum, deeply constricted at the middle, the constriction forming a linear notch on each side ; segments twice as broad as long, reniform, quite smooth and entire. The end view is elliptic and shows on each side a slight conical inflation, resembling that seen in Xanthidium fascicidaUun.
The small circular inflation which is present at the centre of each segment compels me to associate this with the other inflated species ; but it differs from all of them in its smooth fronds, and the slight inflation can be detected only by an end view. Cosmarium Phaseolus is far more likely to be mistaken for C. biocidatum, and indeed is placed next it by Brebisson ; but it is larger, its segments are reniform, not elliptic, and the notches caused by the con- striction are not gaping as in that species.
Length of frond yiy of an inch ; breadth g-i-g ; breadth at constriction -^-^j-g.
Tab. XXXII. fig. 5. a. front view ; b. empty frond; e. end view.
*** Constriction not forming linear notches at the sides ; end view
circular. t Frond rough with pearly granules which give a denticulate appear- ance to the outline.
25. C. cylindricum (Ralfs) ; segments granulated, subquadrate in the front view, broadest at the extremity ; end view circular.
Cosmarium cylindricum, Ralfs, Annals of Nat. Hist. v. 14. p. 392. t. 11. f. 1 (1844) ; Trans, of Bot. Soc. 'of Edinburgh, v. 2. p. 148. t. 16. Jenner, Fl. of Tunbridge Wells, Suppleinent, p. 18. Hass. Br. Alg. p. 3G5.
Wet sides of a cave at Lamorna Cove near Penzance, and wet sides of a cliff" at Machynlleth, North Wales, J. R. Ashdown Forest ; near Tunbridge Wells, and near Battle, Mr. Jenner.
Frond minute, cylindrical, about twice as long as broad. The subquadrate segments are broadest at the extremity, which is truncate, somewhat tapering towards the junction, and rough with pearly granules which give a dentate appearance to the outline.
Cosmarium cylindricum may be known from C. Cucurbita by the condition of its segments described above.
Length of frond j-i-g- of an inch ; greatest breadth yoVo ^ hreadfh at con- striction ytjVt-
Tab. XVII. fig. 4. a. mature frond; b. empty frond ; c. end view.
BRITISH DESMIDIE^. 107
26. C. orbiculatum (Ralfs) ; segments spherical, rough with pearly granules.
Cosmarium orhicvlahtm, Ralfs, Ann. of Nat. Hist. v. 14, p. 392. t. 11. f. 2 (1844) ; Trans. ofBot. Soc. of Edinburgh, v. 2. p. 148. t. 16. Hass. Br. Alg. p. 364.
Dolgelley, /. R. Midhurst, Sussex, Mr. Jenner. Ambleside, Westmore- land, Mr. Sidehotham.
Falaise, Brcbisson.
Frond minute, composed of two spherical segments, rough with pearly gra- nules, giving a dentate appearance to their outHnes, but wanting on the neck- hke contraction between them. The transverse view has a large central opening.
Cosmarium orbiculatum varies in size ; the larger specimens somewhat re- semble the lateral view of Cosmarium margaritiferum ; the front view how- ever of that species differs in the shape of the segments and in the presence of a linear notch on each side at their junction. The granulated fronds distin- guish it from the following species ; its central opening also is much larger.
Length of frond from -j^ to jig- of an inch ; greatest breadth from yiy to yJ-g ; breadth at constriction yxrg 5 diameter of sporangium -g-^ ; length of
Tab. XVII. fig. 5. a. mature frond ; b. empty frond ; c. transverse view. Tab. XXXIII. fig. 9. sporangium.
tt Frond smooth.
27. C. moniliforme (Turp.) ; segments spherical, smooth.
a. Segments united without the intervention of a neck. /3. Segments united by a distinct neck.
Tessarthronia moniliformis, Turp. Diet, des Sc. Nat. t. 7. f. 1.? (1820). Tessarthra moniliformis, Ehr. Abh. d. Berl. Ak. 1835, p. 1/3 ; Infus. p. 145. t. 10. f. 20.
a. Dolgelley ; rare ; ./. R. Charlton Fields near Manchester, Mr. Side- botham. Ashdown Forest ; Fittleworth ; and Rackham Bogs near Pulborough, Sussex, Mr. Jenner.
ft. Penzance.
Germany, Ehrenberg .
The frond is small and quite smooth. In a. each segment is a perfect globe, ha^ang a very small opening through which it connects with its fellow. Their appearance is one of mere juxtaposition, and their junction can only be ascer- tained and the opening seen in a transverse Adew. This state is liable to be mistaken for a not micommon plant with two globular cells, which I consider to belong properly to the Palmellese, and to be the Scenedesmus moniliformis of Kiitzing's ' Phycologia Germanica' and Brebisson's 'Alg. Fal.,' as also the Trochisciu moniliformis of Meneghmi's ' Synopsis Desmidiearum.' The resem- blance indeed is at times so complete that I have occasionally been puzzled to distinguish them ; but in specimens of the latter some individuals may gene-
108 BRITISH DESMIDIEiE.
»
rally be perceived which have a slight interval between the globes, whilst its solitary globes are filled with endochrome. In Cosmariiim moniliforme, as the globes are united they are in close contact, and when separated their con- tents escape at the orifice.
Both Kiitzing and Meneghini refer to the Tessarthra moniliformis as iden- tical with the plant described by them under the names mentioned above, but I have no hesitation m considering that it is the present plant. Ehrenberg's figure, which exhibits a frond dividing and forming two smaller globes between the original ones, appears to me decisive of the question. M. De BreTaisson concurs in this opinion, that the Tessarthra moniliformis, Ehr., is not the Trochiscia moniliformis of Meneghini's ' Synopsis.'
The var. /3. resembles more nearly the form of Cosmarium orbiculatum, from ha^nng, like that species, a distinct connecting neck ; but its fronds are quite smooth and without granules or puncta.
Length of frond -^^y ^^ ^^ "^^^^^ 5 greatest breadth ^^^3^ ; breadth at con- striction -2tVo •
Tab. XVII. fig. 6. a. usual state ; b. variety /3 ; c, d. dividing fronds ; €. empty frond ; /. transverse view.
28. C. connatum (Breb.) ; segments punctate, each about two-thirds of a circle, uniting by their plane surfaces ; end view circular.
Cosmarium connatum, Breb. in lit. {cum icone) (1846). ■
Ambleside, Westmoreland, Mr. Sidebotham. Dolgelley, /. R. Falaise, Brebisson.
This is one of the largest species in the genus. The fronds are nearly twice as long as broad, and slightly constricted at the middle. In the front view the segments are broader than long ; one-third of the margin is interrupted by their broad junction, and the remainder constitutes two-thirds of a circle ; a distinct border is always present, and often appears striated.
The empty frond is punctate rather than granulate, and the end view is circular.
With a little attention this species is easily recognized. Its very broad junction without lateral incisions distinguishes it from those species which have compressed fronds, and its large size and segments broader than long from those which have a circular end view. Its aspect in the front \'iew is more like that of Staurastrum tumidum, but the latter has more elliptic segments, and generally shows one at least of its nipple-like angles.
Length of frond -^^ of an inch ; greatest breadth yy xr 5 breadth at con- striction y^Vq*
Tab. XVII. fig. 10. a. mature frond; b. empty frond.
29. C. Cucurbita (Breb.) ; frond punctate, slightly constricted at the middle and rounded at the ends ; transverse view circular.
Cosmarium Cucurbita, Breb. in Desm. Alg. No. 1103 (184 ). Ralfs, Annals of Nat. Hist. V. 14. p. 305. t. 1 1. f.' 10 ; Tra7ts. nfBot. Soc. of Edinb.
BRITISH DESMIDIEiC. 109
V. 2. p. 1 j1. t. 16. Jenncr, FL ofTunhridge Wells, p. 196. Hass. Br. Alff. p. 367. Closterium clandesthnm, Kiitz. Phy. Germ. p. 132 (1845). (Kutzing in lit.)
Rather common. Dolgelley ; near Lampeter ; and Penzance, J. R. Ash- down Forest, Grcatham Bogs near Pulborough, Sussex ; and near Southampton, Mr. Jenner. Near Bristol, Mr. Thwaites. Near Congleton, Cheshire ; and Ambleside, Westmoreland, Mr. Sidebotham. Kerry, Mr. Andrews.
Falaise, Brcbisson. Germany, Kutzing. ^
The frond is minute, subcylindrical, twice as long as broad, with a very slight constriction at the middle, and rounded at the ends. The transverse view is circular, with a large opening.
Cosmarium Cucurbita agrees in size with C. cglindrieum, but is punctate, not granulate. The segments differ also in figure from those of that plant, and resembling two cupping-glasses with their mouths m contact, are aptly charac- terized by the specific name.
Length of frond -^-^ of an inch ; greatest breadth yttj > breadth at con- striction YXTg.
Tab. XVII. fig. 7. a. front view of mature frond ; b, c. empty fronds ; d. transverse \'iew ; e. dividing frond.
30. C. Thivaitesii ; frond cylindrical, constricted at the middle
and rounded at the ends ; puncta very indistinct.
Bristol, Mr. Thwaites. Swansea, /. R.
Frond two to three times longer than broad, larger than that of Cosmarium Cucurbita, which in form this species much resembles ; sides parallel, the middle slightly constricted and the ends broadly rounded. Mr. Jenner finds ver)^ faint, minute, scattered puncta after the escape of the endochrome. Mr. Thwaites' s specimens were very gelatinous, but I was unable to ascertain whether each plant had a distinct mucous covering, or was merely imbedded in a common matrix. The transverse \'iew appears to me cyhndrical, but Mr. Jenner finds the segments slightly compressed.
Cosmarium Thwaitesii differs from C. Cucurbita in its larger size and in- distinct puncta ; from C. curtum in its differently arranged endochrome ; and from C. turgidum and C. attenuatum in its nearly parallel sides.
Length of frond ^^y of an inch ; greatest breadth -g-^ ; breadth at con- striction -g-L.
Tab. XVII. fig. 8. a. fronds surrounded with gelatine ; b. empty frond ; c. transverse view.
31. C. curtum (Breb.) ; frond oblong, constricted at the middle and rounded at the ends ; endochrome in longitudinal fillets.
Closterium curtum, Brebisson, in Menegh. Synop. Destnid. in Linncea 1840,
p. 237. Kutzing, Phycologia Germanica, p. 132. Penium curtum, Brebisson, in lit. cum icone (1846).
Near Bristol, Mr. Thwaites. Penzance, /. R.
Falaise, Brebisson. Germany, Kutzing.
110 BRITISH DESMIDIEiE.
Frond miuute, smooth, two to three times longer than broad, slightly con- stricted at the middle, attenuated and rounded at the ends. Endochrome in three or four longitudinal fillets, which are interrupted at the suture. End \iew circular, its endochrome with four geminate rays.
This plant was placed in Penium by M. De Brebisson because its endochrome is arranged in fillets, but in every other respect it agrees better with some of the preceding species of this genus. It is more obtuse than the usual form of Costnarium attenuatum, but I have occasionally seen specimens of the latter so nearly resembling the figure of C. curtum that I have doubted to which species they belonged. It is much smaller than C. turgidum, and tapers more than C. Cucurbita and C.'Thioaitesii.
Length of frond -^ of an inch ; greatest breadth yoVz-
Tab. XXXII. fig. 9. a. mature frond ; b. empty frond ; c. end view of frond with stellate endochrome.
32. C. attenuatum (Breb.) ; frond fusiform, three or four times longer than broad, slightly constricted at the middle ; transverse view circular.
Costnarium attenuatum, Brebisson, in tit. cum ieone (1846). Near Bristol, Mr. Thwaites. Swansea, J. R. Falaise, Brebisson.
Frond three or four times longer than broad, tapering, its ends obtuse ; end view circular. The empty frond is finely punctate.
Costnarium attenuatutn is much smaller and more tapering than C. tiir- yidutn, and has less-rounded ends. Its fusiform frond distinguishes it from C. Thwaitesii and C. Cucurbita. In general it tapers more than C, curtum, but sometimes its ends are more obtuse, and then these species can only be distinguished by the different arrangement of their endochromes.
It is doubtful whether this plant and Costtiariiuti turgidum ought not to be removed to Peniutn.
Length of frond from ^^ to -j^ of an inch ; greatest breadth from yoVs to YW22 » breadth at constriction from y-^j^ ^*^ 10^9 9-
Tab. XVII. a, b. fronds in usual state ; c. empty frond ; d. transverse \-iew.
33. C. turgidum (Breb.) ; frond oblong, punctate, constricted at the middle and rounded at the ends ; transverse view circular.
Costiiariutn turgidutn, Brebisson, in lit. cutn icone (1846). Henfield, Mr. Jetmer. Swansea, /. R. Falaise, Brdbisson.
Frond large, oblong, turgid, about three times as long as broad, distinctly constricted at the middle and broadly rounded at the ends. Empty frond with numerous, muiute, scattered puncta.
Costnarium turgiduvi differs from the allied species in its much greater size. It is comparatively longer and more tapering than C. Cucurbita and C. Thwaitesii, and its ends are more rounded than those of C. attenuatutn.
BRITISH DESMIDIE^. Ill
Length of frond y-iir o^ '"^^ i"t>li ; greatest breadth 2^ ; breadth at con- striction ^j4y
Tab. XXXII. fig. 8. a. mature frond ; b. empty frond ; c. transverse view.
9. XANTHIDIUM, Ehr.
Frond simple, constricted in the middle ; segments compressed, entire, spinous, having a circular projection near the centre, which is usually tuberculated.
In this genus the frond is simple; and deeply constricted at the middle ; its segments are slightly compressed, turgid, entire, either reniforra, orbicular or angular 5 they are furnished with spines, which, simple or branched, are either scattered or confined to the margin ; in the latter case they are arranged in two rows, one on each side of the marginal line. Near the centre of each segment is a remarkable circular projection on both surfaces. These projections are usually surrounded by a beaded circle of pearly granules or tubercles, which are most evident in a lateral or transverse view.
Xanthidium requires to be distinguished from three genera, viz. Siaurastrum, Arthrodesmus, and Cosmarium. Its resemblance to Stau- rastrum is more apparent than real, and will probably mislead no one "who has examined a plant belonging to that genus, in which the cells are angular irrespective of the processes. In Arthrodesmus each seg- ment has only two spines, one on each side, and there are no central projections.
The connection with Cosmarium is far more intimate ; in fact the sole distinctive character that can be relied upon is the presence of spines in this genus. Meneghini indeed still further reduces the number and value of the differential marks, by retaining in Xanthi- dium merely those species whose spines are scattered over the surface, whilst he refers to Cosmarium those in which the spines are confined to the margin. I think however that his views cannot be admitted, and that we must either retain the genus as formed by Ehrenberg, or unite all the species with Cosmarium; for in X. armatum the principal spines are marginal, and many specimens, especially in a young state, have none other.
I have followed preceding writers in taking the specific characters chiefly from the form and position of the spines ; but Mr. Jenner con-
112 BRITISH DESMIDIEjE.
siders that the central protuberances will afford better distinctive marks of some species. However, I have seen too few examples to decide this question.
One plant {X. octocorne, Ehr.) without central projections, and in other respects different from the true species of Xanthidium, I have re- tained here, because I am unable to assign it a more proper situation.
* Spines divided at the apex.
1. X. armatum (Breb.); segments broadest at the base; spines short, stout, terminated by three or more diverging points.
Cosmarium armatum, Brebisson, Menegh. Synop. Desmid. in LinncBa 1840,
p. 218. Xanthidium furcatum, Ralfs, in Annals of Nat. Hist. v. 14. p. 466. t. 12.
f. 1 (1844), excluding synon. ; Trans, of Bot. Soc. of Edinburgh, v. 2.
p. 154. t. 17. Jemier, Ft. of Tmiliridge Wells, p. 194. Hassall, Brit.
Alg. p. 359. Euastrum armatum, Kiitzing, P%. Germ. p. 137 (1845). Xanthidium armatum, Brebisson, in lit. (1846),
Common. North Wales ; near Carmarthen ; and Penzance, J. R. Sussex ; Kent ; Weston Bogs near Southampton, and New Forest, Mr. Jenner. Herts, Mr. Hassall. Kerry, Mr. Andrews. Ireland, Mr. Moore. Aberdeenshire, Mr. P. Grant and Dr. Dickie. Banffshire, Mr. P. Grant. Ambleside, West- moreland, Mr. Sidebotham.
Falaise, Brebisson. Germany, Kiitzing.
This species forms, at the bottom of shallow pools, cloud-like masses, which being detached, immediately rise to the surface. Its fronds, dispersed like minute glittering dots through the connecting cloud-like substance, are visible to the naked eye.
Frond comparatively large, deeply constricted, the constriction forming a linear notch on each side ; segments nearly equal in length and breadth, broadest at the base, their ends rounded or truncate ; spines short, stout, divided at the apex ; of these there are generally six pairs, which are marginal, and situated three on each side ; a few others usually are scattered on the disc.
The central protuberances are cylindrical, truncate, and bordered by pearly granules which produce a dentate appearance, especially in the end and lateral views. The empty frond is minutely punctate. The end \'iew is elliptic.
I have gathered a single sporangium of Xanthidium armatum at Dolgelley ; it was large and orbicular, with depressed tubercles. Having seen but this example, I am unable to say whether these tubercles eventually elongate into spines.
Xanthidium Artiscon, Ehr., differs from this species not only in its smaller size and its differently-shaped segments, but also in its longer spines, which are nearer the ends than those of X. armatum.
Length of frond yig- of an inch ; breadth -^-^ ; thickness -^ ; breadth at constriction -A^.
BRITISH DESMIDIEyE. 113
Tab. XVIII. a. frond with endochrome ; b. side view ; c, d. fronds acquiring new segments by division ; e. empty frond ; /. transverse view ; y. sporangium with empty segments of the conjugated fronds.
** Sinnes subulate.
2. X. aculeatum (Ehr.) ; spines subulate, more or less scattered ; cen- tral projections truncate, obscurely dentate.
Xanthidium aculeatum, Ehr. Abh. d. Berl. Ak. (1833), p. 318 ; Infus. p. 147. t. 10. f. 23. Meneghini, Synop. Desmid. in Lmncea 1840, p. 224. Ralfs, in Annah of Nat. Hist. v. 14. p. 467. t. 12. f. 2 ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 1 55. t. 1/. Jenner, Fl. ofTunbridge Wells, p. 194. Hassall, Brit. Alg. p. 360.
Weston Bogs near Southampton ; Ashdovra Forest, and Tunbridge Wells, Mr. Jenner. Penzance, J. R. Yate near Bristol, Mr. Thwaites.
Germany, Ehrenberg.
Frond deeply constricted at the middle, so as to form a Hnear notch on each side ; segments somewhat reniform, tvdce as broad as long ; spines subulate, short, marginal and scattered. The central projections, as seen in end or lateral views, are cylindrical, truncate, and bordered by pearly granules which give a dentate appearance, but less conspicuously than in Xanthidium armatum.
Xanthidium aculeatum varies in the arrangement and number of its spines. The Bristol specimens have a far larger central projection than the other speci- mens which I have seen.
This species is distinguished from all the following by having its spines more or less scattered.
Length of frond, not including spines, from g-i^ to -g-fy of an inch ; including spines, from g^-j to 3-^-3 ; breadth, not including spines, from 3-i^ to 3^^ ; in- cluding spines, from -^^ to -^-^ ; breadth at constriction from y-g^g ^^ ttVt-
Tab. XIX. fig. 1 . a,e, g. fronds with endochrome ; b, empty frond \ c,h. side views; </,_/. end ^'iews.
3. X. Brehissonii ; spines subulate, marginal, geminate; central
projection somewhat truncate and margined with pearly granules.
/3. varians ; segments broader and more irregular ; spines some- what irregular and unequal.
Binatella actdeata, Brebisson, Alg. Fal. p. 58. t. 8 (1835).
Cosmarium aculeatum, Meneghini, Synop. Desmid. in Einncea 1840, p. 218
(ui part). Euastrum, No. 1 1, Bailey, Amer. Bacil. in Amer. Journ. of Science and Arts,
V. 41. t. l.f. 13 (1841). Xanthidium bisenarium, Ehrenberg, Verb, und Einfluss des mikrosk. Lebens
in Sad- %md Nor d- Amer. (1843). Xanthidium aculeatum, Brebisson, in lit. cum icone (1846).
a. Piltdown Common, Mr. Jenner. Bristol, Mr. Thwaites. Penzance, J. R. l3. Piltdown Common, Sussex, 3Ir. Jenner. Trewellard near Penzance, J. R.
Falaise, Brebisson. West Point, New York, Bailey.
114 BRITISH DESMIDIE^.
Frond deeply constricted at the middle ; segments broader than long ; spines marginal. In a. all the spines are geminate and equal, but in /3. they are more or less unequal and not so regularly geminate, and occasionally also a few are scattered. Mr. Jenner finds, both in the Sussex and the Cornish specimens of this variety, a single spine interposed between the two central pairs and the lateral ones. This I have also observed, but not invariably. The central pro- jections resemble those of Xanthidium aculeatum, but the pearly granules are smaller. I believe that every species of Xanthidium except X. 1 octocorne is punctated, but the puncta can be detected only by the highest powers of the microscope.
By Brebisson this species is considered the X. aculeatum, Ehr., but Ehren- berg's description and figure represent the spines as scattered. According to Professor Bailey's figure in his * American Bacillaria,' this plant is probably the Xanthidium bisenaritcm, Ehr., but that name is mapplicable to our forms. The number of spines seems to be variable. Bailey's and Ehrenberg's figures have six pairs of spines, Brebisson' s eight, whilst in the Sussex specimens there are generally ten, to each segment.
Length of frond, not including spines, ^-fr ^^ ^^ ^^^^^ ' mcluding spines, -^^ ; breadth, not includmg spines, ^^^ ; including spines, -g^ ; breadth at con- striction -j-aVo-
Length of var. /3, not including spines, j^ ; including spines, -^^ ; breadth, not including spines, -^ ; including spines, ^-^ ; breadth at constriction yaVs •
Tab. XIX. fig. 2. a. front view of typal form ; b. dividing frond of var. (3 ; c. empty frond ; d. end view.
4. X.fasciculatum (Ehr.) ; segments with 4-6 pairs of subulate, mar- ginal spines ; central projections minute, conical, not beaded, a. Each segment with four pairs of spines.
Xanthidium fasciculatum, Ehr. Infus. p. 146. t. 10. f. 24. a. (1838). Ralfs, in Annals of Nat. Hist, v. 14. p. 467. t. 12. f. 3. a, h, c, d ; Trans, of Bat. Soc. of Edinburgh, v. 2. p. 154. t. 17. Jenner, Fl. of Tunbridge Wells, p. 194.
Cosmarium antilopceum, Brebisson, in Menegh. Synop. Desmid. in Linncea 1840, p. 218.
JEuastrum, No. 10, Bailey, Amer. Bacil. in Amer. Journ. of Science and Arts, V. 41. p. 296. t. 1. f. 10 (1841).
Euastrum fasciculatum, Kiitzing, Phy. Germ. p. 137 (1845).
Xanthidium polygonum, Hassall, Brit. Freshwater Alg. p. 360, excluding synonyms (1845).
Xanthidium fasciculatum,var. antilopceum, Brebisson, in lit. cum icone (1846).
/3. polygonum ; six pairs of spines to each segment.
Xanthidium fasciculatum /3. polygonum, Ehr. Infus. t. 10. f. 24. b. (1838).
Ralfs, in Annals of Nat. Hist. v. 14. t. 12. f. 3. e; Trans, of Bot. Soc.
of Edinburgh, v. 2. p. 154. Xanthidium fasciculatum, Hassall, Brit. Alg. p. 359 (1845).
a. Common. Dolgelley and Penzance, J. R. Sussex ; and near Southamp- ton, Mr. Jenner. Yate near Bristol, 3Ir. Broome. Kerry, Mr. Andrews,
nRlTISH DESMIDIE/E. 115
Aberdeenshire, Dy. D/c/v> aiulMr. P. Grant. Chesliire ; and Ambleside, West- moreland, Mr. Sidebof/iom. Rochdale, Mr. Cuatcs.
/3. Penzance and Dolgelley, J. R.
Germany, E/trenberff and K'utzing. Falaise, Brehisson. West Point, New York, Bailey.
Frond smaller than that of Xanthidium acideatum, deeply constricted at the middle ; segments twice as broad as long ; spines subidate, slender, ge- minate and marginal, in general slightly curved, but occasionally straight. Each segment commonly has only four pairs, though sometimes six. The central projections are conical, inconspicuous, to be detected only in end and lateral views, and even then liable to be overlooked. A mucous covering can usually be detected in a, but I am doubtful of its presence in /3.
The variety /3. Mr. Jenncr considers nearer to Xanthidium Brebissonii than to X. fasciculatum ; but, in my opinion, it agrees better with this species in size, and especially in the shape of the central projections.
Length of frond, not including spines, from -j\^ to -^^ of an inch ; including spines, from 3^ to ^^ ; breadth, not including spines, from -^\-^ to -^^ ; in- cluding spines, from -^^ to -^\-^ ; breadth at constriction y-gVs-
Length of var. /3, not including spines, j^t ; including spines, -^^ ; breadth, not including spines, -^^ ; including spines, 3^ ; breadth at constriction Y9V3 •
Tab. XX. fig. 1. a. front view of frond with endochrome ; b. front view of frond with mucous covering ; c. empty frond ; d. transverse view ; e. lateral view.
Tab. XIX. fig. 4. var. /3. a. front view of frond with endochi'ome ; b. empty frond ; c. lateral view ; d. end \'iew.
5. X. cristatum (Breb.) ; segments with a solitary spine on each side at the base, the other spines geminate.
a. Segments I'eniform ; spines scarcely curved. Xanthidium cristatum, Brebisson, in lit. (1846).
/3. uncinatum, Breb.; segments truncate at the end; spines uncinate.
Xanthidium uncinatum, Brebisson, mi /^7. cum icone (1846). Xanthidium cristatum /3. uncinatum, Brebisson, in lit. (1846).
a. Not uncommon. Dolgelley and Penzance, J.R. Ambleside, Mr. Side- botham. Aberdeen, Mr. P. Grant. Pulborough, Sussex, 3Ir. Jenner.
13. Ambleside, Westmoreland, Mr. Sidebotham. Dolgelley, /. E. a. and p. Falaise, Brebisson.
Frond smaller than that oi Xanthidium fascicidatum, the spines subulate and marginal ; each segment has four pairs, and on each side of the base a solitary one ; the central elevations, which are less distinctly granulate in a. than in /3, are scarcely -visible in a front view, but in an end one form slight, lateral, conical projections, the pearly granules encircling them like a necklace. In o. the segments are subreniform and all their spines nearly straight. The seg- ments in j3. are about equal in length and breadth, the ends being truncated,
I
116 BRITISH DESMIDIE^.
hence they are somewhat trapezoid ; their basal spines are nearly straight, the rest are curved.
This species is sufficiently marked by its solitary basal spines.
Length of frond, not including spines, -^^ of an inch ; including spines, gJ-g- ; breadth, not including spines, ^-Ir 5 including spines, -^^ ; breadth at constriction y^^-g-.
Length of frond of var. tcncinatnm, not including spines, -j^ ; including spines, -3^ ; greatest breadth, not including spines, ^iy ; including spines, -^^ ; breadth at end yaVo 5 hreadth at constriction -a^Vg.
Tab. XIX. fig. 3. a. front view of typal form ; b. empty frond ; c. end view ; d. front view of var. uncinatum ; e. empty frond ; f. end view.
6. X? octocorne (Ehr.) ; segments much compressed, without a cen- tral protuberance, trapezoid, each angle terminated by one or two spines.
a. One spine at each angle.
/8. major ; larger ; two or more spines at each angle. Arthrodesmus octocornis, Ehr. In/us. p. 152 (1838). Hassall, Brit. Alg.
p. 357. Brebisson, in lit. Micrasterias octoco?'nis, Meneghini, Si/nop. Des?nid. inLinncea 1840, p. 216. Cosmarium jpalmatum, Brebisson, according to Menegh. in Synop. Besmid.
(1840). Staurastrumi octocorne, Ralfs, in Annals of Nat. Hist. v. 15. p. 159. t. 12.
f. 3 (1845) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 145. t. 15. Xanthidium octocorne, Ehr. Meteorp. t. 1. f. 22. Euastriim octocorne, Kiitzing, Phy. Germ. p. 134 (1845).
a. Dolgelley and Penzance, /. R. Yate near Bristol, Mr. Broome. Amble- side, Westmoreland, Mr. Sidebotham. Pulborough, Sussex ; Reigate, Surrey ; and Weston Bogs near Southampton, Mr. Jenner. /3. Dolgelley, /. R.
a. Germany, Ehrenberg and Kiltzing. Falaise, Brebisson. Worden's Pond, Rhode Island, Bailey.
Frond minute, deeply constricted at the middle ; segments trapezoid, each angle terminated by one or more straight spines, the intervals between the angles concave.
The variety /3, which I have gathered mixed with the more common form, is usually larger, and its appearance, on account of the geminate spines, differs so much from a. that Mr. Jenner regards it as another species ; but I believe that no dependence can be placed on the number of spines as a specific distinction, for in specimens which I sent to Mr. Jenner, he discovered one frond whose lateral spines were single and end ones geminate, and other fronds with three spines on each angle of one segment and two on each angle of the other ; some again with the lateral spines geminate and the end spines in threes. I have, in one instance, seen the spines double on one segment and single on the other.
The proper position of this plant is so doubtful, that different observers have referred it to widely different genera. Ehrenberg placed it first in Ar- throdesmus and afterwards in Xanthidium : Brebisson considered it a Cos-
BRITISH DESMIDIK.K. 117
marium and more recently an Arfhrodesmus ; whilst Meneghini and Kiitzing unite it with the Micrasterice. It differs from the true species of Xanthidium, not only by usually having its spines in a single series, but also by its more compressed segments, and by the absence of a central projection ; for which reasons Mr. Jenner proposes to make it the type of a new genus, connecting as it were Xont/iidimn with Arthrodesmus or Staurastrum. Since there is so much diversity of opinion, I have thought it advisable to keep it in Xan- thidium until its proper situation can be determined with greater certainty.
Length of frond ^^^ of an inch ; greatest breadth y^Vs '■> breadth at con- striction 5^1^.
Length of frond of var. /3. yoVo of an inch ; greatest breadth -gi^ ; breadth at constriction -a-gVy
Tab. XX. fig. 2. a. front view of frond with endochrome ; b. empty frond ; c. end view ; d, e. fronds acquiring new segments by chvision ; f. front view of a frond of var. /3. with endochrome ; g. empty frond ; h. side \'iew ; ^. end view.
10. ARTHRODESMUS, Ehr.
Frond simple, compressed, constricted at the middle ; segments en- tire, with a single spine on each side.
The fronds are simple, much compressed and deeply constricted at the middle ; the segments, which are broader than long, have a single spine or mucro on each side, but are otherwise smooth and entire.
The sporangia of one species only have hitherto been observed ; they are spinous.
Where the plants should be placed, to the reception of which I have restricted this genus, has been left in much uncertainty. Ehren- berg, making no distinction betw^een constricted and binate cells, has associated them with others belonging to Scenedesmus to form his Arthrodesmus ; Meneghini assigns them to Staurastrum, and Kiitzing to Euastrum. In my papers in the 'Annals of Natural History,' I followed the arrangement of Meneghini, but at the same time sug- gested that these plants should be united with Arthrodesmus octo- cornis, Ehr., in a distinct genus, for which Ehrenberg's name might be retained. This suggestion Mr. Hassall has adopted in his ' British Freshwater Alga ' ; and it is approved by Brebisson. Mr. Jenner however considers that they belong to Staurastrum; and if he is correct in his supposition that he has met with one species some spe- cimens of which were compressed, whilst others had three angles in an end view, the former arrangement ought to be restored. It must further be allowed, that in the front view the resemblance to some species of Staurastrum is very close.
I 2
118 BRITISH DESMIDIE.E.
1. A. convergens (Ehr.) ; segments elliptic, each having its spines curved towards those of the other.
Arthrodesmus convergens, Ehr. Infus. p. 152. t. 10. f. 18 (1838). Hassall,
Brit. Algce, p. 357. Staurastrum convergens, Meneghini, Synop.Desmid. inLinncea 1840, p. 228.
Ralfs, in Annals of Nat. Hist. v. 15. p. 158. t. 12. f. 1 ; Trans, of Bot.
Soc. of Edinburgh, v. 2. p. 145. t. 15. Brebisson, in lit. Euastrum, No. 12, Bailey, in Amer. Joxirn. of Science and Arts, v. 41. p. 296.
t. 1. f. 11 (1841). Euastrum convergens, KUtzing, Phy. Germ. p. 136 (1845).
Dolgelley and Penzance, /. R. Sussex and Kent, Mr. Jenner. Herts, Mr. Hassall. Yate near Bristol, Mr. Broome. Aberdeenshire, Dr. Dickie and iifr. P. Grant. Kerry, Mr. Andreios. Near Congleton, Cheshire ; and Ambleside, Westmoreland, 3Ir. Sidebotham. Rochdale, 3Ir. Coates.
Germany, Ehrenherg, K'dtzing. Falaise, Brebisson. West Point, New York, Bailey.
Frond smooth and deeply constricted at the middle ; the transversely elliptic segments have on each side a curved spine which converges with the similar one of the other segment.
The frond has a gelatinous covering, which is sometimes distinctly seen, sometimes imperceptible.
Arthrodesmus convergens differs from A. Incus by its larger size and elliptic segments.
Length of frond from ^-i-g to -g^ of an inch ; breadth, not including spines,
from g-L- to j^y ; including spines, from 3J j to 3-!^ ; breadth at constriction 1
2 36 8*
Tab. XX. fig. 3. a. frond with endochrome ; b. empty frond ; c. end view ; d. frond dividing.
2. A. Incus (Breb.) ; segments with end margin truncate.
a. Segments externally lunate ; spines diverging. /8. Segments gibbous on each side near the base ; spines of the one segment parallel to or converging with those of the other.
Cosmarium Incus, Brebisson (1839), according to Meneghini in Synop.
Desmid. Staurastrum Incus, Meneghini, Synojo. Desmid. in Linncea 1840, p. 228.
Ralfs, in Annals of Nat. Hist. v. 15. p. 158. t. 12. f. 2 ; Trans, of Bot.
Soc. of Edinburgh, v. 2. p. 145. t. 15. Euastrvm, Bailey, iti Amer. Jotirn. of Science and Arts, v. 41. t. 1. f. 12?
(1841). Euastrum retusum, KUtzing, Phy. Germ. p. 136 (1845), (according to
KUtzing in lit. cum icone). Arthrodesmus Incus, Hassall, Brit. Freshwater Algce, p. 357 (1845).
Dolgelley and Penzance, J. R. Weston Bogs near Southampton ; and several stations in Sussex, Mr. Jenner. Yate near Bristol, Mr. Broome. Aberdeenshire, Mr. P. Grant and Dr. Dickie. Near Ambleside, Westmore- land, Mr. Sidebothatn.
Falaise, Brebisson. Germany, Kiitcing. West Point, New York, Bailey.
BRITISH DESMIDIE.E. 119
Frond smooth, minute, deeply constricted at the middle. The fronds are truncated at the ends and have a mucro at each angle ; a distinct neck at the constriction is sometimes present, sometimes wanting. In o. the segments are semilunate and the spines usualW directed outwards. The variety p. is generally larger than a ; its segments are nearly equal in length and breadth, and being rather suddenly rounded off at the constriction, present a gibbous- like appearance on each side ; the spines in j3. are stouter, and those of one segment slightly converge with those of the other. This form is considered a distinct species by Mr. Jcnner, who thinks that its end view is sometimes triangular, and that it unites Arthrodesmvs with Stanrastnim.
The orbicular sporangia have been gathered in Sussex by Mr. Jenner, and I have met with them at Dolgelley and Penzance ; they have subulate spines like those of Staurastrum dejectum, which they resemble, except in their smaller size.
This species is variable both in the form of its segments and in the direction of its spines ; the ends however are always truncate ; a character which affords a good distinction between it and A. convergens.
Euastnim Incus o^ Kiitzing's 'Phycologia Germanica' {Arthrodesmus tni- nutus, Breb. MS.) appears, from a drawing which he sent me, to differ merely in the smaller size and in its parallel spines. I fear it is scarcely distinct.
Arthrodesmus Incus, m the front view, has nivich the appearance of some states of Staurastrum dejectum ; it is nevertheless usually smaller, and its ends are more decidedly truncate.
Length of frond (Tab. XX. fig. 4. a.) y^Va ^^ ^" inch; breadth yoVo 5 length of frond (fig. 4. e.) from y^Vs" ^^ \ s'e i > breadth, not including spines, from Y^ts to -iXTo 5 ii^cluding spines, from -^\^ to j^ ; breadth at con- striction from gg^^g to a-gVr 5 diameter of sporangium, vnthout spines, y4\o > including spines, -y-^-j.
Length of frond of var. /3. -§4-3' breadth, not including spines, yy-i^; including spines, -g^ ; breadth at constriction -YTTf
Tab. XX. fig. 4. a, e. fronds with endochrome ; b. empty frond ; c, h. end views ; d. frond dividing ; i. fronds conjugating ; k, I. sporangia ; /. frond of var. /3. vidth endochrome ; g. empty frond.
11. STAURASTRUM, Me?/m.
Frond simple, constricted at the middle ; end view angular, or cir- cular with a lobato -radiate margin, or, rarely, compressed with a process at each extremity.
Frond mostly minute, simple, more or less constricted at the middle, and thus forming two segments, which are often somewhat twisted, generally broader than long, and in many species elongated laterally into a process, so that the constriction on each side is a roundish or angular sinus ; in other respects the front view shows the segments quite entire.
120 BRITISH DESMIDIE^.
The end vievv varies in form : in most of the species it is trian- gular or quadrangular, and the angles are either rounded or elongated into rays ; in some it is circular with five or more processes forming marginal rays ; in a few species it is compressed and the extremities terminate by a process.
Ehrenberg in his great work has distributed the plants, which I shall here describe, among different genera according to the number of angles or processes seen in an end view. Thus he refers those with three angles to Desmidium, and those with four to Staurastrum, and he formed his genus Pentasterias for the reception of a plant with five rays. But this arrangement appears unnatural; not only be- cause it separates nearly allied forms, but also because the number of rays, as Meneghini remarks, is not constant even in the same species : Professor Bailey says, when describing an American spe- cies, "The number of arms is usuall}' three, but I have met with specimens in which one corpuscule had three and the other four arms, others in which both had four, and others again in which both had five arms." I have myself seen fronds of Staurastrum paradoxum and S. dejectuni, one segment of which had four, and the other only three rays. I have generally found the Pentasterias margaritaceum of Ehrenberg with six rays, although not uafrequently with five, and occasionally with seven rays to each segment. Since we already know that about half the British species vary in the number of their rays, and specimens with three rays conjugate with four-rayed ones, the number of rays is not only altogether useless as a generic character, but it does not distinguish species and scarcely indeed varieties.
Staurastrum contains more species than any other genus in the family. M. de Brebisson enumerates forty in a list which he has sent me, to which several must be added that have been figured by Professor Bailey and others. The species exhibit a great variety of forms, and but little affinity can be traced between many of them : — as, for instance, between Staurastrum tumidum and ^. paradoxum, or between S. dejectum and S. bacillare. Nevertheless, desirable as it would be to separate plants so little allied, it seems better to keep them together for the present than prematurely to attempt their separation.
I should greatly have preferred Kiitzing's name Phycastrum to Staurastrum ; for the latter is applicable only to a limited number of the species. Still, as it had been previously employed by Meneghini
BRITISH DESMIDIE^. 121
and Brebisson, the rule established in such cases scarcely permits its exchange for the more appropriate term.
Sporangia of several species have been gathered. They are gene- rally spinous, but diifer in other respects.
A little care will distinguish Staurastrum from the other genera in this family, although some of its species appear at first sight to ap- proach forms which belong to them. It differs from Desmidium in never forming a filament ; and from Arthrodesmus and Cosmarium by its angular shape, or by having the ends elongated into processes. Some species bear a considerable resemblance to species of Xan- thidium, to which genus Ehrenberg refers them ; but in Xanthidium the frond, irrespective of the spines, is not angular in the end view, and there is a projection at the centre of each segment in the front view.
* Frond smooth, or rough with minute puncta-like granules ; end view with the lobes or angles inflated and mucronate or awned. t Frond smooth. ]. S. dejectum (Breb.) ; segments smooth, lunate or elliptic; con- stricted portion very short ; end view with inflated awned lobes. a. Segments externally lunate, awns directed outwards.
Sfaurasfrum dejectum, Breb., Meneghini, Si/nop. Desmid. in Linneea 1840,
p. 227. Brebissou, in lit. cum icone. Staurastrum mucronatum /S, Ralfs, in Annals of Nat. Hist. v. 15. p. 152
(1845). t. 10. f. 5.
/8. Segments elliptic, awns parallel. 7. Awns converging.
Staiirastrum mucronatum a. and y, Ralfs, in Annals of Nat. Hist. v. 15.
p. 152. t. 10. f. 5 ; Trans, of Bot. Soc. of Edinljurgh, v. 2. p. 139. t. 13.
Jenner, Ft. of Tunbridge Wells, p. 192. Goniocystis (Trigonocystis) nmcronata, Hass. Brit. Alg. p. 350 (1845).
Common. Dolgelley and Penzance, /. R. Weston Bogs near Sonth- ampton ; Sussex ; Surrey ; and Kent, Mr. Jenner. Kerry, Mr. Andrews. Yate near Bristol, Mr. Broome. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Ambleside, Mr. Sidehotham. Rochdale, Mr. Coates.
Falaise, Brebisson. West Point, New York, Bailey.
Frond smooth, deeply constricted at the middle ; segments broader than long, Imiate or elliptic, awned, the awns subulate, varying in length and di- rection. The end view shows three or four mammillate lobes or rays, each terminated by a hair-like mucro or awn.
Sporangia of this plant are more commonly met with than those of any other species in the family except Hyalotheca dissiliens. Since I first de- tected them at Dolgelley, I have gathered them more or less abundantly every year, both at Dolgelley and at Penzance ; they have also been sent me by Mr. Jenner, Mr. Broome, Dr. Dickie and Mr. Thwaites.
122 BRITISH DESMIDIEiE.
The conjugated fronds are connected by the formation of a bag-hke recep- tacle or cell, which is colourless and very thin, and therefore difficult of detection. As this enlarges the fronds become more remote from each other, their segments partially separate at the constriction on the inner side, and the endochromes of both pass out and unite to form an orbicular body between them. In this state it resembles the sporangium formed by some species of Closterium. At first it is inclosed in an orbicular membrane much larger than itself; but as it increases in density, fine hairs make their appearance on the surface and gradually become stout spines ; the membrane then dis- appears, and the sporangium acquires its perfect state covered Avith conspicuous awl-shaped spines. At this stage the empty fronds seem scarcely connected with the sporangium, except that they lie on opposite sides of it, have their . openings towards it, accompany its movements, and always retain the same relative position.
The above description of the process applies, with occasional and slight variations, to the conjugation of the greater number of species in the Des- midiese whose sporangia have been noticed ; and I have detailed it at length in this place, not only because this species has afforded more numerous opportmiities for tracing the formation of its sporangium, but because it was the first example I had witnessed of the spinous kind, and I devoted more time to its examination than to any other.
Either more than one species has been included under this name, or the sporangia vary much in regard to their spines, which in the Penzance spe- cimens are fewer and appear at first like minute tubercles.
Staurastrum dejectum and a few other species form a distinct group, di- stmguished by their smooth fronds, the peculiar inflated or mammillate form of their angles, or rather lobes, in the end view, and by their terminal awn- like spines. In some respects they have more resemblance to the two plants placed in Arthrodesmus than to the other species of this genus. Should any change be required, I would rather remove them to Arthrodesmus than unite that genus with Staurastrum.
Staurastrum dejectum is larger than S. cuspidatum, its spines are shorter, and its segments are connected either without a band or by a very short one.
Length of frond -^\^ of an inch ; breadth yiy ; breadth at constriction jtst '■> length of awn ^g st '■> diameter of sporangium yi^ ; length of spine of spo- rangium from 2-Jo^ to YaVo-
Tab. XX. fig. 5. a, b, c. front \dews of frond ; d, e. end views ; /, y. con- jugated fronds ; li, i, k, J, m. different states of sporangia.
2. S. cuspidatum (Breb.) ; segments smooth, fusiform, connected by a long narrow band ; awns parallel or converging, but straight ; end view with inflated awned lobes.
Binatella tricusjridafa, Brebisson, Ale/. Fal. p. 57. t. 8 (1835). Staurastrum cuspidatum, Breb., Meneghini, Si/nop. Desmid. in Linufea 1840,
p. 226. Brebisson, in fit. cum icone. Phycastrum cuspidatum, Kutzing, Phj. Germ. p. 138 (1845).
BUITISII DESMIDJE.E. 123
Dolgelley and Penzance, J. R. Rochdale, Mr. Coates. Weston Bogs near Sontham})ton, 3Ir. Jenner.
Falaise, Brebisson. Germany, Kiitzing.
Frond usually smaller than that of Staurastrum dejectum ; segments smooth, fusiform or trimcate on the outer side, separated by a long band-like neck which is present also in the dividing frond between the old and new seg- ments; the subulate a'niis are elongated and straight, and either parallel to those of the other segment or convergent with them. The end view has three or four mammillate and awned lobes.
Staurastru7n cnsjndatum may be known from S. dejectum by the elongated band which connects the segments.
The sporangium of this species resembles that of S. dejectum, but has fewer spines.
Length of frond ^-i-3 of an inch ; breadth yoVo 5 breadth at constriction 3 3^3^ ; diameter of sporangium g-^^.
Tab. XXI. fig. 1. a, b. fronds with endochrome ; e. frond dividing ; d. trans- verse Adew ; e. end >iew.
Tab. XXXIII. fig. 10. sporangium.
3. S. aristiferum ; segments smooth, the lobes in front view
prolonged into mammillate awned projections which are somewhat constricted at the base ; end view with three or four awned lobes.
Dolgelley, J. R.
Frond smooth, about as large as that of Staurastrum cuspidatum ; segments not separated by a band ; ends usually truncate, but the angles are elongated into mammillate processes, each terminated by a long avm ; end view as in the two preceding species.
Staurastrum aristiferum may be a variety of S. cuspidatum, bvit as it has no isthmus between the segments, and the angles in the front view are elon- gated, I have described it as distinct.
Length of frond -^ of an inch ; breadth yoVar 5 length of spine yvts 5 breadth at constriction -^q-^.
Tab. XXI. fig. 2. a. front view; b. end view.
4. S, Dickiei ; segments smooth, subelliptic, turgid ; spines
short, curved toward those of the other segment ; end view with three shghtly inflated mucronate lobes.
Aberdeenshire, Dr. Dic/cie. Dolgelley, /. R.
Frond smooth, larger than that of Staurastrum dejectum, deeply constricted at the middle ; segments tAvice as broad as long, elliptic, but having the outer margin more convex than the inner one ; spines short, curved and converging with those of the other segment. End view with three slightly inflated lobes, which are rounded and mucronate.
This plant was first sent me by Dr. Dickie, who pointed out its resemblance in a front view to Arthrodesmus convergens. It is however smaller, although
124 BRITISH DESMIDIE^.
it has an additional angle, and I have not detected any mucous covering. From the three preceding species it differs in its more turgid segments and in the short, curved, converging spines. As the sides are but slightly concave, the end view is less decidedly lobed, the angles also are more rounded and less conspicuously mammillate. Staurastrum Dickiei is more like the S. brevi- sjpina, Breb., but that species has larger segments, which are semiorbicular and very turgid, and its spines are very minute, and detected, at least in the dried specimen, with difficulty. The Scotch specimens have their spines smaller than those of the Welsh ones, and therefore approach still more closely to S. brevispina.
Length of frond -g-iy of an inch ; breadth gig ; length of awn -^^^z '■> breadth at constriction ^ g^^ ^ .
Tab. XXI. fig. 3. a. front view ; b. end view.
5. S. brevispina (Breb.) ; segments smooth, turgid, elliptic, minutely mucronate ; end view three-lobed, each lobe terminated by a short mucro.
Staurastrum brevispina, Brebisson, Meneghini, Synop. Desmid. in Linncea 1840, p. 229. Brebisson, in lit. cum icone et specimine.
Henfield, and near Pulborough, Sussex, Mr. Jenner. Penzance, J. R.
Falaise, Brebisson.
Frond larger than that of Staurastrum dejectum ; segments elliptic or reniform, very turgid, twice as broad as long, having on each side a very minute spine or mucro which is often difficult to detect. A drawing sent me by M. de Brebisson represents the spines subulate and converging with those of the other segment. In Mr. Jenner's specimens there is a minute papilla rather than mucro at each lobe, and in the front view these papillae are situ- ated more outwardly than the spines are in M. de Brebisson' s specimens. The end view is three-lobed; the lobes are inflated and have broadly roimded ends.
Length of frond -^^ of an inch ; breadth g-j-Q ; breadth at constriction WJT ; length of spine T^igy.
Tab. XXXIV. fig. 7. a. front view ; b. end view ; c, d. front and end views from drawings by M. de Brebisson.
tt Frond rough with minute granules.
6. S. lunatum ; frond rough with puncta-like granules ; seg- ments externally lunate, with an awn at each angle ; end view with three inflated awned lobes.
Penzance, /. R.
This species resembles in figure Staurastrum dejectum, but it is larger. Frond deeply constricted at the middle ; segments semilunate, the convex margins united, the outer margin rough with minute granules and truncate, each angle tipped by an awn or mucro which is directed obliquely outwards. End view three-lobed, the lobes inflated, obtuse and awned.
Its rough frond distinguishes Staurastrum lunatum from all the preceding species, and the inflated awned lobes of its end-^dew from all the following ones.
BRITISH DESMIDIE.E. 125
Length of frond -^^ of an inch ; breadth -^ ; breadth at constriction 2T37 ; length of spme ^oW- Tab. XXXIV. fig. 12. a. front view ; b. end view.
** Frond smooth ; angles in end view broadly rounded.
7. S. mnticum (Breb.) ; segments smooth, elliptic, end view showing
slightly concave sides and 3 — 5 rounded angles.
Binatella muticuyn, Brebisson, Alg. Fal. p. 57. t. 8 (1835). Staurastrum triloJmm, Meneghini, Conspect. Alg. Eug. p. 18 (1837). Staurastnun muticum, Breb. inMenegh. Synop. Desmid. in Linncea 1840 ; in lit. cum icone.
Dolgelley and Penzance, J. R. Ambleside, Mr. Sidebotham.
Falaise, Brebisson. Italy, Meneghini.
The frond, generally smaller than that of Staurastrum orbicidare, is quite smooth and has a mucous covering, wliich is sometimes distinct, but often it can only be ascertained by the appearance of a clear border round the frond which prevents the contact of other substances ; segments elliptic. The end view shows three or four angles, sometimes five, according to Meneghini ; the sides are slightly concave and the angles broadly rounded.
Statirastrtim muticum differs from S. orbiculare by its elliptic segments and mucous covering.
Length of frond -^yj of an inch ; breadth -g-g-g- ; breadth at constriction
2 5 0 0*
Tab. XXI. fig. 4. a, b. front view; c. end view of three-rayed state; d. end view of four-rayed variety.
Tab. XXXIV. fig. 13. Sporangium, from a drawing by M. de Brebisson.
8. S. orbiculare (Ehr.) ; segments smooth, semiorbicular ; end view bluntly triangular.
Desmidium orbiculare, Ehr. Ahh. der Berl. Ak. 1832, p. 292 ; Infus. p. 141.
t. 10. f. 9. Staurastrum orbiculare, Ralfs, in Annals of Nat. Hist. v. 15. p. 152. t. 10.
f. 4. (1845) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 138. t. 13.
Jenner, Fl. of Tunbridge Wells, p. 96. Brebisson, in lit. cum icone. Phycastrum orbiculare, Kiitzing, Fhy. Germ. p. 137 (1845). Goniocystis {Trigonocystis) orbicularis, Hassall, Brit. Freshwater Algce,
p. 349 (1845).
Dolgelley and Penzance, /. R. Sussex ; Kent ; and Weston Bogs near Southampton, Mr. Jenner. Ben Muich Dhu (alt. 3480 feet), Aberdeenshire, Br. Dickie. Aberdeenshire and Banffshire, Mr. P. Grant. Ambleside, Westmoreland, Mr. Sidebotham.
Germany, Ehrenberg and Kiitzing. Falaise, Brebisson. West Point, New York, Bailey.
Frond smooth, deeply constricted at the middle ; the segments are gene-^ rally in close approximation for their entire breadth, hence the frond is sub- orbicular. The end view is triangular, with sides either straight or slightly concave and rounded angles.
126 BRITISH DESMIDIF.^.
Sfaurasfrum orhiculare may be recognized by its smooth frond, angles broadly rounded and destitute of processes, and its orbicular form in a front view.
Sporangia, gathered at Dolgelley and Penzance, are orbicular, with subulate spines. The conjugating fronds are smaller than those in the ordinary state.
Length of frond t-qVt °^ ^^ mch ; breadth y-poT 5 breadth at consti'iction ■g-^Vr ; cliameter of sporangium -^-^ ; length of spine ^ ^^3 g .
Tab. XXI. fig. 5. a, c, d, h. front vieAV ; b,f, i. end view; e. transverse view ; g. sporangium.
9. S, tumidum (Breb.) ; segments smooth, elliptic or suborbicular ; end view bluntly triangular, each angle terminated by a nipple-like projection.
Binatella tumida, Brebisson, Alg. Fal. p. GQ (1835).
Staurastruyn orhiculare, Meneghini, Synop. Destnid. in Linncea 1840, p. 225.
Staiirastrum tumidum, Brebisson, in lit. cum icone (1846).
Piltdown Common, Sussex, Mr. Jenner. Dolgelley and Penzance, /. R.
Falaise, Brebisson.
Frond large and distinctly visible to the naked eye, smooth, deeply con- stricted at the middle, having a distinct gelatinous covering, which is often marked with close radiating striee ; segments elliptic or suborbicular. The end view is triangular or quadrangular, the sides are convex, the angles rounded, and each terminated by a nipple-like process ; some of these pro- jections are visible in the front view. In both views the margin of the frond appears striated. The empty frond is minutely punctate.
Length of frond ^^^ of an inch ; breadth -^\-^ ; breadth at constriction j-g-Q .
Tab. XXI. fig. 6. a. front view; b. end view of triangular form ; c. end view of quadrangular variety magnified only 200 times ; d. transverse view.
*** Frond with simple spines, hairs, or {rarely) acute granules ; angles, in end view, broadly rounded and entire.
10. S.muricatum (Breb.) ; segments semiorbicular, rough with conic granules ; end view triangular, with convex sides and broadly rounded angles.
Binatella muricata, Brebisson, Alg. Fal. p. && (1835).
Desmidium apiculosum, Ehrenberg, In/us. p. 142 (1838). Pritchard, Infus.
p. 184. Staurastrum muricatum, Brebisson, Meneghini, Synop. Desmid. in Linncea
1840, p. 22G. Xanthidium deltoideum, Corda, Ohseri\ Microscojvques sur les Animalcides
de Carlsbad, p. 29. t. 5. f. 38, 39 (1840). Staurastrum muricatum /3, Ralfs, Annals of Nat. Hist. v. 15. p. 154. t. 11.
f. 1. ^, e. (1845) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 141. t. 14. Phycastrum apiculosum, Kiitzing, Phy. Germ. p. 137^ (1845).
BRITISH DESMIDIE^. 127
Gonioci/sfis {Trigonocystis) muricatu /3, Ilassall, Brit. Freshwater Alyce, p. 351 (18-45).
Sussex, Mr. Jenner. Dolgelley, J. R.
Falaise, Brebisson. Germany, Ehrenherg, Corda, Kiitzing.
Frond deeply constricted at the middle, nearly equal in length and breadth, rough with minute conic granules or spines. End view triangular, its sides convex and angles broadly rounded.
Stoitrastrum mnricatum is larger than S. hirsutnm, and not hirsute, but rough with stout short granules or spines ; in the end view also the sides are more convex.
Length of frond -j^-g of an inch ; breadth j^.
Tab. XXII. fig. 2. a. front view ; b. end view.
11. S. hirsiitum (Ehr.) ; segments semiorbicular, rough with nu- merous hair-like spines ; end view with three rounded angles and straight or slightly convex sides.
Xanthidium hirstitum, Ehrenberg, Abh. der Bei'l. Ak. 1833, p. 318 ; Infus. p. 147. t. 10. f. 22. Meneghini, Sijnop. Desmid. hiLinncea 1840, p. 224.
Binatella hispid a, Brebisson, Alg. Fal. p. 58. t. 8 (1835).
Xanthidium pilosum, Ehr. Bericht der Be?'l. Ak. 1836 (according to Mene- ghini) .
Stanrastnon mnricatum, Ralfs, Annals of Nat. Hist. v. 15. p. 154. t. 1 1 . f. 1 . a, b, c (1845) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 141. t. 14. Jeimer, FL of Tnnbridge Wells, p. 194,
Euastrum {Xanthidiuni) hirsutum, Kiitzing, Phycologia Gertnanica, p. 13/ (1845).
Goniocystis (Trigonocystis) miiricata, Hassall, Brit. Freshwater Alg ce, p. 351 (1845).
Staiirastrum hirsutum, Brebisson, in lit. cum icone (1846).
Dolgelley and Penzance, J. R. Sussex, 3Ir. Jenner. Ambleside, Mr. Sidebotham. Rochdale, Mr. Coates. Yate, Mr. B?-oome. Aberdeenshire, Mr. P. Grant.
Germany, Ehrenberg, Kiitzing. Falaise, Brebisson,
Frond variable in size, about equal in length and breadth, deeply constricted at the middle ; segments semiorbicular, hirsute rather than spinous ; hairs numerous, scattered. End view triangular ; the sides straight or slightly con- vex, and the angles broadly rounded.
I have gathered sporangia at Dolgelley and Penzance. They are orbicular, their spines short, and branched at the apex.
The hair-like spines are characteristic of this species.
Length of frond from -g^ to ^^ of an inch ; breadth from -g^ to -^o ; breadth at constriction -gaVo 5 diameter of sporangium from yi^ to -^-^ ; length of spine of sporangium ^ q\ ^ .
Tab. XXII. fig. 3. a. front view of frond with endochrome ; b. front Aaew of empty frond ; c. end view of frond with endochrome ; d. end view of empty frond ; e. transverse view ; f immature sporangium ; g, h. mature sporangia.
128 BRITISH DESMIDIE.E.
12. S. teliferum ; segments reniform, bristly; end view trian- gular, with concave sides and broadly-rounded bristly angles.
Dolgelley and Penzance, J. R. Ambleside, M)-. Sidebotham. Hadlow Down near Mayfield, and several other stations in Sussex, 3Ir. Jenner.
Frond about as large as that of Staurastrum hirsidum, deeply constricted at the middle ; segments twice as broad as long, somewhat reniform, and fur- nished with scattered spines. End view triangular ; the spines variable in number and confined to the angles.
Staurastrum teliferum diifers from (S*. hirsutum in its longer spines, which are also fewer, stouter, and in the end view confined to the angles. It is a larger plant than S. Hystrix ; its spines are more numerous, and the end mar- gins in the front view are convex.
Length of frond yiy of an inch ; breadth -^\^ ; breadth at constriction •j^'yy ; length of spine xoW '■> diameter of sporangium y-L ; length of spine of spo- rangium ^ijW-
Tab. XXII. fig. 4. a. front view ; b. end view.
Tab. XXXIV. fig. 14. Sporangium.
13. S. Hystrix ; segments subquadrate, spinous; end view with
three or four rounded angles, each furnished with a few subulate spines.
Dolgelley, /. R. Near Storrington, Sussex, Mr. Jenner.
Frond very minute, smaller than that of any other species with simple spines, deeply constricted at the middle ; segments spinous, somewhat quadrilateral, about twice as broad as long, the end margin nearly straight. The spines are subulate, few in number, and in the front view most of them are lateral. The end view is triangular or quadrangular, and has concave sides and rounded angles. Six or eight spines are scattered on each angle, the sides and disk being naked.
Its smaller size and differently shaped segments vdll distinguish this species from Staurastrum teliferum.
Length of frond from y^^y to y^Vo ^^ ^^ "^^^^ '■> breadth from yJ^T ^'^ -^\-i '■> breadth at constriction yy g-g- ; length of spine ^^^^.
Tab. XXII. fig. 5. a. front view of frond with endochrome ; h. front view of empty frond ; c. end \iew ; d. transverse view of four-rayed variety.
**** ^fi^ i^i^ijD of frond showing four or more toothed lobes, which are either truncate or rounded, but never elongated into rays.
14. S. quadrangulare (Breb.) ; frond smooth; segments quadrangular, with a few marginal spines or teeth ; end view quadrilateral, with truncate angles either emarginate or dentate.
Staurastrum quadrangulare, Brebisson, m lit. cum icone (1846). Ambleside, Mr. Sidebotham. Falaise, Brebisson.
BRITISH UESMIDIEiE. 129
Frond very minute, smooth, deeply constricted at the middle, the constric- tion forming a linear notch on each side ; segments quadrilateral, twice as broad as long, with one or two minute but stout teeth at each angle. End view quadrangular, the sides concave, the angles truncate, and in British specimens emarginate.
A drawing of Stavrastnon qiiadrangulare sent me by Brebisson represents a much larger form. Its angles, which in the end view are broader, have four teeth at their truncate ends and two minute teeth on their upper surface ; but I concur with Mr. Jenner in regarding the British plant as a small variety of this species.
Length of frond yyVr ^^ ^'^ "^^^^ 5 breadth -yywz '■> breadth at constriction
2193'
Tab. XXII. fig. 7. a. front view with endochrome ; b. empty frond ; e. end view.
Tab. XXXIV. fig. 11. a. front view from a drawing by M. de Brebisson ; b. end view.
15. S. sexcostatum (Breb.) ; segments in the front view with a toothed angle at each side ; end view circular, with five or six broad, short, toothed lobes.
Staurastrum sexcostatum, Brebisson, Meneghini, Synopsis Besmid. in Linnaa
1840, p. 228 ; Brebisson, in lit. cum icone. Staurastrum Jenneri, Ralfs, Annals of Natural History, v. 15. p. 158. t. 11.
f. 8 (1845) ; Transactions of Bot. Society of Edinburgh, v. 2. p. 144.
t. 14. Jenner, Fl. of Tunbridge Wells, p. 194. Goniocystis {Pentasterias) Jenneri, Hassall, Brit. Freshwater Algce, p. 356
(1845).
Very rare. Between Mayfield and Hadlow Down, Sussex, Mr. Jenner. Yate near Bristol, Mr. Thwaites. Dolgelley, J. R.
Falaise, Brebisson.
Frond large, rough with conic granules which give a dentate appearance to the outline ; segments about as broad as long, produced into a toothed angle on each side, where also a triangular sinus is formed between the angles. The end view is circular and elevated in the centre, and has five or six broad, short, toothed, marginal lobes. The transverse view has a large central opening surrovmded by a row of large granules.
I refer this plant to Brebisson' s Staurastrum sexcostatum, on his own autho- rity, but a dravdng sent by him of S. sexcostatum represents a smaller state.
Length of frond -^^ of an inch ; breadth from ^-L to wr > hreadth at con- striction y-gVy
Tab. XXIII. fig. 5. a. front view of Sussex specimen ; b, c. end views ; d. transverse \'iew ; e. front view of Dolgelley specimen.
130 BRITISH DESMIDIE.E.
***** Frond smooth ; end view acutely triangular, with two accessory subulate sjiines to each angle.
16. S. monticulosmn (Breb.) ; segments with a forked spine on each side, and at the end about four short, stout, acute projections ; end view acutely triangular, with a bifid appendage to each angle.
Staurastrum monticulosum, Brebisson, Menegh. Synop. Besmid. in Linncpa
1840, p. 226. Phycastrum monticulosum, Kiitzing, Phycoloyia Germanica, p. 138 (1845).
Penzance ; very rare, t7. jR.
Falaise, Brebisson.
Frond smooth, rather large, deeply constricted at the middle ; segments somewhat elliptic, with a projection on each side forked like the tail of a swallow. The end margin has generally four remarkable projections, which are stout, twice as long as broad, acute, and look not unlike a cluster of pyra- mids. The end view is triangular, the angles acute. At the base of each angle, on the upper surface, is a bifid projection, the aciite points of which appear on each side.
Staurastrum monticulosum is a remarkable species, difficult to describe, but easily recognized by its figure*.
Tab. XXXIV. fig. 9. a. front view of French specimen ; h. end view ; both from drawings by M. de Brebisson.
17. S. pu7igens (Breb.) ; frond smooth, each end with about six subu- late spines, directed outwards ; each angle in the end view tapering into a spine, which has two smaller ones at its base.
Euastrum, No. 14, Bailey, Amer. Journ. of Science and Arts, v. 41. p. 297.
t. l.f. 14? (1841). Staurastrum puny ens, Brebisson, in lit. cum icone (1846).
Penzance ; rare, J. R. Cross-in-Haud, Sussex, Mr. Jenner.
Falaise, BrSbisson. "West Point, New York, Bailey.
Frond smooth, deeply constricted at the middle ; segments externally lu- nate, and having on the outer margin about six subulate spines, the lateral ones being the most conspicuous. The end view has three angles which taper gradually into subulate spines ; its iipper surface has two smaller spines at the base of each angle, which diverge and become visible on opposite sides.
Staurastrum puny ens agrees with S. monticulosum in having two spines on the up])er surface of each angle ; but its spines are more slender, and in the front view are all simple and directed outwards.
Tab. XXXIV. fig. 10. a. front view; b, c. end views.
* " S. monticulosum, Breb., cellulis e dorso triangularibus, apicibus acutis- simis, suprapositione bifidis, prominentia bifido-divaricata breviore, quoque angulo superimposita, promiuentiis in centro confluentibus, a latere ellipticis utrinque bifidis, exterius dentatis." — Meneyhini.
BRITISH DESMIDIE.E. 131
***=>:** Frond smooth ; front vieiv with divergwg processes divided at
the apex.
18. 8. brachiatum ; frond smooth ; front view with thick diver- ging processes which are deeply bifid or trifid at the apex ; end view with three or four rays.
Staurastrnm bijidum, Ralfs, Annals of Nat. Hist. v. 15. p. lol. t. 10. f. 3 (1845) ; Trans, of Hot. Soc. of Fdlnborr/h, v. 2. p. 138. t. 13. (Not Desmidiiim bifdum, Ehr., or P/u/castrum bifdum, Kiitzing.)
Goniocystis {Staurastrum) bifdum, Hassall, Brit. Freshwater Alyce, p. 355 (1845).
Dolgelley and Penzance, J. R. Near Bristol, Mr. Broome. Ambleside, Mr. Sidebotham. Craigendurroch and Glen Lin, Aberdeenshire, Dr. Bichie. Aberdeen, Mr. P. Grant. Reigate, Mr. Jenner.
Frond minute, smooth, scarcely constricted at the middle, truncate at the ends ; segments with three or four elongated, straight, tapering processes, which are directed outwards, and consequently diverge from those of the other seg- ment. In the front view each segment usually exhibits oidy two processes, the others being hidden behind them. The processes are usually trifid at the extremity, though sometimes merely bifid, in which latter case their diverging points are forked like the tail of a swallow : the same bifid appearance may occur in certain positions, even when three points are present. The end view has three or four rays, hyaline, stout at their base, and gradually tapering. In this view, as the frond is generally twisted, the rays of the lower segment may be faintly seen between those of the nearer one.
Sporangia have been gathered by Mr. Broome at Yate near Bristol ; they are quadrate and spinous, and afPord the only known example of a quadrate sporangium bearing spines. The emptied segments are easily detached ; the spines are subulate and few.
Staurastrum brachiatum may always be distinguished from S. paradoxum and S. tetracerum by its smooth and divided processes.
Length of frond jyt\ ^^ ^^^ iwch ; breadth yyVr 5 length of process from tbVs *^ TiVs" ; length of sporangium from yqVo ^° tIt » length of spine from
1 to -t
2732 ''" 2048*
Tab. XXIII. fig. 9. a. front view of frond ; b, c. dividing fronds ; d. end \-iew of four-rayed variety ; e,f,g. sporangia.
19. /S. l(£ve ; frond smooth; segments with short processes
forked at the apex and directed outwards ; end view with three or four bipartite angles.
Pool near the outlet of Llyn Gwernan, Dolgelley, J. R.
Fronds very minute, smooth, deeply constricted at the middle, the constric- tion producing a wide triangular notch on each side. Segments externally lunate or somewhat cuneate, but in general the outer margin is slightly protu- berant at the middle. Each angle terminated by a pair of short, stout, hyaline
K
132 BRITISH DESMIDIE.E.
processes, which are shghtly forked at the apex and directed outwards ; but in the front view seldom more than three or four processes are seen at once. End view with three or four bipartite angles, their divisions divergent, subulate, generally appearing acute at the apex, but sometimes, especially if looked at obliquely, forked as in the front "^iew.
Staiirastnim Iceve, in the front ^dew, agrees with S. brachiatum in its smooth frond and forked divergent processes ; but the constriction at the middle is greater, the processes are shorter, and if an angle be towards the eye its ge- minate character will be detected without much difficulty. In the end view this species is unlike any other.
Length of frond ywo ^^ ^^ ^^^^ ' breadth -^^^j '■> breadth at constriction •2^^ ; length of process from ^^3-5- to 3^.
Tab. XXIII. fig. 10. «, 6, e. front views ; d. end view ; e. transverse view.
******* Frond rough with puncta-like granules. t End view with entire, rounded or truncate, angles or short rays. 20. S. alternans (Breb.) ; segments rough, narrow-oblong, and, from their twisted position, unequal in the front view; end view wdth the angles of one segment entire, and alternating with those of the other.
Staurastnim ^/•^co?•?^e, Ralfs, in Annals of Nat. Hist. v. 15. p. 141. t. 11. f. 2 (1845) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 141. t. 14. Jenner, Fl. of Tunbridge W^ells, p. 194. (Not of Meneghini according to Bre- bisson.)
Goniocystis {Trigonoeystis) hexaceros, Hassall, Brit. Freshwater Algoe, p. 352 (1845).
Staurastnim alternans, Brebisson, in lit cum icone (1846).
Dolgelley and Penzance, J. R. Barmouth, Rev. T. Salwey. Weston Bogs near Southampton ; and several stations in Sussex, Surrey and Kent, Mr. Jenner. Near Bristol, Mr. Thivaites. Glen Lin, Aberdeenshire (alt. 1300 feet). Dr. Dickie. Near Aberdeen, 3Ir. P. Grant. Ambleside, Mr. Side- botham.
Falaise, Brebisson. West Point, New York, Bailey.
Frond rough with minute pearly granules, which, except on the margin, appear like puncta ; segments two or three times longer than broad, oblong, twisted, so that in the front view one of them appears shorter on one side, in consequence of the blending together of two of the angles. The end view is triangulai', with concave sides and very obtuse entire angles. The angles of the lower segment are seen alternating with those of the upper.
I formerly described this plant as the Staurastnim tricorne, but that species in the front view is prolonged at the sides into short processes ; I am not certain that the two are distinct, but in doubtful points I think it right to defer to M. de Brebisson' s opinion.
Staurastrum alternans may be known from S. dilatatum and S. punctii- latiim by its unequal segments in the front view and alternating angles in the end one.
imiTISH DESMID1E.E. 133
I have gathered the sporangia at Penzance ; they are orhicular and fur- nished with spines forked at the apex.
Length of frond yoVt ^^ ^^^ "><^^i '> breadth yxVir 5 hrcadth at constriction i__
3 2 0 5*
Tab. XXI. fig. 7. a. front view; b. end view ; c. transverse view.
21. S. punctulatum (Breb.) ; segments rough with puncta-Hke gra- nules, elhptic, equal; end view with broadly rounded angles and slightly concave sides.
Staurastnan jnoictulatiun, Brebisson, in Hi cttm icone (1846). Sussex, Mr. Jenner. Dolgelley, J. R. Falaise, Brebisson.
Frond larger than that of Staurastrum alternans, rough with minute pearly granules which appear like puncta ; segments tveice as broad as long, elliptic ; end view triangular with very blunt angles.
Staurastrum punctulatum may be distinguished from S. alternans by its equal and more turgid segments in the front view, and in an end one by its less concave sides. S. ruc/ulosum agrees with it in size and partly in form, but in that species the pearly granules are larger and few er, and at the angles appear like little spines.
Length of froud ^-^ of an inch ; breadth ^-|t ' breadth at constriction ^^i o'
Tab. XXII. fig. 1. a. front view ; b. end view of empty frond ; c. dividing fronds.
22. S. dilatatum (Ehr.) ; segments rough, fusiform, equal ; end view Mith four short, broad, truncate and entire rays.
Staurastrum dilatatum, Ehr. Infus. p. 143. t. 10. f. 13 (1838). Menegh.
Synop.Besmid. in Linncea 1840, p. 156. Pritch. Infus. p. 184. Ralfs,
Annals of Nat. Hist. v. 15. p. 143. t. 11. f. 5 ; Trans, of Bot. Sac. of
Edinburgh, v. 2. p. 143. t. 14. Phycastrum dilatatum, Kiitzing, Phyc. Germ. p. 138 (1845). Goniocystis (Staurastrum) dilatatum, Hassall, Brit. Freshwater Alycs, p. 353
(1845).
Dolgelley and Penzance, J. R. Rusthall Common near Tuubridge Wells, and Rackham near Pulborough, Sussex, 3Ir. Jenner. Yate near Bristol, Mr. Broome. Ambleside, Mr. Sidebotham.
Germany, Ehrenberg, Kiitzing. Falaise, Brebisson. West Pomt, New York, Bailey.
Frond very minute, rough with puncta-hke pearly granules, deeply con- stricted at the middle, the sinuses rounded ; segments fusiform, two or three times broader than long, equal, obtuse at the sides, and not elongated into processes. In the end view, which is quadrangular, the sides are concave, and the angles form short, broad, truncate rays, on which the granules are arranged
k2
134 BRITISH DESMIDIE^.
in transverse lines. Meneghini describes the rays as varying in number from three to five.
Staurastnim diJatatum differs from S. alternans in not being twisted ; its rays also (in an end view) are more truncate.
Length of frond ytot ^^ ^^ ^^^^^ 5 breadth xrrr '■> breadth at constriction
1
TTsi'
Tab. XXI. fig. 8. a. front Aaew of frond ; b. end \'iew ; c. transverse view.
23. S. margariiaceum (Ehr.) ; segments rough tapering at the con- striction, and having short lateral processes ; end view with five or more short, narrow, obtuse rays.
Pentasterias margaritacea, Ehr. Infus. p. 144. t. 10. f. 15 (1838). Pritch.
Infus. p. 185. f. 104. Stmirastrum margaritaceum, Menegh. Synoji.Desmid. mLinncea 1840, p. 227.
Ralfs, Jyinals of Nat. Hist. v. 15, p. 157. t. 11. f. 7 ; Trans. ofBot. Soc.
of Edinburgh, v. 2. p. 144. t. 14. Phycastrum margaritaceum, Kiitzing, Phycologia Ger-m. p. 138 (1845). Goniocystis {Pentasterias) margaritacea, Hassall, Brit. Freshwater Algee,
p. 356 (1845).
Dolgelley, J. R. Ashdown Forest, Sussex, 3Ir. Jenner. Stoke-Hill near Wells, Mr. Thwaites. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Am- bleside, Mr. Sidebotham.
Germany, Ehrenberg. Falaise, Brebisson. West Point, New York, Bailey.
Frond rough with minute pearly granules ; in the front view the segments are convex at the ends and slightly attenuated at their junction, and on each side there is a short, linear, obtuse and entire process, which is generally somewhat incurved ; occasionally these processes are mere conical projections, but they may always be perceived. The end \-iew has from five to seven short, narrow, obtuse, marginal rays.
M. de Brebisson unites S. margaritaceum to S. dilatatum, but they appear to me to be distinct. In the front view of the latter the segments do not taper at their junction, are broader than long, and have no processes visible at the sides ; in all which respects it differs from S. margaritaceum.
Length of frond -j-jVb" °^ ^"^ ^"^^ '■> breadth, including processes, yoVo 5 breadth, excluding processes, ^stt 5 breadth at constriction -gaVg-.
Tab. XXI. fig. 9. a, b. front A-iews ; c, d, e. end views.
24. S. tricorne (Breb.) ; frond rough with puncta-like granules ; seg- ments tapering at each side into a short, blunt, mostly entire pro- cess ; end view with three or four blunt angles.
/3. Processes terminated by minute spines.
Binatella tricotmis, Brebisson, Jig. Fal. p. 57. t. 8 (1835). Desmidlum hexaceros, Ehr. Infus. ]). 141. t. 10. f. 10 (1838). Staurastrum tricorne, Meneghhii, Synop. Desmid. in Linncpa 1840, p. 225. Brebisson, in lit. cu7n icone.
BRITISH DESMIDIE.E. 135
Phycastrum triconie, Kutzing, Phycologin Germanica, p. 137 (1845).
DolgcUey and Penzance, J. R. Ambleside, Mr. Sidehotham. Cross-in- Hand, Sussex, Mr. Jenner.
fi. Penzance, /. R. Near Pulborough, Sussex, Mr. Jenner.
Falaise, Brehisson. Germany, Ehrenbery, Kitfziny.
Frond about as large as that of Stanrastrum alternans, deeply constricted at the middle ; segments in the front view somewhat fusiform ; in an end one showing three or four bhmt, generally entire angles.
The segments are frequently more or less twisted, in which case this plant bears a close resemblance to Staurastnim alternans ; but I retain the species in deference to the authority of INI. de Brebisson ; the tapering of the seg- ments at their sides is however its chief distinction.
The sporangia, which I have gathered at Penzance, are orbicular, and fur- nished with spines divided at the apex.
Length of frond yytt ^f an inch ; breadth ^^ ; breadth at constriction ■g^Lj- ; diameter of sporangium -^^ ; length of spines xxsT*
/3. Length of frond from y q'q^ to g\-^ ; breadth from y^^ to -^^ ; breadth at constriction -g^Vy '■> diameter of sporangium -gig- ; length of spines y^Vs •
Tab. XXn. fig. 11. a,b. front views of frond ; e. end view.
Tab. XXXIV. fig. 8. a. sporangium ; b. front view of var. |(3 ; c. end view ; d. sporangium,
tt Angles terminated by minute spines or tapering into slender
processes*.
25. S. polymorphum (Breb.) ; segments rough M-ith minute granules,
having on each side a short process tipped with spines ; end view
three- to six-rayed. Staurastnim jiolymorphum, Brebisson, in lit. (1846).
Dolgelley, J.iJ. Reigate, Surrey ; and near Pulborough, Sussex, Mr. Jenner.
Falaise, Brebisson.
Frond much smaller than that of Staurastrum yracile, deeply constricted at the middle ; segments irregular in form, bvit generally broader than long. Each side terminates in a short truncate projection or process, which is scarcely longer than broad, and tipped by three or four distinct, diverging spines ; frequently there are also a few inconspicuous scattered spines on the segment itself. The number of the angles or rays in an end view varies from three to six, but the four-rayed form is the most abundant. The size of the frond is proportionate to the number of these rays.
The sporangia, which I have gathered at Dolgelley, are orbicular ; their spines are few and forked at the apex. I have seen three-rayed fronds coupled with four-rayed ones.
* A variety of Staurastrum tricorne has the angles tipped by minute spines, and occasionally Staurastrum cyrtocerum is destitute of spines, excepting those terminating the processes ; both forms would therefore be referred to this section .
m
136 BRITISH DESMIDIE.E.
The segments are very variable in form and often resemble those of Stau- rastrum tricorne and S. margaritaceum, but in these species the processes are never spinous. S. polymorphum is smaller and less spinous than S. asperum.
Length of frond ^iroo ^f an inch ; breadth -^^ ; breadth at constriction .jJL_. ; diameter of sporangium -^-^ ; length of spine of sporangium -^-^.
Tab. XXII. fig. 9. a, b, c, d. front views ; e, f, g. dividing fronds ; h. end view of three-rayed segment ; i. transverse view of four-rayed segment ; h. end view with endochrome ; /. end view of empty frond.
Tab. XXXIV. fig. 6. a. front view of variety ; h. end view.
26. /S. gracile (Ralfs) ; segments rough, elongated on each side into a slender process which is terminated by minute spines ; end view triradiate.
Euastrum, No. 13, Bailey, Amer. Bacil. in Amer. Journ. of Science and
Arts, V. 41. p. 296. t. 1. f. 2-5 (1841). Staurastrum gracile, Ralfs, Annals of Nat. Hist. v. 15. p. 155. t. 11. f. 3
(1845) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 142. t. 14. Goniocystis {Trigonocystis) gracilis, Hassall, Brit. Freshwater Alg. p. 352
(1845).
Dolgelley and Penzance, /. R. Ambleside, Mr. Sidebotham. Aberdeen, Mr. P. Grant. Manchester, Mr. Williamson.
New York and New England, Bailey. Falaise, Brebisson.
Frond rough with minute granules, deeply constricted at the middle ; seg- ments two or three times longer than broad and tapering, on each side, into a slender, straight and colourless process, which is apparently terminated by three minute points : Mr. Jenner however informs me that the processes really terminate in four points, which are \isible only when a process pre- sents its extremity to the observer. The granules are arranged in trans- verse lines on the processes, and are here more conspicuous than they are on the segment. The end view is triradiate ; the colouring matter is restricted to the centre and forms three rays, which are frequently bifid.
Staurastrum gracile differs from S. tricorne in its elongated processes terminated by minute points. The end view somewhat resembles that of S. paradoxum, but the latter species is easily known by the divergent pro- cesses of its front view and its smaller size.
Length of frond from ^ka ^^ 'sk'^ *^^ ^" '\i\c\\ ; breadth from 3^^ to -^\-^ ; breadth at constriction axoT-
Tab. XXII. fig. 12. a. front view; b, c. end views; d. transverse view.
27. S. Arachne (Ralfs) ; segments rough with minute granules, sub- orbicular, with elongated, slender, incurved processes ; end view with five linear rays.
Staurastru7n Arachne, Ralfs, Annuls of Nat. Hist. v. 15. p. 157. t. 11. f . 6 (1845) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 143. t. 14.
BRITISH DESMIDIE^. 137
GoniocysHs (Pentasterias) amchnis, Hassall, Brit. Freshwater Ala. n. 355 (1845). ^ ^
Dolgelley, very rare, J. R. Aberdeen, Mr. P. Grant. Falaise, Bri^bisson.
Frond minute, deeply constricted at the middle ; segments about as long as broad, having on each side an elongated process, which is hyaline and incurved, and on account of its minute granules appears transversely striated. When the frond is viewed obliquely, so that three or more of the long curved processes are seen at once, its resemblance to an insect is considerable. The end view is circular with five slender rays.
This plant is remarkable for its slender processes, which will easily distinguish it from Staurastrum margaritaceum. It cannot be a five-rayed variety of ^. gracile or S. pohjmorphum, for its rays are longer, more slender, remarkably incurved and also entire at the extremity.
Length of frond -^^^-^ of an inch ; breadth, excluding processes, -^-^ ; including processes, -^ ; length of process -^-^ ; breadth at constriction
2 7 3 2'
Tab. XXIII. fig. 6. a. front view ; h. end view.
28. (S. tetracerum (Kiitzing) ; frond rough ; front view with four slender diverging processes which are entire at the apex ; end view compressed, with a process at each extremity.
Mierasterias tetracera, Kiitzing, Synopsis Diatom, in Linncea 1833, p. 602.
f. 83, 84. Mierasterias tricera, Kutzing, I. c. p. 602. f. 85. Staurastrum paradoxum,, Ehr. In/us. p. 143. t. 10. f. 14 (1838). Pritch.
Itifus. p. 185. f. 102, 103. Staurastrum tetracerum, Ralfs, Annals of Nat. Hist. v. 15. p. 150. t. 10.
f. 1 (1845) ; Trans, of Bat. Soc. of Edinburgh, v. 2. p. 137. t. 13. Goniocystis {Staurastrum 1) tetracei'um, Hassall, Brit. Freshwater Alg. p. 354
(1845).
Dolgelley and Penzance, J. R. Yate near Bristol, Mr. Broome. Aber- deenshire, Mr. P. Grant. Ambleside, Mr. Sidehotham. Midhurst, Battle, and Cross-in-Hand, Sussex, Mr. Jenner.
Germany, Kutzing, Ehrenberg . Falaise, Br^bisson. United States, Bailey.
Frond very minute ; front view nearly square, the angles elongated into straight, slender processes which diverge from each other ; frequently how- ever a segment may be so twisted, that one of its processes is situated behind its companion, and is not seen unless carefully looked for ; in this case the frond seems to have only three processes in a front view. The end view is much compressed and terminated both ways by an elongated process. The frond is rough with minute puncta-like granules, which form transverse lines on the processes and give them a jointed appearance. The colouring matter is very pale.
138 BRITISH DESMIDIE^.
Ehreiiberg and Meneghini unite the Micrasterias tetracera of Kutzing to the Staurastrum paradoxum, Meyen ; but whilst the latter plant has four processes at each end, this has only two, which, if I am correct in my view of the following species, differ also by having entire extremities.
Length of frond jtW ^^ ^'^ ^^^^ ' length of process -3 oVo 5 breadth of frond y^.
Tab. XXIII. fig. 7. a,b, c. front views ; d. empty frond ; e. frond with one segment not fully developed ; f. end view.
29. S. paradoxum (Meyen) ; frond rough ; front view with elongated diverging processes which are minutely trifid at the apex ; end view quadrangular or sometimes triangular.
/3. End view triradiate.
Staurastrum paradoxum, Meyen, Nov. Act. Leop. Holm. v. 14. p. 43. f. 37,
38 (1828). Meneghini, Synop. Besmid. in Linncea 1840, p. 227.
Ralfs, Annals of Nat. Hist. v. 15. p. 151. t. 10. f. 2; Trans, of Bot.
Soc. of Edinhurgh, v. 2. p. 137. t. 13. Micrasterias Staurastrum, Kutzing, Synop. Diatom, in Linncea 1833,
p. 599. Phycastrum paradoxum, Kutzing, Phycologia Germanica, p. 138 (1845). Goniocystis {Staurastrum) paradoxtim. Hassall, Brit. Freshwater Alg. p. 354
(1845).
Dolgelley and Penzance, J. R. Near Bristol, Mr. Thioaites and Mr. Broome. Ambleside, Mr. Sidebotham. Banffshire and Aberdeenshire, Mr, P. Grant. Near Pulborough, Cross-in-Hand, &c., Sussex, Mr. Jenner.
Germany, Meyen, Kutzing. Falaise, Brebisson. "West Point, New York, Bailey.
Frond verj' minute, generally mvich constricted at the middle, the ends truncate ; each segment has, generally, four elongated processes diverging from those of the other segment. The end view is sometimes triradiate, but usually quadriradiate ; I have also seen specimens in which one segment had four and the other only three rays. In the front view, as the frond generally rests on one side, each segment appears to have only two processes, the other two being covered by them ; but sometimes only one process is thus hidden, and occasionally all four may be seen at the same time. The processes are elon- gated, colourless, and, being rough with minute granules arranged in transverse lines, have a jointed appearance ; each terminates in three minute spines. In the newly-formed segment the processes are mere conical projections.
When only two processes are seen at each end, in the front view, this spe- cies is very like the preceding ; but its frond is more constricted, larger and of a deeper green, and its processes are thicker and not entire at the apex.
Length of frond ^y of an inch ; breadth i^wi '■> breadth at constriction ■^jjL- ; length of process from ^^ to y^.
Tab. XXIII. fig. 8. n, h, c. front views of mature fronds ; d, e. end view?; ; /'. immature frond.
BRITISH DESMIDIE^. 139
******** Frond spinous or rough with spine-like granules which are incrassated, emarginate, or divided*.
t Spines minute, inconspicuous and granule-like .
30. S. cyrtocerimi (Breb. ); frond rough with minute granules; seg- ments in the front view somewhat triangular with short incurved processes.
Euastrum , Bailey, American Jonrn. of Science and Arts, v. 41, t. 1.
f. 6 (1841). Staurastram cyrtocerum, Brebisson, in lit. cion icone (1846).
Dolgelley and Penzance, /. R. Near Bristol, Mr. Broome. Piltdown Common and near Pulborough, Sussex, Mr. Jenner.
United States, Baileij. Falaise, Brebisson.
Frond rather larger than that of Staurastrum tricorne, deeply constricted at the middle, rough with minute spine-like granules, which on the processes are arranged m transverse lines. The segments are truncate and taper towards their junction, so that the constriction forms a broad notch on each side. The spines on the outer margin are larger than those on the rest of the segment, and frequently are obscurely notched. The end view has three blunt angles, much like those of Staurastnwt tricorne, and usually a little curved.
The sporangia are orbicular and their spines slightly forked at the apex.
Staurastrum cyrtocerum is smaller than S. aculeatiim and S. controversum, and its spines are far less conspicuous. It is best distinguished by its con- verging processes.
Length of frond -^^ of an inch ; breadth -j^ ; breadth at constriction
1 •
2747 •
Tab. XXII. fig. 10. a. front view; 6. end view.
31. S. asperum (Breb.) ; segments elliptic or somewhat cuneiform, rough with minute spines, which on the outer margin are usually- dilated at the end or forked.
a. Angles in end view rounded.
/3. proboscidewn, Br^b. ; angles in end view prolonged into short
rays terminated by minute spines.
Staurastrum asperum, Brebisson, in lit. cum icone (1846).
Penzance, J. R. Yate near Bristol, Mr. Broome and Mr. Thwaites. Near Pulborough, Sussex, Mr. Jenner.
Falaise, Brebisson.
Frond comparatively large, rough with minute acute granules or spines ; segments slightly tapering on the inner side, so that their figure is somewhat cuueate, and the constriction forms a wide notch on each side. The outer
* Staurastrum polymorphum has occasionally a few scattered spines, but they are simple.
140 BRITISH DESMIDIE^.
margin is flattened, and its spines are usually more evident than the rest, and are also in general slightly forked. In a. the lateral margins are broadly roiuided, but in /3. they extend into a process about as long as broad and tipped with a few acute spines, which are larger than those on the segment itself. The end \iew, in which the sides are nearly straight, has the angles in a. rounded, but in j3. terminated by short rays.
The sporangia, which I have gathered at Penzance, are orbicular, and their spines are twice branched at the apex.
The form of the segments distinguishes Staurastrum asperum from all states of -S. muricatum. S . punctulatmn is smaller, and its granules are more like pmicta than spines. In S. rugulosum the segments in the front view are elliptic, not tapering at the junction, and its spine-hke granules are confined to the angles.
Length of frond -g^r of an inch ; breadth -g-ir ; breadth at constriction g-j^g-j ; diameter of sporangium -g-i^ ; length of spmes 3-5x0 •
Tab. XXII. fig. 6. a. front view ; b. end Adew.
Tab, XXIII. fig. 12. a. sporangium ; b. front view of variety (^ ; c. end view.
tt End view acutely triangular ; segments, in the front view, with a forked spine on each side, otherwise smooth.
32. S. Avicula (Breb.) ; segments with a forked spine on each side ; each angle, in end view, terminated by a mucro-like spine.
Staurastrum Avicula, Brebisson, in lit. cum icone (1846). Penzance, very rare, /. R. Falaise, Bi-ebisson.
Frond very minute, scarcely rough, the constriction producing wide trian- gular notches ; segments having on each side a spine forked like the tail of a swallow. End view with three slightly inflated angles or lobes, which are tipped by a spine.
The forked lateral spines of the front view mark the species.
Length of frond 9^^ of an inch ; breadth gig ; breadth at constriction 2X03^ > length of spine xwt%-
Tab. XXIII. fig. 11. a. front view; b. end view.
ttt Lobes in end view broad, emarginate or bipartite.
33. S. enorme ; frond irregular or quadrate, spinous; end view
three- or four-lobed ; lobes broad, more or less emarginate or bifid, and terminated by spines which are either simple or branched.
Dolgelley, J. B.
Frond very irregular and variable in form. Sometimes the front view diff"ers but little from the end one, usually however there is a slight con- striction or sinus at the junction of the segments, but I have never observed
BRITISH DESMIDIE^. 141
any differeuce in the endochrome at that part. The spines, which are almost confined to the angles, are irregular, some simple and some branched. The end \iew has three or four broad and very irregular lobes ; these are spmous and more or less emarginate, and frequently one lobe is much broader and more spinous than the others. The spines on each lobe form two groups separated by the notch ; they vary much in size, and are either simple and subulate or else forked ; sometimes the forked spines are again di\'ided at the apex.
Staurasfrum enorme is by far the least symmetrical plant in this family, especially in its front view, and it is very ditficult to trace any division into segments. In the end view the broadly emarginate lobes, which, exclusive of the spines, are truncate, afford a good specific distinction between it and any other species.
Length of frond ^-i-^- of an inch ; breadth of lobe in the end view -jxgy.
Tab. XXXIII. fig. 11. a, b, c. front views ; d, e. end i'iews.
tttt Spines nume?'ous, conspicuous ; angles in end view either rounded^ acute, or extended into processes.
34. S. spongiosum (Breb.) ; segments semiorbicular, spinulose; spines forked ; end view triangular, bordered with forked spines ; angles rounded.
Staurastrum spongiosum, Brebisson, Meneghini, Si/nop. Besmid. in Linncea
1840, p. 229. Brebisson, in lit. cum icone. Desmidium ratnosnm, Ehrenberg, Verhreitung und Einfluss des mikrosko-
pischen Lebens in Sud- und Nord-Amerika, t. 4. f. 21 ? (1843).
Penzance and Dolgelley, rare, J. B. Ashdown Forest, Sussex, Mr. Jenner. Falaise, Brebisson. "West Point, New York, Bailetj.
Frond large, about the size of that of Staurastrum muricatum, thickly covered with short spines, which are forked at the apex ; segments semiorbi- cular, havmg on each side one spine more conspicuous and more forked than the rest. End view triangular, fringed with short notched spines ; the sides are slightly convex and the angles rounded.
Staurastnan spongiosum is a very distinct species. In the front \'iew it has some resemblance to Xanthidium armatum, but is much smaller.
Length of frond from -^^ to -^-^ of an inch ; breadth from g-i-^ to j^-g- ; breadth at constriction from -A-^ to ^
3 8'
Tab. XXIII. fig. 4. a, b. front views ; c. end view. '
35. S. controversum (Breb.); frond spinulose; segments with a short process on each side terminated by minute spines ; end view with three or four distorted rays.
Staurastrum controversum, Brebisson, Meneghini, Synop. Desmid. in Linncea 1840, p. 228. Breb. in lit. cum icone.
142 BRITISH DESMIDIE^.
Staurastrum aculeatum, Ralfs, Annals of Nat. Hist. v. 15. p. 156. t. 11.
f. 4 (1845); Trans, of Bot. Soc. of Edinhurgh, v. 2. p. 142. t. 14.
Jenuer, Fl. of Tunhridge Wells, p. 194. Goniocystis {Trigo7iocystis1) aculeata, Hassall, Br. Freshwater Alg. p. 353
(1845). Dolgelley and Penzance, /. R. Reigate and Woking Common, Surrey ; Cross-in-Hand, Piltdown Common, &c., Sussex, Mr. Jenner. Yate near Bristol, Mr. Broome. Ambleside, Mr. Sidebotham. Aberdeen, Mr. P. Grant.
Falaise, Brebisson.
Frond deeply constricted at the middle ; segments broader than long, elliptic or fusiform, often irregular, but usually turgid on the inner side, laterally ta- pering into a short process, which is terminated by minute spines and generally curved or distorted. The end view is triangular or quadrangular, the angles terminating in short, truncate, curved processes, which, as in the front view, are tipped by miniite subulate spines. In both views the fronds show nu- merous conspicuous spines which are either subulate or notched at the end.
I formerly considered this plant to be the Staurastrum aculeatum, and I still doubt whether it may not be a variety of that species, which scarcely diflPers except in its processes, which are always straight.
Length of frond -g^-^ of an inch ; breadth from -^\-^ to yig ; breadth at constriction 3^^.
Tab. XXIII. fig. 3. a, b, c. front views ; d. end view of three-rayed form ; e. transverse view ; f. view of four-rayed variety ; g. transverse view ; h. spo- rangium from a drawing by Brebisson.
36. S. aculeatum (Ehr.) ; frond spinulose ; segments with a short process on each side terminated by minute spines ; end view with three to five straight rays terminated by spines.
Desmidiitm aculeatum, Ehrenberg, Infus. p. 143. t. 10. f. 12 (1838).
Pritchard, Infus. p. 184. Staurastrtim aculeatum, Meneghini, Sy7iop. Desmid. in Linncea 1840, p. 226. Phycastrum aculeatum, Kvltzing, Phycologia Germanica, p. 138 (1845).
Weston Bogs near Southampton ; and near Pulborough, Sussex, Mr. Jenner. Dolgelley, J. R. Ambleside, Mr. Sidebotham.
Germany, Ehrenberg . Falaise, Brebisson.
Frond about as large as that of Staurastrum conti'oversum, deeply con- stricted at the middle, the constriction producing a broad triangular notch on each side ; segments broader than long, somewhat fusiform, thickly spinulose, the spines simple or notched at the apex. The segments taper on each side into a short process tipped by three or four spines. The end view has from three to five short straight rays terminated by spines.
Length of frond -^ of an inch ; breadth -^\^ ; breadth at constriction 1
Tab. XXIII. fig. 2. a. front view; 6. end view of three-rayed form ; c. end view of four-raved variety.
BRITISH DESMIDIE.E. 143
37. -S^. spinosiun (Breb.) ; segments elliptic, furnished with a few bifid spines ; lateral spines solitary, larger and more forked ; end view triangular with two or three spines on each side and one terminating each angle.
Staiirastnim sjjuiosum, Brebisson, in lit. cum icone (1847).
Dolgelley and Penzance, J. R. Ambleside, Mr. Sidebothmn. Reigate, Surrey, Mr. Jenner.
Falaise, Brebisson.
Frond deeply constricted at the middle ; segments subelliptic, their outer margin usually more turgid than the inner ; on each side is a conspicuous sessile spine, forked like the tail of a swallow, and on the outer margin are a few smaller spines, which are usually forked at the end, though sometimes simple. End view triangular, each angle terminated by a spine, which ap- pears simple or forked according to its position when viewed ; sides with two or three spuaes, which are sometimes simple and sometimes forked, and on the upper surface are six other spines, one opposite to each lateral spine.
The sporangia of Staurastrum spinosum were first gathered by Mr. Broome near Bristol, and I have since fomid a few of them at Dolgelley. They are orbicular, and have numerous elongated spines which are divided at the apex.
M. de Brebisson considers this plant identical with the Xanthidium fur- catum, Ehr.
Length of frond -gJ-g of an inch ; breadth g-iy ; breadth at constriction 3/g^ ; diameter of sporangium ^^ ; length of spine of sporangium ^ ^'^ g .
Tab. XXII. fig. 8. a. front \'iew of frond ; b. end ^iew ; c, d. sporangia.
38. S. vestitum ; frond rough with minute emarginate spines;
segments fusiform ; end view triradiate, each side having two spines, short, slender, and often accompanied by other smaller ones.
Dolgelley, /. R. Near Pulborough, Sussex, Mr. Jenner.
Frond broader than long, about as large as that of Staurastrum gracile, deeply constricted at the middle, the constriction forming a triangular notch on each side ; segments somewhat fusiform, turgid on the inner margin, tapering at each side into a short process which is tipped by three or four mmute spines ; outer margin fringed with minute emarginate spines or tubercles. End -v-iew triradiate, showing also two slender forked spines at the middle of each side, whilst the margin is often fringed mth other spines, which are smaller and either simple or notched. The rays are elongate, rough with minute granules, and terminated by minute subulate spines.
In the end view Staurastrum vestitum resembles S. gracile in figure, but that species is not spinous. The rays in the end view are more slender than those of S. acideatum or S. controversum : but the most distinctive character of this species is the presence of a pair of slender forked spines at the midcUe of each margin.
144 BRITISH DESMIDIE^E.
Length of frond ^^ of an inch ; breadth 3-ij ; breadth at constriction i_
3 2 0 5'
Tab. XXIII. fig. 1. a. front view ; b, c. end views with endochrome ; d. end view of empty frond ; e. transverse view.-
12. DIDYMOCLADON, n. g.
Frond simple, constricted at the middle, angular, each angle having two processes, one lateral, and in front view nearly parallel to the ad- jacent one of the other segment, the other superior and divergent.
The frond is simple, constricted at the middle ; segments angular, as shown by the end view, each angle furnished with two elongated processes, the inferior lateral and nearly parallel to the similar one of the other segment, but the superior directed obliquely outwards and divergent.
This genus is closely allied to Staurastrum, but has one remark- able differential character. Each angle of the segments gives rise to two processes, one beneath the other, whereas in Staurastrum the process, when present, is solitary from each angle.
D. furcigerus, Breb.
a. End view triangular.
/3. End view quadrangular.
Staurastrum furcigeru7n,^x&o., Meneghini, Synop. Desmid. in Linncea 1840,
p. 226 ; in lit. cum icone. Phycast7'um furcigerum, Kiitzing, Phy. Germ. p. 138 (1845).
Dolgelley, J. R. Brookhouse Moss near Congleton, Cheshire ; and near Ambleside, Mr. Sidebotham. Rochdale, Mr. Coates. Brightling near Burwash, Sussex ; and Weston Bogs near Southampton, Mr. Jenner.
Falaise, Brebisson. Germany, Kutzing.
Frond comparatively large, rough with pearly granules, which being arranged on the processes in transverse lines, produce a crenate appearance on tlieir margins. In the front view the processes are elongated, stout, tapering, bifid at the apex. The lateral processes of the one segment are visually parallel to those of the other ; in Rochdale specimens however they are slightly curved outwards. The end view is triangular or quadrangular, and the elongated angles appear either acute and simple, or bifid, according as one or two forks of the processes may be \dsible.
Length of frond, including processes, 3-!^ of an inch ; length, excluding processes, y^y ; breadth, including processes, -^^ ; breadth, excluding pro- cesses, -g-i-5 ; breadth at constriction ^ g^g g .
Tab. XXXIII. fig. 12. a, b. front views; c. end view of a ; d. transverse view of /3.
BRITISH DESMIDIE^. 145
13. TETMEMORUS, Ralfs.
Frond simple, elongated, straight, cylindrical or fusiform, slightly
constricted at the middle ; segments emarginate at the end, but
otherwise quite entire.
The frond is elongated, as in Penium, from which however this genus may be distinguished by the emarginate ends ; the same character and the elongated frond will separate it from Cosmarium.
From Euastrum, with which it agrees in the emarginate extremities, it differs in being cylindrical or nearly so, and in the segments being neither lobed nor sinuated j the fronds are also free from inflated pro- tuberances.
Sporangia have been gathered of two species.
1. T. Brebissonii (Menegh.) ; frond in the front view with parallel sides, but in the lateral view fusiform ; the ends without any pro- jecting processes ; puncta in longitudinal lines.
/3. turgidus', larger, constriction greater; segments somewhat inflated.
Closterhim Brebissonii, Menegh. Syn. Desmid. in Linneea 1840, p. 236.
Closterium (sp. 9), Bailey, Amer. Bacil. in Amer. Journal of Science and Arts, vol.41, no. 2. t. 1. f. 38 (1841).
Tetmemorus Brebissonii, Ralfs, Ann. of Nat. Hist. v. 14. t. 8. f. 1 (1844) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 133. t. 12. Jenner, Fl. of Tnnbridge Wells, p. 198. Hassall, Br. Freshwater Alg. p. 377.
Closterium monile, Kiitzing, Phycol. Germ. p. 132 (1845).
Dolgelley ; Carmarthen ; Penzance, J. R. Sussex ; Kent ; Surrey and Hants, Mr. Jenner. Many stations in Aberdeenshire (alt. 50 — 3700 feet), Mr. P. Grant and Dr. Dickie. Banffshire, 3Ir. P. Grant. Ambleside, Mr. Sidebotham.
/S. Ashdown Forest, Sussex, Mr. Jenner.
Falaise, Brebisson. Germany, Kiitzing. Maine to Virginia, Bailey.
Frond four to six times longer than broad, with a slight constriction at the middle. The front view shows the lateral margins of the segments nearly straight, and their ends rounded and emarginate. The lateral view is more constricted at the middle and the segments are attenuated towards the end.
The endochrome is dark green, and there is a series of large vesicles down the middle m a single row, either straight or with some irregularity. The frond, when empty, is found to be minutely punctate, the puncta being ar- ranged in longitudinal rows.
The var. /3. somewhat approaches in form to Tetmemorus granulatus, but is more constricted at the middle, and the puncta form longitudinal lines.
146 BRITISH DESMIDIE^.
Tetmemorus Brebissonii differs from T. yranulatus in having its front and lateral views unlike each other, and its puncta arranged in longitudinal lines ; it is also generally smaller.
Length of immature frond 3-1^ of an inch ; hreadth y^Vs" '■> breadth at con- striction 1-bVs- ' length of mature frond -^ ; breadth -5-i^ ; breadth at con- striction -g-5-9.
Tab. XXIV. fig. 1. a. front view ; b. side view ; c. empty frond ; d, e. front and side views of var. j3 ; /. young frond.
2. T. lavis (Kiitzing) ; frond in the front view somewhat tapering, with truncate ends ; lateral view fusiform ; puncta none or very indi- stinct.
Tetmemorus granulatus (in part), Ralfs, Annals of Natural Hist. v. 14. t. 8.
f. 2. d, e,/,ff (1844) ; Trans, of Bot. Soc. of Edinburgh, v. 2. t. 12. Closterium Iceve, Kiitzing, Phycologia Germanica, p. 132 (1845).
Dolgelley, J. R. Aberdeen, Dr. Dickie. Ashdown Forest and near Tun- bridge Wells, Sussex, Mr. Jenner.
Germany, Kiitzing.
Frond four to six times longer than broad, constricted at the middle, tapering with straight sides ; ends truncate, with a hyaline lip, which is inconspicuous, and sometimes absent.
The puncta are so faint, that even when using the higher powers of Mr. Ross's achromatic microscope I have doubted their existence ; but Mr. Jenner and Mr. Ross assure me that they are scattered, as in Tetmemorus granulatus.
I have gathered the sporangia of this species for three successive years near Dolgelley, forming a mucous stratum on the moist soil ; I have also seen them mixed with Desmidiese sent from Aberdeen by Dr. Dickie.
After coupling, the segments of the fronds are separated by the formation of a large, quadrate, central cell, in which all the contents of both fronds are collected, the empty segments being loosely attached to its corners. The endochrome at first fills the cell, large starch globules being scattered through- out the miuutel}^ granular substance ; but at length it becomes a dense, round, homogeneous body of a dark green colour, which finally changes to an olive- brovni. In this stage the segments of the original fronds fall off, and leave the quadrate cell inclosing the sporangium. In the front \'iew, as stated above, the cell is nearly square ; the sides are concave, and the angles rounded and slightly produced. A lateral view shows that the cell and sporangium are both compressed.
In the present plant the process of forming the sporangium is interesting, as it exhibits a striking similarity to the change during the formation of similar bodies in Staurocarpus among the Conjugatte. In Stanrocarpus, after con- jugation, a subquadrate cell is formed, within which the endochrome is col- lected. The latter is at first of the same figure as the cell, but in one species at least is at length condensed into a compact globular body, and in every species the cell with the contained sporangium finally separates from the fila-
BRniSIl DESMIDIE.E. l47
tiients with which it is connected. In this separate state 1 can discover no character by which to distinguish the sporangium of Tetmemonis from one belonging to a species of Stattrocarpiis.
This plant is in size intermediate between Tetmemorus Bi'ebissonii and T. gramdatus. In figure it agrees with the former ; like the latter it has a hya- line lip, but one far less conspicuous. This character induced me, in my paper read before the Botanical Society of Edinburgh, to refer its sporangia to that species, and I did not discover my error imtil I had seen the true sporangia of T. granulatus.
Tetmemorus Icevis is distinguished from T. Brebissonii either by the absence of puncta or by their scattered state when visible ; its fronds also taper more in the front Anew. From T. granulatus it differs in being more constricted at the middle, and in havmg the front and lateral views dissimilar, irrespective of the terminal notch.
Length of frond from -^^ to -^^-^ of an inch ; breadth from yyxj ^^ ToTs > breadth at constriction from ytjt to ttjt 5 length of side of quadrate sporan- gium ,i^.
Tab. XXIV. fig. 3. a. front view; b. side view; c. empty frond; d, e,f. different stages of sporangium ; g. side view of sporangium.
3. T. granulatus (Breb.) ; frond fusiform both in the front and lateral views, and ending in a colourless projecting lip-like process.
Closterium granulatum, Brebisson, Menegh. Sgn. Desmid. in Linncsa 1840, p. 236. Kiitzing, Phy. Germ. p. 132.
Tetmemorus gramdatus, Ralfs, Annals of Nat. Hist. v. 14. t. 8. f. 2 (1844) ; Trans, of Bot. Soc. of Edinburgh, p. 134. t. 12. Jenner, Fl. of Tim- bridge Wells, p. 198. Hassall, Br. Freshwater Algce, p. 378.
Carnarvon; Dolgelley; Tal Sam near Lampeter, and Penzance, J.B. Sussex, Surrey, Kent and Hampshire, 3/r. Jenner. Kerry, Mr. Andrews. Hanham near Bristol, Mr. Thwaites. Charlton Fields, Manchester ; and Ambleside, Westmoreland, Mr. Sidebothatn. Aberdeenshire (alt. IGOO to 2455 feet). Dr. Dickie. Aberdeenshire and Banffshire (alt. 50 to 1600 feet), Mr. F. Grant.
Falaise, Brebisson. Germany, Kiitzing.
Frond fusiform, about six times as long as broad, and very slightly con- stricted at the middle. The extremities always have a colourless projecting lip-like process, which extends beyond the notch. The colouring is dark green, and a few large vesicles are arranged in a longitudinal row down the middle.
The empty frond is minutely punctated ; the puncta generally form one or two transverse lines in each segment near the central constriction ; in the other parts of the frond they are not in rows, but scattered.
Under a low power of the microscope this species much resembles the pre- ceding ; but it may always be distinguished by the front and lateral views being similar, and only differing in the terminal notch, which is not seen in the lateral view. There is also beyond the notch a remarkable lip-like pro-
148 BRITISH DESMIDIE.E.
jection, which is wanting in Tetmemorus Brebissonii, and the puncta seen in its empty frond are not arranged in longitudinal rows.
Tetmemorus granulatus differs from T. Icevis in its less constricted middle and its larger size. Its puncta too are usually very distinct, and the discovery of their respective sporangia leaves no doubt that these plants are distinct.
Its sporangia have been gathered by Mr. Jenner in Sussex, and by myself near Dolgelley. They differ considerably from those of T. Itsvis ; they are orbicular, and are not inclosed in a quadrate cell, but have the empty segments of the conjugating fronds loosely attached by an imperceptible membrane ; the margin of the sporangium is finely striated, a character which I have not noticed in Tetmemorus Icevis.
Length of frond from y-i^ to yts ^^ ^^ ^"^^ 5 breadth ^ g ; breadth at constriction from yts ^^ tts 5 diameter of sporangium from 3^ to 3^.
Tab. XXIV. fig. 2. a. front view ; b. side view ; c. empty frond.
14. PENIUM, Br^b. (in lit.)
Frond simple, elongatedj straight^ not, or but slightly, constricted ; segments entire.
The frond is cylindrical or elliptic and straight, with its opposite margins similar, its constriction none or very slight, and the suture at the junction of the segments is usually either indistinct or wanting. The segments are quite entire.
M. de Brebisson has constituted this genus for some plants which he separated from Closterium on account of their straight fronds, which have the opposite margins similar. It differs from Tetmemorus by the absence of a terminal notch, and from Cosmarium by its more elongated frond and its less marked constriction at the junction of the segments ; yet the cylindrical species of Cosmarium closely approach to this genus, and Cosmariwn turgidum and Cosmarium attenuatum are at least as much elongated as Penium truncatum.
Although the species in Penium are few, they present considerable differences in their characters. Some are smooth, and, like Closterium, have the endochrome arranged in longitudinal fillets, and at each ex- tremity of it a globule containing moving granules. Other species have a granulated surface, and there are two smooth and truncate which some botanists have referred to the Palmellcce.
Penium Digitus, on account of its size, is represented as magnified only 200 diameters.
BRITISH DESMIDIE.E. 149
* Empty frond either striate or granulate, generally reddish.
I . P. margaritaceum (Ehr.) ; frond cylindrical with rotundato-trun- cate ends ; pearly granules in longitudinal series.
a. Frond fusiform^ constricted at the middle ; granules distinct,
giving a denticulate appearance to the margin. /3, Frond linear, scarcely constricted at the middle; granules giving a denticulate appearance to the margin, somewhat scattered near the suture. y. punctatum ; frond linear, neither constricted at the suture nor denticulate at the margin ; granules appearing like puncta.
Closterimn maryaritaceum, Ehrenberg, Infus. p. 95. t. 6. f. 13 (1838). Me- neghini, Synop. Desmid. p. 236. Jenner, Fl. of Tunhridye Wells, p. 196. Kiitziug, Phy. Germ. p. 132. Hassall, Brit. Freshwater Alyce, p. 376.
Penium maryaritaceum, Brebisson, in lit. (1846).
a. Ashdown Forest, Sussex, Mr. Jenner. Penzance, J. JR.
/3. Near Bristol, 3Ir. Thwaites. Warbleton, Sussex, Mr. Jenner.
y. Dolgelley, J. R. Ashdown Forest, and Henfield, Sussex ; and Reigate, Surrey, Mr. Jenner. Near Aberdeen, Dr. Dickie and Mr. P. Grant. Am- bleside, Mr. Sidebotham.
Berlin, Ehrenhery. Falaise, Brebisson.
Frond minute, six to twelve times longer than broad, rough with pearly granules which are arranged in longitudinal rows. The forms which I have here considered varieties diifer so much, that it is probable they will prove to be distinct species. It will be seen that the variety /3. is intermediate between the extreme states, and since neither of our British forms agrees with Ehren- berg's figure and description, I shall describe each in detail.
a. Frond stout, rounded at the end, distinctly constricted at the middle ; fillets distinct, interrupted and, as well as the endochrone, divided into four equal portions by three pale transverse bands. Near each extremity there is an obscure globule ; segments somewhat fusiform. The empty frond is nearly colourless, and the pearly granules are distinct and give a denticulate appear- ance to the margin. Besides the middle transverse suture, there are two others corresponding with the interruptions of the endochrome. I have received this form from M. de Brebisson as his Penium maryaritaceum. It differs from Ehrenberg' s figure of Closterium maryaritaceum in being broader, more con- stricted at the middle, and having more ventricose segments. The arrange- ment of the endochrome and the position of the globules also differ.
The variety /3. agrees in colour -with the preceding, but it is shorter, and its sides are parallel. The granules are distinct, but less regular. I have only seen it after the endochrome had collapsed.
The variety y. is elongated, slender, linear, truncate at the ends, and scarcely constricted at the middle. The endochrome is divided into four portions by transverse pale bands ; but there are no fillets or globules with moving par- ticles. The empty frond is reddish, especially at its extremities, the last- formed segment being generally paler than the other. The pearly granules
L 2
150 BRITISH DESMIDIE^.
are very minute, and resemble puncta ; hence the margin of the frond is entire. The puncta or granules are arranged in longitudinal lines, hut those in the same line are so close together that they are nearly, if not quite, confluent ; in fact, unless a very high power of the microscope be used, the frond appears simply striate. Besides the central suture, several other transverse lines di^^lde the empty frond into compartments. This fonn agrees best withEhrenberg's figure of Closterium margaritaceum, but it is not denticulate at the margin.
Sporangia of y. have been gathered by myself near Dolgelley, and those of (j. by Mr. Thw^aites near Bristol. Both are orbicular, and situate betvpeen the deciduous fronds.
Length of frond in a. yig- of an inch ; breadth -g^ ; breadth at constric- tion YXsZ ; length of frond in y. yi-g ; breadth yiVs '■> diameter of sporan- gium ^.
Tab. XXV. fig. 1. a. frond of a. with endochrome ; b, c. empty fronds; d. empty frond of y. as seen under a low power ; e,/. fronds with endochrome ; ff, h. sporangia.
Tab. XXXIII. fig. 3. sporangium of /S.
2. P. Cylindrus (Ehr.) ; frond cylindrical with rotundato-truncate ends, rough with scattered pearly granules.
Closterium 1 Cylindrus, Ehrenberg, In/us. p. 95. t. 6. f. 6 (1838). Meneghini,
Si/nop. Desmid. p. 236. Kiitzing, Phy. Germ. p. 132. Penium Cylindrus, Bre'bisson, in lit. (1846).
Dolgelley, J. R. Ambleside, Mr. Sidehotham. Henfield ; Ashdown Forest, and Piltdovvai Common near Uckfield, Sussex, Mr. Jenner.
Berlin, Ehrenberg. Falaise, Brebisson.
Frond very minute, smaller than that of Penium margaritaceum, two or three times longer than broad, cylindrical with truncate ends, and rough with minute scattered granules or apiculi. As the covering is usually of a deep rusty red, it obscures the view of the endochrome. I have not observed any terminal globules.
Penium Cylindrus resembles P. margaritaceum in form, but is much smaller, and its pearly granules are scattered and not arranged in lines. The red co- lour of the empty frond is darker than that of any other plant in the family.
I have little hesitation in referring the British specimens to Ehrenberg's Closterium Cylindrus, although in their scattered granules they diifer from his and Meneghini' s descriptions.
Length of frond -~-^ of an inch ; breadth yyVo •
Tab. XXV. fig. 2. a. frond with endochrome ; b. dividing frond ; e. empty frond.
** Frond smooth, colourless. f Sporangium situated between the deciduous cells.
3. P. Digitus (Ehr.); frond smooth, elliptic-oblong M'ith rounded ends ; fillets obscure, undulated, interrupted only by a transverse band at the suture.
BRITISH DESMlDIE.i;. 151
Closterium Digitus, Ehr. Abh. der Berl. Ak. (1831), p. 68 ; Infas. p. 94.
t. Ci. f. 3 I Meueghini, St/nop. BesmicL in Linncea 1840, j). 23G. Bailey,
Amer. Bacil. in Amer. Joiirn. of Science and Arts, v.41 . p. 302. 1. 1 . f. 33.
Jcnner, FI. of Tunhridye Wells, p. 196. Hassall, Brit. Ahj. p. 376.
Kiitzing, Ph\j. Germ. p. 132. Closterium lamellosum, Brt'bisson, Alg. Fal. p. 59. t. 8 (1835). Pleurosicyos inyriopodus, Corda, Aim. de Carlsb. 1835, p. 125. t. 5. f. 68. Penium Digitus, Brebisson, in lit. (1847). Polysolenia Closterium, Ehr. MS. Bailey, m lit.
Very common. Wales and Penzance, /. R. Sussex, Surrey, Kent and Hants, Mr. Jenner. Kerry, Mr. Andrews. Near Bristol, Mr. Thivaites. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Banffshire, Mr. P. Grant. Ambleside, Mr. Sidebotham.
Germany, Ehrenberg, Kiitzing, Corda. Falaise, Brebisson. Maine to Virginia, Bailey.
Froad smooth, stout, three to five times longer than broad, elliptic or ellip- tic-oblong ; not unfrequentlv however the frond is dilated at one end and becomes ovato-oblong ; the ends are broadly rounded. The endochrome is yellow-green with a pale transverse band at the middle ; there are no regular fillets, but longitudinal undulations are more or less perceptible. Terminal globules wanting, or very indistinct, in British specimens. The end view is circular, and the endochrome radiate. The empty frond is colourless, flexible, and without markings.
Ehrenberg' s description and figure of his Closterium Digitus is unlike the plant here described, and Brebisson formerly supposed it was intended for the next species ; but the whole ovitline and the description of the rounded ends are certainly more suitable to this. I have never seen any terminal vesicles, yet they are depicted by Ehrenberg and also by Professor Bailey in a figure in his 'American Bacillaria.'
In the recent state there can be no danger of confounding Peniuin Digitus with P. interrvptum ; and even in the dried state, although the conspicuous differences dependent on the disposition of the endochrome are no longer to be found, the form of the frond appears to me a sufficient distinction.
Length of frond -^ of an inch ; greatest breadth -^^.
Tab. XXV. fig. 3. a, b. fronds with endochrome ; c. empty frond.
4. P. interruptum (Breb.) ; frond smooth, cylindrical ; extremities conical with rounded apex ; fillets strongly marked, interrupted by three transverse bands.
Penium. interruptum, Brebisson, in lit. (1846).
Dolgelley and Penzance, J. R. Ashdown Forest and Chiltington Common, Sussex, Mr. Jenner. Ambleside, Westmoreland, Mr. Sidebotham.
Falaise, Brebisson.
Frond stout, four to six times longer than broad, quite straight, cylindrical, so that the sides are parallel, except at the extremities, which are rather sud- denly conical and rounded at the apex. Endochrome dark green ; fillets straight, three or four strongly marked and a fainter one near each margin.
152 BRITISH DESMIDIEJE.
Besides the central transverse band present in all the Desmidieae, Penium inter- ruptum has two others ; the fillets and endochrome are consequently divided into fonr portions. The ends are colourless, and each is partly occupied by a large globule, which contains moving granules like those in Closterimn. The empty frond is colourless without markings, and there is no transverse line at the middle.
In a recent state this is a remarkable plant. The fillets are more strongly marked than in any other species I have met with, and the checkered appear- ance produced by the transverse bands essentially distinguish it. It must however be observed that this character is lost in the dried state, when its straight, cylindrical fronds have some similarity to those of Penium Digitus ; but they are longer in proportion, their sides more parallel, and their extre- mities more conical.
Length of frond y^r of an inch ; breadth y^.
Tab. XXV. fig. 4. a. frond magnified 400 times ; b. frond magnified 200 times.
5. P. closterioides ; frond smooth, lusiform or lanceolate; lon- gitudinal fillets and terminal globules distinct.
Penzance and Dolgelley, J. R. Ash down Forest, and Piltdown, Sussex ; Reigate, Surrey ; and near Southampton, Mr. Jenner.
Frond six to ten times longer than broad, straight, lanceolate ; end obtuse ; fillets and tei-minal globules distinct ; vesicles in a single longitudinal series. Empty frond colourless and without markings.
Penium closterioides in its appearance and in the arrangement of its endo- chrome agrees better with Closterium than with Penium, and strongly resem- bles the side view of some species of the former. The frond however is always straight, and the opposite margins are symmetrical.
Length of frond -^-^ of an inch ; breadth g-g-^ .
Tab. XXXIV. fig. 4. a. frond with endochrome; b. empty frond.
G. P. truncatum (Breb.) ; frond smooth, cylindrical with truncate
ends; sporangia orbicular, easily detached from the conjugated
fronds. Cylindrocystis truncata, Brebisson, in lit. cum icone (1847).
Dolgelley, J. R.
Falaise, Brebisson.
Frond very minute, two or three times longer than broad, smooth, cylin- drical with truncate ends, sometimes slightly constricted at the middle. The endochrome is similar to that of Penium Brebissonii, but the transverse pale band at the middle is usually more distinct.
The empty frond is colourless, and its suture imperceptible. I believe that it is minutely dotted, but the dots are too indistinct to assist in defining the species.
I have gathered (he sporangia rather abundantly in a pool near Dolgelley ;
BRITISH DESMIDIE.E. 153
they are orbicular and situated between the conjugating fronds, from which, after their formation, they soon become detached,
Penium tnmcatum closely resembles a small specimen of P. Brehissonii, but it is much smaller and its ends are truncate. In form it agrees with P. Cylin- drus, but in that species the empty frond is coloured and distinctly granulate.
Length of frond from g^ to -^\-g of an inch ; breadth from 2-2V2 *« -oT^o^ 5 diameter of sporangium -^\^.
Tab, XXV. fig, 5. a, b, c. mature fronds ; d. dividing frond ; e. conjugated fronds ; f, g. sporangia.
7. P. Jenneri ; fi'ond smooth, cylindrical with rounded ends ;
sporangium orbicular, situated between the conjugating fronds, which are deciduous.
Bogs at Fisher's Castle, Tmib ridge Wells, Mr. Jetiner.
Frond variable in length, from two to four times longer than broad, oblong or cylindrical with rounded ends,
I know no character by which to distinguish the usual state of Penmm Jen- neri from P, Brebissonii. They agree in size and form ; in both the arrange- ment of the endochrome is similar, and the transverse pale band at the mid- dle is often indistinct ; the empty frond also is smooth and colourless, and no suture can be detected. Still the diiferent fonns of their sporangia compel us to consider them as distinct species.
In the present plant the conjugating fronds do not open and gape at the suture, as is usual in the Desmidiese, but couple by small and distinct cylin- drical tubes, like many in the Conjugatee. The sporangium is orbicular, and situated between the fronds, withhi the dilated connecting tube.
The frond in Penium Jenneri is more rounded at its ends and larger than those of P, truncatum ; in the latter species, moreover, the conjugating cells gape at the suture ; in both they are but slightly attached to the sporangium.
Length of frond from -^^ to ^3^ of an inch ; breadth from i^^Vt ^^ tbW 5 diameter of sporangium x^o^-
Tab, XXXIII, fig. 2, a, b, e, e. fronds with endochrome ; d. empty frond ; f. dividing frond ; g. conjugated fronds ; h, i. mature sporangia,
tt Sporangium permanently attached to the conjugated cells, at first quadrate, then orbicular (Cylindrocystis).
8. P. Brebissonii (Menegh.) ; frond smooth, cylindrical with rounded ends, transverse central band inconspicuous ; sporangium at first quadrate but finally orbicular ; conjugating fronds persistent.
Palmella cylindrospora, Brebisson, Alg. Fal. p. 64 (1835).
Cylindrocystis Brebissonii, Meneghini, Cenni suUa organografia e fisiol. delle Alg. pp. 5, 26 (1838) ; Monog. Nost. t. 12. f. 3. Hassall, Brit. Fresh- water Alg. p, 361. t. 92. f. 17.
Cymbella? Icetevirens, Harvey, Man. of Brit. Alg. p. 216 (1841).
Closterium Cylindrocystis, Kiitzing, Phy. Germ. p. 132 (1845).
154 BRITISH DESMIDIE^.
Very common, especially where water lodges in wet weather. Cornwall and Wales, /. R. Ayrshire, Rev. B. Landshorough. Aberdeenshire and Banff- shire, Br. Bickie and Mr. P. Grant. Northamptonshire, Rev. M. J. Berkeley. Sussex, Kent, Surrey, and near Southampton, %Ir. Jenner. Ireland, Mr. An- drews. Essex, Mr. Hassall. Near Bristol, Mr. Thwaites and Mr. Broome. Westmoreland, Mr. Sidebothum. Rochdale, Mr. Coates.
Falaise, Brebisson. Germany, Kiitzing. Princeton, New Jersey, with sporangia, Bailey.
Frond minute, often congregated into a mucous stratum on wet mud, in the same manner as Tetmemorus gramdatus, its frequent companion, which at first sight it resembles. The fronds vary much in size, from two to six times longer than broad, and are oblong or cylindrical with rounded ends. The transverse pale central band, which in the Desmidiese indicates the suture or junction of the segments, is less conspicuous here than in any other plant of the family. The endochrome being usually denser at the middle of each seg- ment produces a resemblance to a joint of a species oiTyndaridea. The end view is circular with a central nucleus. The empty frond is smooth and co- lourless ; no suture can be detected in it. The sporangia have been gathered by me at Dolgelley ; by Mr. Jenner on Piltdown Common and near Tunbridge Wells, Sussex, and by Mr. Thwaites near Bristol. The process of conjugation in this species differs from that in the rest of this genus ; for, as in Hyalotheca dissiliens, the conjugating cells enter into the formation of the containing cell and are permanently attached to the sporangium, instead of being at length detached, as commonly happens in the Desmidiese. The sporangium is at first cruciform, then quadrate, and finally orbicular,
Penium Brebissonii has been placed with the Palmellese by Meneghini and Brebisson, because the division into two segments is but obscurely indicated, and its fronds often form a mucous stratum, I cannot however concur with them, and I consider that it has been correctly removed by Kiitzing to this family. Tetmemorus grunidatus, Cosmarium curtxim, and other undoubted Desmidieae, form similar strata, are often mingled with it, and by the naked eye cannot be distinguished from it. In its formation of sporangia this plant also agrees with the undoubted members of the family.
That this species has been referred to the Palmellese by such distinguished algologists proves indeed how closely the families are allied. M. de Brebis- son, in a recent letter, admits that it may belong to the Desmidiese, but con- siders that the difference in the formation of its sporangia is a sufficient rea- son for keeping the genus. Admitting that in strictness his view is correct, I nevertheless place this species in Penium, because the conjugated state, occur- ring so rarely, would seldom enable the student to distinguish between Penium and Cylindrocystis.
Length of frond from ^-|y to jij of an inch ; breadth from xtVf ^^ "sir '■> length of side of quadrate sporangium from y^ to -g-^j- ; diameter of mature sporangium -^-^.
Tab. XXV, fig. 6. «, h. fronds with endochrome; r, d. empty fronds; e, f, (J. imperfect sporangia ; h, i. mature sporangia.
BRITISH DESMIDIE^E. 155
15. DOCIDIUM, ^re6.
Frond simple, straight, much elongated, linear, constricted at the middle and truncate at the ends ; segments usually inflated at the base.
Fronds simple, straight, much elongated, sometimes even twenty- times longer than broad, constricted at the middle, where the suture is generally very distinct in both living and empty fronds. In almost every species the segments are inflated at their base ; the ends are truncate.
Professor Bailey has been very successful in adding new and cu- rious species to this genus, some of them differing greatly from any previously known.
Docidium, like Closterium, has terminal globules containing moving granules, and its vesicles are either scattered or arranged in a single longitudinal row.
It differs from Closterium in its straight fronds and constricted middle ; and from Penium it may be known by having a distant con- striction at the middle and more elongated fronds.
1. D. nodidosum (Breb.) ; frond stout; segments four to six times longer than broad, constricted at regular intervals so as to produce undulated margins ; sutui'c projecting on each side.
Closterium Trabecula, Bailey, Amer. Bacil. in Amer. Journ. of Science and
Arts, V. 41, p. 302. t. 1. f. 32? (1841). Docidium nodulosum, Brebisson, in lit. cu7n icone (1846).
Dolgelley, /. R. Durdham Down near Bristol, Mr. Thwaites. Aberdeen- shire, Dr. Dickie and Mr. P. Grant. Ambleside, Westmoreland, Mr. Side- hotham. Henfield, Sussex, and near Southampton, Mr. Jenner.
Falaise, Brebisson. Maine to Virginia, Bailey.
Frond large, distinctly visible to the naked eye, beam-like, constricted at the middle, where the thickened suture projects on each side like an apiculus. Segm.ents about four times as long as broad, scarcely attenuated, regularly in- flated at intervals, whence the margins appear undulated ; the basal inflation is the most prominent, the others less so as they are situated nearer the end ; often only two or three nearest the base are distinct, but occasionally as many as eight undulations may be counted at the margin.
Docidium nodulosum differs from D. constrictum, Bailey, and D. nodoswn, Bailey, in its more numerous but slighter constrictions. In both these species the inflations are always four, conspicuous, and more distant. In D. verru- cosum, Bailey, the segments are longer in proportion to their breadth ; the un-
156 BRITISH DESMIDIE^.
dulations, which are more numerous and equal, depend on the presence of whorls of small tubercles. In D. coronatum, Brel)., the apex behig encircled by a series of small tubercles, the end view is crenate.
Length of frond -g\ of an inch ; breadth -^ ; breadth at hiflation -^ ; breadth at end ■^^.
Tab, XXVI. fig. 1. a. frond with endochrome ; b, empty frond.
2. D. truncatum (Breb.) ; frond stout ; segments three or four times longer than broad, with a single inflation at the base, tapei'ing to the truncate entire ends ; suture projecting on each side.
Closterium truncatum, Breb. Meneghini, Synop. Desmid. in Linncea 1840,
p. 235. Docidium truncatum, Brebisson, in lit. cum icone (1846).
Carnarvon and Penzance, /. R. Hastings, Sussex, and Brookland near Reigate, Surrey, Mr. Jenner.
Falaise, Brebisson. Germany, Kiitzing.
Frond cylindrical, stout, distinctly constricted at the middle, the suture forming a thickened rim, which pi'ojects on each side like a small point. Seg- ments three or four times longer than broad, slightly inflated at the base and tapering towards the end, which is truncate and entire.
Docidium truncatum seems to me to approach closely to D. nodulosum, with which it agrees in size. Its distinctive marks are the more attenuated extremities and the solitary inflation at the base of each segment, so that its margins are not undulated. Mr. Jenner considers them as undoubtedly distinct, but to which dried specimens belong I am occasionally unable to decide ; for in drying, fronds of D. nodulosum frequently become attenuated at the ends, and sometimes only the basal inflation can be seen. Its larger size, short- ness of the segments in comparison with their breadth, and the distinct projec- tion of the junction-rim on each side, sufficiently distinguish D. truncatum from D. Ehrenbergii.
Length of frond from -^ to -jL. of an inch ; greatest breadth from -^^ to ■^^ ; breadth at constriction -g-iy ; breadth at end from yjVs ^o q^to •
Tab. XXVI. fig. 2. a. frond with endochrome ; b. empty frond.
3. D. clavatum (Kiitz.) ; segments many times longer than broad, with a single inflation at the base ; end clavate, but truncate at the apex.
Closterium truncatum, Kutzing, Phy. Germ. p. 133 (1845), nee Breb. Docidium clavatum, Kiitzing, in lit. cum icone (1840). Brebisson, in lit. cum icone et spccimine.
Midhurst, Sussex, Mr. Jenner.
Germany, Kiitzing. Falaise, Brebisson.
Frond longer than those of the first two species, but more slender, constricted at the middle ; the suture strongly marked, but not projecting at the margin.
BRITISH DESMIDIE.E. 157
Segments eight to twelve times longer than broad, gradually thickened near the ends in a clavate manner, the end itself being slightly attenuated and truncate ; there is a single inflation at the base. Vesicles small, few, and arranged in a single longitudinal line. The empty frond is minutely pvmctate, but the highest powers of the microscope are required to detect the puncta.
BreTjisson's specimens are more clavate than British ones, or than Kiitzing's plant appears in a drawing received from him.
Length of frond -^ of an inch ; breadth ^J-j ; breadth at inflation g-L • breadth at end ytts'
Tab. XXVI. fig. 3. a. frond with endochrome ; b. empty frond from French specimen.
4. D. Ehrenbergii ; segments many times longer than broad,
having two or three slight inflations at the base and truncate ends bordered by minute tubercles.
|3. granulatum ; frond rough with minute granules.
Closterium Trabecula, Ehr. Abh. d. Berl. Ak. (1830), p. 62; Infus. p. 93. t. 6. f. 2. Meneghini, Synop. Desmid. p. 235. Kiitzing, Phycologia Germanica, p. 133? Jenner, Flora of Tunbridge Wells, p. 196.
Dolgelley, Carnarvon, Penzance, &c., J. R. Several stations in Sussex ; and near Southampton, 3Ir. Jenner. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Ambleside, Mr. Sidebotham.
/3. Henfield, Sussex, Mr. Jenner. Penzance, J. R. Germany, Ehrenberg, Kiitzing. Falaise, Brebisson.
Frond as long as those of Docidium nodulosum and D. truncatum, but far more slender, constricted at the middle ; the suture strongly marked, but ha-sing no projection at the mai'gins. Segments eight to twelve times longer than broad, having about two slight inflations at the base, but otherwise linear. The end is truncate, and three to five minute tubercles, which may be detected at its margin, give the end view a crenate appearance. The empty frond is punctate, but in general the puncta are not readily discerned. Mr. Jenner finds in Sussex a variety the -frond of which is distinctly granulate.
I have gathered the sporangia at Penzance for two successive years ; they are large, suborbicular or elliptic, but often slightly angxilar, and are situated between the conjugating fronds, from which they easily separate.
Docidium Ehrenbergii in size equals D. clavatum, but it is not clavate, and its ends are bordered by minute tubercles. In the latter character it cor- responds with D. coronatum, Breb. ; but it is much smaller and the suture does not project at the sides.
Length of frond from ^^ to jL of an inch ; breadth from yyyt *^ gir 5 breadth at inflation from -g^ to -^ ; breadth at end yxrj '■> diameter of sporangium -arr-
Tab. XXVI. fig. 4. a. frond with endochrome ; b. dividing frond ; c. empty frond; d. conjugating fronds ; e,f. sporangia.
Tab. XXXIII. fig. 4. empty frond of variety ft.
158 BRITISH IJESMIDIE^.
5. D. Baculum (Breb.) ; segments very slender, having a solitary and conspicuous inflation at the base, otherwise linear ; vesicles in a single series.
Closterium Baculum, Brebisson, Alg. Fal. p. 59. t. 8 (1835).
Closferium trabeculoides, Corda, Observ. Microscop. sur les Animal, de
Carlsbad, t. 6. f. 44 (1840). Closterium Sceptrum, Kiitzing, Phycologia Gertnanica, p. 133 (1845). Docidimn Baculum, Brebisson, in lit. cum icone (1846).
Common. Carvarvon ; Dolgelley ; near Lampeter ; Penzance, &c., /. R. Ashdown Forest ; near Storrington, &c., Sussex, Mr. Jenner. Near Bristol, Mr. Thivaites and Mr. Brootne. Aberdeenshire, Dr. Dickie and 3Ir. P. Grant. Ambleside, Mr. Sidebotham. Rochdale, Mr. Coates.
Falaise, Brebisson. Carlsbad and Prague, Corda. United States, Bailey.
Frond very slender, many times longer than broad, distinctly constricted at the middle. Suture strongly marked, but hav-ing no projections at the mar- gins. Segments with a solitary inflation at the base, otherwise hnear, the ends truncate and without tubercles.
Docidium Baculum may be readily recognized, as it is more slender than any of the preceding species, and its inflations are more developed.
Length of frond yIt ^^ ^^^ ^^^'^^^ ' greatest breadth yttt » breadth at m- flation YoVs ? breadth at end ^^^.
Tab. XXXIII. fig. 5. a, b. fronds with endochrome ; c. empty frond mag- nified 400 times.
6. D. minutwn ; frond slender, slightly constricted at the middle;
segments linear, not inflated ; vesicles in a single series.
Dolgelley, /. R. New Forest, Hants ; and Parham Old Park near Stor- rington, Sussex, Mr. Jenner.
Frond minute, smaller than those of any of the foregoing species, linear, the constriction often scarcely perceptible ; segments four to six times longer than broad, the ends truncate.
The smaller size and uuinflated state of Docidium minutum distinguish it from D. Baciilum.
Length of frond ~-t of an inch ; greatest breadth yttj-
Tab. XXVI. fig. 5. a. frond with endochrome; b. empty fi-ond.
7. D. ? asperum (Breb.) ; frond slender, cylindrical, rough with minute scattered granules, neither constricted nor inflated at the middle ; ends truncate and dilated.
Docidium asperum, Brebisson, in lit. ctmi icone (1846).
Kerris near Penzance, J. R.
Falaise, Brebisson.
Frond slender, twelve or more times longer than broad, rough with scat- tered minute points which are best seen at the margins. Endochrome irre- gular. I have seen neither vesicles nor terminal globules.
BRITISH DESMIDIEiE. 159
I am doubtful whether this plaut be a true Docidium, for in all the other species of this genus there is, at the middle, an evident constriction, and a conspicuous suture where the segments eventually separate ; on the other hand, this plant has neither constriction nor suture.
Specimens of Docidium aspennn sent me bvM. de Brebisson are attenuated towards the extremities, whilst the apex itself is dilated. British specimens are not constricted beneath the dilated ends. Brebisson finds moving granules at the extremities as in the other species, but I have not noticed them.
This plant is not unlike the separated joints of a species of Mougeotia, but
the dilated ends and roughness produced by minute granules distinguish it.
Length of frond from J^ to ^ of an inch ; breadth j^Vb" '■> breadth at end 1
2 27 2"
Tab. XXVI. fig. 6. a. frond wdth endochrome ; h. empty frond ; c. empty frond of French specimen.
16. CLOSTERIUM,A^i/^5c^.
Frond simple, elongated, attenuated, Innately curved or arcuate,
entire ; the junction of the segments marked by a pale transverse
band.
In Closteriwn the frond is simple, much elongated_, fusiform, rarely cylindrical or prismatic, more or less attenuated at the extremities. It is semilunate, crescent-shaped, or, in a few instances, curved only at the ends, but in the usual position the opposite margins are always more or less dissimilar, the upper one being convex, and the lower, inclusive of the ends, straight, or more commonly concave ; the lateral view, which differs from the front one, is straight and has both mar- gins similar. As happens in the allied genera, the frond is composed of two segments which finally separate and allow the escape of the endochrome ; the suture or junction is marked by a transverse hyaline or pale band, accompanied in some species by one or more transverse striae, best seen in the empty frond ; but there is no constriction. The segments are entire, without spines, processes, or inflated pro- tuberances.
The endochrome is green with darker longitudinal bands or fillets? the number of which varies in different species. Meneghini considers them of too much importance to be omitted in the specific definition*. They may occasionally be useful in discriminating nearly allied forms,
* " Interanea initio uniforma serius in tsenias distribuuntur, quarum cha- racteres constantes videntur et in specifica definitione omitti nequeunt." — Menegh. Synop. Desmid. p. 230.
160 BRITISH DESMIDIEiE.
but as they are frequently indistinct, or from various causes it may be difficult to count them with certainty, I am unwilling to introduce them into the specific character except in the absence of more per- manent marks of distinction.
The diaphanous vesicles, which are conspicuous in most of the species, are either scattered or arranged, with more or less regularity, in a single longitudinal series.
At each extremity of the endochrome, even in its earliest state, there is a large hyaline or straw-coloured globule, M'hich contains minute granules in constant motion. This globule disappears in the dried specimen.
A distinct circulation has been noticed in several species. It is said to occur only in specimens obtained from water, and not in those taken from moist ground.
The empty frond is striated in some species and smooth in others, but no instance of its being granulate is known. The striated species are by Ehrenberg placed together in a subgenus {Toxotium), but it is sometimes very difficult to detect the striae, which I have also seen distinctly in Closterium attenuatum, and other species usually considered smooth.
The colour and firmness of the covering differ in different species. Some are quite colourless, flexible, collapsing when dried, and in general allowing the endochrome to escape by a merely partial sepa- ration of the segments. These species are never striated. In other species the fronds are more or less straw-coloured or even reddish, probably from the presence of a small portion of silicate of iron. The deeper the colour the firmer is the frond. The segments separate entirely from each other and retain their shape when empty or dried ; and some of the striated species, even when submitted to the action of nitric acid or fire, retain their form and markings. In the coloured species the extremities are generally darker than the rest of the frond.
Even in the firmest species the frond becomes flattened in drying, its breadth at the centre increases, and the ends appear more atte- nuated than in their living state. This fact should be attended to when describing or drawing a dried specimen.
In Closterium, of which several species have been noticed in a conjugated state, the process appears to be nearly the same as in the Conjugatae. Two fronds unite by means of projections arising at the
BRITISH DESMIDIE.*:, 161
junction of the two segments, and then the newly-formed portion continues to enlarge until the original segments are separated by a cell of an irregular four-sided figure. The contents of the fronds, being collected in this cell, become a dense seed-like mass, which is sometimes globular resembling the sporangium in Mougeotia, and sometimes square like that in Staurospermum. The newly-formed cell is thinner and generally paler than the segments of the frond ; in some species it looks like a prolongation of the segments, and in others these are so loosely attached that their connection is scarcely perceptible.
Two species having cruciform or quadrate sporangia permanently attached to the empty segments of the conjugated fronds are separated by Kiitzing to form a new genus, Stauroceras. To these others have been added by Brebisson. Whilst fully admitting the soundness of the principle on which this separation has been made^ I regret that I am unable to adopt it here, not only because I am uncertain to which genus some of the species should be referred, but because I have decided to employ in this monograph only such generic characters as can be determined in the ordinary state of the plant, and will not oblige the observer to depend on conditions which he may not be able to discover.
According to Meneghini the coupling of the fronds takes place from the convex margin. This is generally, but not invariably, the case, for I have observed that they are connected sometimes on the convex and sometimes on the concave margin ; in some instances, in- deed, I have seen the convex margin of one frond connected with the concave margin of another. Mr. Jenner has noticed the same diversity, but it appears to him to characterize different species.
As there is no constriction in Closterium, although its frond divides like that of other Desmidieee, the process of division is less evident. It is best seen in the striated species, in which the central suture is most distinct. The transverse line becomes double, and by the in- termediate growth the frond at length consists of three portions. As the newly-formed central one continues to elongate, another transverse line becomes visible at its middle, where a complete separation at length takes place. At first however the new segment is often merely a rounded protuberance, and the frond is consequently unequal ; and when it is perfected, if the covering is a coloured one, the newer seg- ment can still be distinguished by its greater paleness.
162 BRITISH DESMIDIE^.
The striated species, besides the central suture, frequently have other transverse lines that divide the segments themselves into two or more portions. Brebisson considers that their number is constant in the same species, and that they may be used in framing a specific character ; but my experience leads me to agree with Meneghini, that it is generally unsafe to place much reliance upon them : nevertheless it must be admitted that in many species no other suture than the central one is ever present, except during the process of division.
Closterium may be distinguished from all the other genera of the Desmidieag by its elongated, curved, entire, and attenuated fronds.
I have divided Closterium into sections answering to the genera of Kiitzing and Brebisson, according to a list of the species sent me by the latter ; but I must notice that one or two species wull probably be found to agree just as well with some other section as with that in which it is placed.
In the first section the fronds are commonly either semilunate or crescent-shaped, and have the extremities blunt or but moderately elongated ; the terminal globules are situated so near the ends that the endochrome nearly fills the cell ; the extremities appear to have a slight notch or depression (the opening of Ehrenberg) ; the spo- rangia are orbicular, and are situated between the conjugating fronds and but slightly connected with them.
The second section contains but one species, which by Brebisson is still retained in Closterium ; the form however of its frond agrees with that of Kiitzing's Stauroceras, whilst its sporangium is unlike that of any other species. The fronds are inflated at the middle and elono-ated at each end into a short curved beak, and there is no notch apparent at the ends. The sporangium, which is placed between the conjugating cells, is geminate, consisting of two nearly orbicular portions, flattened at their junction, where they often separate.
The plants in the third section are in general curved only at their extremities, which taper considerably, and frequently form a slender beak. The margins of the frond, exclusive of the curved extremities, are in most cases nearly similar ; the moving granules are more or less distant from the extremities, which have no distinct terminal notch ; and the segments are permanently attached to the sporangium, w hich is cruciform or quadrate.
BRITISH DESMIDIE^. 163
^ Sporayigium orbicular, situated between the conjugating fronds and but slightly connected with them ; fronds never rostrate. (Closte- rium.)
t Frond semilunate or semilanceolate, tapering from the middle, the lower margin straight [or nearly so) and inclined upwards at the end.
1. C. Lunula (Miiller) ; frond smooth, semilunate; lower margin nearly straight, inclined upwards at the rounded ends ; vesicles numerous, scattered.
Vibrio Lunula, Miiller, Naturforsch. p. 142 (1/84) ; Animal. Infus. p. 55.
t. 7. f. 13 and 15. MuUeria Lunula, Leclerc, Mem. du Mus. I. (1802). Schrauk, Faun. Boica, 3.
p. 47. Bacillaria Lunula, Schrank, Acta N. Cur. 11. p. 533 (1823). LunuUna vulgaris, Bory, Encyclop. Meth. Hist. Nat. des Zooph. t. 2 (1824).
Turpin, Bid. cFHist. Nat. t. 5. Closteriutn Lunula, Ehr. et Hemprich, Symb. Phys. 1828, t. 2. Ehr. Abh. der
Berl. Ak. 1830; Infus. p. 90. t. 5. f. 15. Kutzmg, Alg. aq. dulc.
No. 22 ; Synopsis Diatom, in Linncea 1833, p. 596. Corda, Aim. de
Carlsbad, 1835, p. 190. t. 5. f. 56 and 57. Jenner, FL of Tunbridge
WeUs, p. 196.
Common. Carnarvon; Dolgelley; Penzance, &c., /. iJ. Several stations in Sussex, Kent, and Surrey, Mr. Jenner. Kerry, Mr. Andrews. Aberdeen- shire, Dr. Dickie and Mr. P. Grant. Near Congleton, Cheshire ; Ambleside, and near Manchester, Mr. Sidebotham.
Germany, Kiitzing, Ehrenberg, Corda. Falaise, Brebisson. Common in New York and New England; Mexico, Bailey.
Frond bright green, stout, distinctly visible to the naked eye, semilunate, five or six times longer than broad ; extremities conic with rounded and very obtuse ends. The upper margin is very convex, the lower straight, except at the extremities which incline upwards, so that the segments rapidly taper from their junction. Endochrome grass-green ; fillets several, three more distinct than the rest ; vesicles numerous, small and scattered.
The empty frond is colourless and without markings, and its suture is indi- stinct or wanting. It shrinks in drying, and is destroyed by burning.
Closteriutn Lunula differs from C. Ehrenbergii and C. moniliferum in having no inflation at the middle of the lower margin ; and although, in drying, it often acquires a prominent centre, its upward inclination at the extremities is a permanent mark of distinction. It may be known from C. acerosum by its stouter appearance and scattered vesicles.
I have never seen a specimen in which the length exceeded the breadth so much as in Ehrenberg's figure.
Meneghini refers C. Lunida of Kutzing's * Alg. Aq. Dul.' to Closterium mo- niliferum ; but two specimens which I have had an opportunity of examining, one in a copy of that publication, and another given me by Kiitzing himself, belong to this species. I have therefore followed Ehrenberg in considering
M
164 BRITISH DESMIDIEiE.
the present as the plant of Nitzsch, whilst the figure m Kiitzing's 'Synopsis Diatomearum' must be referred to C. moniliferum.
Length of frond -^ of an inch ; greatest breadth ■^\^.
Tab. XXVII. fig. 1. a. front ^dew ; b. side view.
2. C. acerosum (Schrank) ; frond linear- lanceolate, gradually tapering ; ends conical ; fillets distinct ; vesicles in a single series ; empty frond colourless; striae none or indistinct.
/3. Frond more elongated ; strite more distinct.
Vibrio acerosus, Schrank, Faun. Boiea, 3. 2. p. 47 (1803).
Clostemim acerosum, Ehrenberg, Abhandl. der Berl. Ahademie (1831) ; Infiis. p. 92. t. 6. f. 1. Meneghini, Synop. JDesmid. in Linncea 1840, p. 233. Kiitzing, Phycoloyia Germanica, p. 131. Jenner, Fl. of Tun- bridge Wells, p. 196. Hassall, British Freshwater Algce, p. 374.
Carnarvon ; Dolgelley ; and Penzance, J. R. Several stations in Sussex, and near Reigate, Surrey, Mr. Jenner. Cheshire and Westmoreland, Mr. Sidebotham. Manchester, Mr. WiUiainson. Aberdeenshire and Banffshire, Mr. P. Grant. Bristol, Mr. Thwaites.
jS. Brackish water at Shirehampton, near Bristol, Mr. Thwaites. Ger- many, Fhrenherg, Kiitzing. Falaise, Brebisson. Mexico, Bailey.
Frond bright green, slender, six to twelve times longer than broad, linear- lanceolate ; ends conical ; lower margin nearly straight, except at the extremi- ties, the conical form of which causes it to incline upwards ; the upper margin slightly convex. Fillets three or more ; vesicles arranged in a single longitu- dinal series.
The empty frond is colourless, and has a transverse line at the suture. This species is generally described as destitute of strise ; but Mr. Jenner and myself have frequently detected them, although seldom distinctly. The striae are more evident in some specimens of /3.
Sporangia have been gathered by Mr. Jenner in Sussex ; they are orbicular, and placed between the deciduous fronds.
Closterium acerosum differs from C Lunula and C lanceolatum in its more slender frond. Some states of it approach nearer to C. turgidum ; it is usually however more slender, and its empty frond also is colourless, and its strise, whenever they occur, are very indistinct.
Length of frond from yJ-g to -^ of axi inch ; greatest breadth from xiws ^^ g-iy ; diameter of sporangium xsr-
Length of variety /3. from A ^^ T2 5 greatest breadth -^.
Tab. XXVII. fig. 2. a. front view of frond with endochrome ; e,f,g. small states ; b, d. empty fronds ; h, i. conjugating fronds ; k, I. perfect sporangia ; m. germinated capsule ? ; e. frond of /3.
3. C. lanceolatum (Kiitz.) ; frond semilanceolate, gradually tapering ; ends subacute ; fillets several ; vesicles in a single series ; empty frond colourless.
Cymbella Hophirldi, Moore, in Harvey's Manual of British Algce, p. 215 (scarcely Conferva ovalis, Hopkirk.) (1841).
BRITISH DESMIDIE.C 163
Chsterium tenue, Bailey, American Journal of Science and Arts, v. 41. p. 303.
t. I. f^7 (1841)? Closferimu lanceolatam, Kiitzing, Phycologia Germanica, p. 130 (1845), in
fit. cum icone. Brebisson, in lit.
About Lisburn ; and near Belfast, Mr. D. Moore. Galway, Mr. M'Calla. Ambleside, Mr. Sidebotham. Westerham, Kent, Mr. Jenner.
West Point, New York, Bailey. Germany, KUtzing. Falaise, Brebisson.
Frond semilanceolate, six to ten times longer than broad ; stouter than that of Closterium acerosmn ; lower margin straight, but inclined upwards at each end owing to the tapering of the extremities ; upper margin convex ; fillets three or more ; vesicles in a single longitudinal series. Empty frond usually colourless and destitute of stride .
Closterium lanceolatum is larger than C. acerosum ; instead of being nearly alike, its margins, as stated above, differ considerably from each other, and its extremities are more tapering. It is distinguished from C. Lunula by having its vesicles in a single series, and its upper margin much less convex. Its ends are neither curved upwards, nor so obtuse as those of C. turgidum.
Length of frond -^ of an inch ; greatest breadth j-i-j •
Tab. XXVIII. fig. 1. a. frond with endochrome ; b. empty frond.
4. C. turgidum (Ehr.) ; lower margin of frond slightly concave, in- clined upwards at the rounded ends ; upper margin with a depres- sion near each extremity ; empty frond coloured ; striae numerous, fine but distinct.
Closterium turgidum, Ehrenberg, lufus. p. 95. t. 6. f. 7 (1838). Meneghini, Synopsis Desmid. in Linncea 1840, p. 234. Jenner, Fl. of Tunbridge Wells, p. 196. Kiitzing, Phycologia Germanica, p. 131. Hassall, British Freshwater Algce, p. 3/1.
Carnarvon ; Dolgelley ; Penzance, /. R. Sussex ; Kent ; Surrey ; Hamp- shire, Mr. Jenner. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Cheshire and Westmoreland, Mr. Sidebotham.
Germany, Ehrenberg . France, Brebisson.
Frond stout, visible to the naked eye, green, six to ten times longer than broad, semilanceolate ; extremities curved upwards, ends broadly rounded. The lower margin is somewhat concave, but always sloped upwards at each end, where the upper margin, which is convex, has a slight depression in consequence of the inclination of the apex upwards. The vesicles form a single longitudinal series ; fillets three or more.
The empty frond is reddish or straw-colour, and somewhat opake ; the suture at the middle is distinct, and so are the longitudinal striae, which are numerous, close and fine.
The curved and rounded ends are characteristic of this species. Closterium decussatum, Kiitz., differs in its more attenuated extremities.
Length of frond -^ of an inch ; greatest breadth 3^ ; distance between the striae ^yW-
Tab. XXVII. fig. 3. a. frond with endochrome ; b. empty fronds.
M 2
166 BRITISH DESMIDIE-E.
ft Frond smooth, crescent-shaped, rapidly tapering from the middle.
5. C. Ehrenbergii (Menegh.) ; frond smooth, crescent- shaped, when empty colourless ; lower margin inflated at the middle ; ends rounded ; vesicles numerous, scattered.
Clostermm Lunida, Ehr. Infus. t. 5. f. xv. 2 (1838). Hassal], Brit. Fresh- water At gee, t. 84. f. 4?
Closterium Ehrenbergii, Meneghini, Synop. Desmid. in Linncea 1840, p. 232. Hassall, Brit. Algae, p. 369 (excl. synonyms), t. 87. f. 1.
Common, often in streams. Henfield, Westham, Tunbridge Wells, &c., Sussex ; Chertsey and Reigate, Surrey, Mr. Jenner. Penzance and Dolgelley, J. R. Bristol, Mr. Thwaites. Ambleside, Westmoreland, Mr. Sidebotham. Aberdeenshire and Banffshire, Mr. P. Grant.
Germany, Ehrenberg . Falaise, Brebisson.
Frond bright green, stout, distinctly visible to the naked eye, lunately curved, five or six times longer than broad, extremities tapering, ends rounded, lower margin very concave with an inflation at the middle ; fillets several, three of them more evident ; vesicles numerous, small and scattered. Empty frond colourless, without a suture at the middle, collapsing when dried.
Closterium Ehrenbergii agrees with C. Lunula and C. moniliferum in size, colour and texture : it is more curved than the former, the lower margin being concave, not straight, and its centre is protuberant. From the latter it differs in its vesicles, which are smaller, more numerous and scattered.
Length of frond -gL of an inch ; greatest breadth -j^-^.
Tab. XXVIII. fig. 2. frond with endochrome.
6. C. moniliferum (Bory) ; frond smooth, crescent-shaped, when empty colourless; lower margin inflated at the middle; ends rounded; vesicles in a single row.
Lunulina monilifera, Bory, Encycl. Method. Hist. N. des Zooph. 1824, t. 3. f 22, 25 and 27.
Closterium Lunula, var., Ehr. Abh. der Berl. Ak. 1830, p. 62.
Closterium acerosum, var., Ehr. Abh. der Berl. Ak. 1831, p. 68.
Closterium Lunula, Kiitzing, Sgnop. Desmid. in Linncea 1833, f. 80. Bre- bisson, Alg. Fal. p. 58. t. 8.
Closterium moniliferum, Ehr. Infus. p. 90. t. 5. f. 16 (1838). Meneghini, Synop. Desmid. in Linncea 1840, p. 232. BaWey, Amer. Bacil.in Amer. Journ. of Science and Arts, v. 41. p. 302. t. 1. f. 31. Jenner, Ft. of Tunbridge Wells, p. 196. Kiitzing, Fhy. Germ. p. 130. Hassall, Brit. Alg. p. 370.
Common. Penzance and Dolgelley, J. R. Framfield and Hastings, Sussex ; and Beigate, Surrey, Mr. Jenner. Kerry, Mr. Andrews. Cheshunt, Mr. Hassall. Near Bristol, Mr. Thwaites. Yate, near Bristol, Mr. Broome. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Banifshire, Mr. P. Grant. Cheshire and Westmoreland, Mr. Sidebotham. Manchester, Mr. JVilliamson.
Germany, Ehrenberg, Kiitzing, Corda, &c. Falaise, Brebisson. Common in New York and New England, Bailey.
BRITISH DESMIDIE^.. 16?
Frond bright green, stout, distinctly visible to the naked eye. Innately curved, five or six times longer than broad, extremities tapering, ends rounded ; lower margin very concave, inflated at the middle ; fillets several, one to three more distinct than the rest ; vesicles few, large, and disposed in a single longitudinal series. The empty frond, colourless and vrithout a suture at the middle, col- lapsing w^hen dried.
Closterium monilifermn is smaller than C. Lunula and more curved, and it
may ahvays be distinguished by the inflation at the middle of its lower margin ;
its vesicles form a single series, a character which separates it also from
C Ehrenbergii.
Length of frond from ^^ to ^ of an inch ; greatest breadth from 3^^^ to 1
Tab. XXVIII. fig. 3. a. frond with endochrome ; b. empty frond.
7. C. Jenneri ; frond crescent-shaped, generally slightly con- stricted at the suture, when empty colourless, rapidly tapering; ends very obtuse ; vesicles in a single series.
Closterium moniliferum, Ehr. Infus.t, 5. f. 16. n. 6, 7 (1838). Sussex ; Surrey ; and Hampshire, Mr. Jenner. Penzance, J. R.
Frond smaller than that of Closterium moniliferum, much curved ; extre- mities tapering ; ends rounded. There is generally a slight constriction at the suture. Fillets two or three. The empty frond colourless and without markmgs.
Closterium Jenneri is more curved than C. moniliferum, and there is no inflation of its lower margin. It is more curved than C. Leibleinii and C jyiance, and its ends are far more obtuse than theirs.
Length between ends of frond -^^ of an inch ; breadth at suture -yttq-
Tab. XXVIII. fig. 6. a, b. fronds with endochrome ; c. empty frond.
8. C. Leibleinii (Kiitz.) ; frond smooth, crescent-shaped ; extremities much attenuated and subacute at the apex ; lower margin slightly inflated at the middle ; vesicles in a single row.
/3. More slender, the central inflation less evident ; empty frond of a deeper colour and its central suture distinct.
Closterium Lunula, Leibl. Fl. 1827, p. 259. according to Kilts;.
Closterium Leibleinii, Kiitzing, Synop. Diatom, in Linncea 1833, p. 596 ;
Phrjcol. Germ, p. 130. Brebisson, Alg. Fal. p. 58. t. 8. Meneghini,
Synop. Desmid. m Linncsa 1840, p. 232.
Cheshire, Mr. Sidebotham. Albourn, Framfield, and Hastings, Sussex ; and Reigate, Surrey, Mr. Jenner. Penzance and Dolgelley, J. R. Rochdale, Mr. Coates. Aberdeen, Mr. P. Grant. Shirehampton near Bristol, Mr. Thwaites.
Germany, Kiitzing. Falaise, Brebisson.
Frond small, crescent-shaped, stout, about four to eight times as long as
168 BRITISH DESMIDIEiE.
broad; extremities tapering to a subacute apex. At the centre of the lower margin is a slight protuberance, which however is often nearly obsolete. Fillets frequently obscure ; vesicles few, large, and disposed in a single series. The empty frond has generally a pale straw-colour tinge, and a transverse suture is usually visible at the centre.
Clostermm Leibleinii much resembles a young specimen of C. moniliferum ; but it is smaller and more curved, the ends are more acute, and the empty frond is usually coloured.
The variety /3. is nearly intermediate between this and the following species.
I have gathered the sporangia at Penzance and Dolgelley ; Mr. Jenner has found them in Sussex, and Mr. Thwaites near Bristol. They are orbicular, and but loosely connected with the empty segments of the fronds.
Length of frond from -jiy to -^^ of an inch ; greatest breadth from xsVa to 5^^ ; length of sporangium from y^Vo ^^ "ozr '■> breadth from 2^75" ^^ T2Ts-
Tab. XXVIII. fig. 4. a, c,f, i, h. different states of frond with endochrome ; b, d, e. empty fronds ; ff, h, I. sporangia.
9. C. Diana (Ehr,) ; fronds smooth, slender-crescent-shaped ; extre- mities tapering ; apex subacute ; lower margin not inflated ; vesicles in a single series.
Closterium ruficeps, Ehr. Abh. der Berl. Ak. 1831, p. 67. Closteriiim Biance, Ehr. Lifus. p. 92. t. .5. f. 17 (1838). Kiitzing, Phy. Germ. p. 130. Hassall, Brit. Freshwater Alg. p. 371.
Sussex, Mr. Jenner. Dolgelley, J. R. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Cheshire and Ambleside, Mr. Sidebotham.
Germany, Ehrenberg . Falaise, Brebisson.
Frond slender, six to eight times longer than broad, curved ; extremities tapering to a subacute point. The lower margin is concave and not inflated at the centre. Fillets obscure ; vesicles disposed in a single longitudinal series.
The empty frond has a pale straw-colour tint, and a transverse suture at the centre, where, as in C. Leibleinii, the segments easily separate.
This plant differs from C Leibleinii in being longer, more slender and less curved, and in having no projection at the centre of the lower margin ; yet I have doubts whether they are really distinct, as I have seen some specimens apparently intermediate.
Length between ends of frond yij of an inch ; greatest breadth yaVs"-
Tab. XXVIII. fig. 5. a, b. fronds with endochrome ; c. empty frond.
ttt Frond nearly straight, scarcely attenuated ; ends truncate ; longi- tudinal stria none or indistinct.
10. C. didymotocum (Corda) ; frond nearly straight, broadly linear ; extremities slightly tapering ; ends truncate, reddish ; fillets ob- scure.
BRITISH DESMIDIE^. 169
a. Empty frond divided into four portions by three transverse lines or sutures.
Clostermm didymotocxim, Corda, Almanack de Carlsbad, 1835, p. 125. t. 5.
f. 64, 65. Brebissow, in lit. cum icone et specimine. Closterium subrectum, Brebisson, Alg. Fal. p. 59. t. 8 (1835), Kiitzing,
Phijcoloyia Germanica, p. 131.
/3. Baillyanum (Breb.) ; frond smaller with a suture only at the
middle.
Closterium Baillyanum, Brebisson, in lit. cum icone et specimine (1845).
a. Rare. Dolgelley, J. R.
/3. Common. Dolgelley and Penzance, J. R. Sussex ; Surrey ; and Hampshire, 3Ir. Jenner. Aberdeenshire, Mr. P. Grant. Ambleside, Mr. Sidebotham.
Germany, Corda, Kiitzing. a. et /3. Falaise, Brebisson.
Frond six to ten times longer than broad, stout, nearly straight, equal ex- cept at the extremities, which taper more or less ; ends truncate, fillets obscure ; vesicles in a single longitudinal series ; terminal globules and moving granules distinct.
Empty frond reddish, especially at the ends, where the colour is conspi- cuous even before the endochrome has collapsed. Faint striae may generally be detected in old specimens.
The variety fl. is by M. de Brebisson considered a distinct species. The only chfference I can discover is in the number of sutures, and I doubt whether any dependence can be placed on this character. Closterium Baillyanum is also usually smaller than a, but not invariably, and before the escape of the endochrome I am unable to distinguish them even as varieties.
Closterium didymotocum may be known from all the preceding species by its straight frond combined with trmicate ends. It differs from C. striolatum, C. intermedium, and C. angustatum, in the absence or indistinctness of its striae and the upward inclination of the lower margin at the extremities.
Length of frond m /3. -^ of an inch ; breadth -g\^.
Tab. XXVIII. fig. 7. a. frond of a. with endochrome; b. empty frond; c. frond of j8. with endochrome ; d. empty frond.
tttt Empty frond distinctly striated, mostly coloured.
11. C. attenuatum (Ehr.) ; frond curvedj attenuated, suddenly con- tracted at the end into a conical point ; empty frond reddish, faintly striated.
Closterium attenuatum, Ehrenberg, Tnfusor. p. 94. t. 6. f. 4 (1838). Kiitzing, Phycologia Germanica, p. 131. Brebisson, in lit. cum icone. Chiltington Common near Pulborough ; Midhurst ; Ashdown Forest ; near Tmihridge AVells, &c., Sussex ; Reigate, Surrey, Mr. Jenner. Dolgelley and Penzance, /. R. Ambleside, Mr. Sidebotham.
Berlin, Ehrenberg . Falaise, Brebisson. . Frond rather larger than that of Closterium striolatum, eight to twelve
170 BRITISH DESMIDIE^.
times longer than broad, curved, gradually attenuated, and at the end suddenly contracted into an obtuse, conical or subcylindrical point. Fillets obscure ; vesicles in a single longitudinal series. Empty frond reddish, especially at the end?, transverse suture distinct. Longitudinal strise numerous, close, gene- rally faint, but sometimes very distinct.
Closterium attenuatum might be supposed an incomplete state of another species, especially when its ends are dissimilar ; but the sudden contraction of the extremities is a sufficient distinction.
Length of frond -^ of an uich ; greatest breadth -^ ; distance between the
stnae 2631 s*
Tab. XXIX. fig. 5. a. frond with endochrome ; h. empty frond.
12, C. cosfatum (Corda) ; frond stout, semilunate or crescent-shaped, tapering from the middle ; ends obtuse ; striae few and conspicuous ; suture solitary.
Closterium costatum, Corda, Almanach de Carlsbad, 1835, p. 124. t. 5. f. 61 to 63 ; Observations microscopiques sur les Animalcules desEaux et des Thermes de Carlsbad, p. 34. Brebisson, in lit. cum icone.
Closterium doliolatum, Brebisson, Meneghini, Synopsis Besmid. in Linncea 1840, p. 237.
Closterium dilatatum, Kiitzing, Phycologia Germanica, p. 132 (1845) ; in lit. cum icone.
Dolgelley ; and Penzance, /. R. Sussex ; Surrey ; and Hampshire, Mr. Jenner. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Ambleside, Mr. Sidebotham. Near Bristol, Mr. Broome.
Carlsbad ; and Prague, Corda. Falaise, Brebisson.
Frond stout, five or six times longer than broad, crescent-shaped or nearly semilunate, rapidly attenuated from the centre ; end obtuse or somewhat trun- cate. Fillets obscure ; vesicles in a single series.
The empty frond is reddish, with a single transverse sutiAe generally of two or more lines. The longitudinal strise, which are few compared to the breadth of the frond, are so very distinct that they may be counted without difficulty.
I have gathered a single sporangium at Dolgelley ; it was orbicular, and resembled that of Closterium striolatum.
This species agrees with Closterium angustatum in its distinct, subdistant strise ; but their forms are widely different. It is stouter in proportion to its length than either C. turgidum or C. striolatum, and its strise are much fewer than theirs.
Length of frond -^-^ of an inch ; greatest breadth -^^^ ; distance of strise apart -j^.
Tab. XXIX. fig. I. a. frond with endochrome; b. empty frond.
13. C. striolatum (Ehr.) ; frond closely but distinctly striated, semi- lunate or crescent-shaped, tapering from the middle ; sutures gene- rally three, never more.
Closterium striolatum, Ehrenberg, Abh. der Berlin. Ah. 1833, p. 68 ; Infusor.
BRITISH DESMIDIE.E. I7I
p. 95. t. 6. f. 12. Meneghini, Spiopsis Desmid: inLinnaiu 1840, p. 234. Bailey, Amer. Journ. of Science and Arts, v. 41. p. 303. t. 1. f. 35. Kiitzing, Phycologia Gennanica, p. 131. Jenner, Fl. of Tunbridye JJ'elis, p. 196. Ilassall, Brit. Freshwater Algce, p. 3/3.
Common. Carnarvon ; Dolgelley ; Tal Sam near Lampeter ; near Car- marthen ; and Penzance, /. R. Sussex ; Surrey ; Kent ; and Hampshire, Mr. Jenner. Kerry, Mr. Andrews. Galway, Mr. M'Calla. Hertfordshire, Mr. Hassall. Aberdeenshire, Dr. Dickie and 3Ir. P. Grant. Cheshire and Westmoreland, Mr. Sidebotham. Manchester, Mr. Gray and Mr. Wil- lianiso?i.
Germany, Ehrenberg. New York ; and New England, Bailey. Falaise, Brebisson.
Frond six to twelve times longer than broad, very variable in both length and breadth, curv^ed, tapering from the middle ; ends very obtuse ; upper margin convex ; lower concave or straight, but never inclined upwards at the ends. Vesicles in a single series ; fillets often obscure. This species forms yellomsh-brown masses in the water.
The empty frond is reddish and darkest at the ends. Striae numerous, crowded, and easily detected. Sutures usually three, but sometimes only two : specimens with a single suture are very rare.
The sporangia, which are not macommonly met with, are orbicular and placed between the deciduous fronds.
Closterium striolatum is shorter than C. turgidum, and the ends do not turn up ; its striae are much more numerous and close than those of C. costatum ; and both C. turgiduni and C. costatum have constantly but a single suture. It is more closely striated than either C. intermedium or C. angustatum, and stouter also in proportion to its length. With this species C. didymotocum in some respects agrees as to its size and form, but it is straighter and less tapering, and its ends are more truncate, and the strise, if present, are detected with the greatest difficulty.
Length of frond from ^^ to ^L of an inch ; greatest breadth from -g-L- to •g-L ; distance between the strise y^.oTo.
Tab. XXIX. fig. 2. a,b, c. fronds with eudochrome ; d, e,f. empty fronds ; g, h. sporangia.
14. C. intermedium ; frond slender, slightly curved, tapering ;
striae distinct, not crowded ; sutures usually more than three. Dolgelley, J. R.
Frond slender, nearly straight, many times longer than broad, very gradu- ally tapering, ends truncate. Fillets obscure ; vesicles in a single series. This species forms in the water large masses of a yellow-brown colour.
The empty frond is straw-colour ; its strise are distinct and can be counted without difficulty. Sutures, though occasionally but three, are usually from four to seven in number. The central suture often forms a pellucid line re- sembling a dissepiment.
In its form and in the number of its striee Closterium intermedium is inter- mediate between C. striolatum and C. angustatum. According to M. de Bre- bisson, 6'. striolatum has about forty strise, C. intermedium twenty, and C. an-
172 BRITISH DESMIDIE^.
gustatum, ten or twelve. The most remarkable feature In this plant is the number of its sutures exceeding that of any other species ; it is more slender and tapers more gradually than C. striolatum. Its more numerous striae and tapering form distinguish it from C. angustatum.
Length of frond from y^ to -^ of an inch ; greatest breadth ^^^ 3 ; distance between the striae ytstt-
Tab. XXIX. fig. 3. a. frond with endochrome ; b, c. empty fronds.
15. C. angustatum (Kiitz.) ; frond sublinear, curved, scarcely attenu- ated ; ends truncate ; striae few, very distinct and prominent ; sutures usually three.
Closterium angustatum, Kvitzing, Phycologia Germanica, p. 132 (1845) ; in
lit. cum icone. Closterium sulcatum, Brebisson, in lit. cum icone (1845).
Dolgelley, /. R. Waterdown Forest, &c., Sussex ; Reigate, Surrey, Mr. Jenner. Aberdeenshire, Mr. P. Grant. Ambleside, Mr. Sidebotham.
Germany, Kutzing. Falaise, Brebisson.
Frond curved, eight or more times longer than broad, nearly equal in breadth except towards the extremities which are somewhat attenuated, their ends however being truncate. The vesicles are arranged in a single longitu- dhial series ; fillets obscure.
The empty frond is of a pale reddish colour and darkest at the ends. Trans- verse sutures usually three, the central one of two or more lines. The longitu- dinal striae, of which seldom more than three or four can be seen at one view, are few in number, very distinct and prominent, and not unfrequently some- what spiral. The frond, I believe, has several angles or ridges, which under the glass have the effect of striae.
Its linear form and scarcely attenuated extremities distinguish this species from Closterium intermedium. The striae also are fewer in number, less crowded, and more distinct. C. angustatum differs from C.juncidum by its stouter form and more distinct striae ; its vipper margin also is convex, and not straight as in that species.
Length of frond -^ of an inch ; greatest breadth Y1V2 5 distance between the striae y^.
Tab. XXIX. fig. 4. a. frond with endochrome ; b, c. empty fronds.
16. C. juncidum ; frond elongated, very slender, linear, straight
except at the extremities, which are slightly attenuated and curved downwards.
/3. Frond stouter and less elongated.
a. Dolgelley and Penzance, J. R. Chiltmgton Common near Pulborough, Sussex, Mr. Jenner. Aberdeenshire, Dr. Dickie and Mr. P. Grant. Amble- side, "Westmoreland ; and Congleton, Cheshire, Mr. Sidebotham.
/3. Dolgelley, J. R. Midhurst, Sussex, Mr. Jenner. Falaise, Brebisson.
Frond many times longer than broad, ^ery slender, linear, straight except
BRITISH DESMIDIEJE. l73
at the extremities, which are shghtly attenuated and curved downwards ; ends obtuse. Fillets and vesicles none or obscure.
In a. the empty frond is nearly colourless, and the longitudinal striae are faint. In [i. the colour is deeper and the striae more conspicuous. Trans- verse sutures usually three.
I have gathered sporangia at Dolgelley and Penzance ; they are orbicular and placed between the deciduous fronds.
The slender linear frond distinguishes this species.
Length of frond from ytt ^^ T9 ^^ ^^ ^^^^ 5 breadth ^oW J diameter of sporangium -^^ ; distance between the striae xoo-q-o .
Length of fi. ^j^- ; breadth -g^jo ; length of sporangium -^^r > breadth -^ig- ; breadth between the striae yttjt'
Tab. XXIX. fig. 6. a. frond of a. vrith endochrome ; b. empty frond ; c, d. sporangia. Fig. 7. a. frond of /3. with endochrome ; b. empty frond ; c, d. sporangia,
** Frond striated^ much elongated, gradually tapering, scarcely ros- trate ; sporangium bilobed, situated betiveen the conjugated fronds. 17. C. lineatum (Ehr.); frond striated, slender, long, curved, gradu- ally tapering into the conico-rostrate extremities; lower margin slightly inflated at its centre. /3. Longitudinal striae spiral.
Clostei'ium lineatum, Ehrenberg, Abhandl. der Berlin. Akademie 1833, p. 238 ; Infusor. p. 95. t. 6. f. 8. Meneghini, Synop. Desmid. in LinncBa 1840, p. 234. Kiitzing, Phycologia Germanica, p. 131. Jenner, Fl. of Tun- bridge Wells, p. 196. Hassall, British Freshwater Algce, p. 372.
Closterium elongatiun, Brebisson, Meneghini, Synopsis Desmid. p. 234 (1840).
Carnarvon ; Dolgelley ; and Penzance, J. R. Ashdown Forest, and Water- down Forest, Sussex, Mr. Jenner. Aberdeenshire ; and Banifshire, 3Ir. P. Grant. Manchester, Mr. Sidebotham.
Germany, Ehrenberg, Kiitzing. Falaise, Brebisson. Mexico, Bailey.
Frond large, twelve or more times longer than broad, slightly curved, lan- ceolate, gradually tapering into the slender extremities, which are curved down- wards and obtuse at the end. The upper margin is slightly but uninterrupt- edly convex, so as to form an arc ; the lower margin is concave, owing to the curved extremities, but it is slightly protuberant at the centre. Endochrome reaching nearly to the ends ; fillets three or more, frequently obscure ; vesi- cles in a single longitudinal series.
Empty frond of a pale straw-colour, with numerous but distmct longitudinal striae, and one or more transverse hues at the centre. Specimens occasionally are met with having the striae spirally arranged. This state, which is very beautiful, I can only regard as an accidental variety, as I have observed such a frond conjugated with one of the common kind.
Closterium lineatum connects the rostrate vdth the other striated species, as in general aspect it agrees with some of the latter, and in its inflated centre and tapering extremities vdth the former. It is liable to be mistaken for C. Ralfsii, but it is longer, more slender, less inflated at the centre, and more
174 BRITISH OESMIDIEAi.
gradually attenuated ; the colour too of its empty frond is paler, and its striae are not quite so crowded.
I have frequently gathered the sporangium near Dolgelley, and Mr. Jenner has gathered it in Sussex. It is very remarkable, being the only known ex- ample of a geminate or bilobed sporangium. The fronds approach and couple in the usual manner ; but instead of the contents of both fronds uniting in the ordinary manner into a single body, a bilobed body is produced not unlike a species of Cosmarium in form. A distinct line is perceptible between the lobes or portions, and each resembles a globular or oval body flattened at the junc- tion, and is formed by the contents of the adjacent segments. The sporan- gium is more closely comiected with the conjugated fronds than is the case in species belonging to the first section, but the fronds are not permanently united to it as in Closterium rostratum. Although I have here called it bilobed, I regard the sporangium as binate, rather than bilobed, because it readily sepa- rates at the junction, each portion retaining the segments of the frond belong- ing to it.
Length of frond ■— of an inch ; greatest breadth -^\^ ; length of the bilobed sporangium ^^-3 ; greatest breadth -3^^^ ; distance between the striae ■2WZT5'
Tab. XXX. fig. 1. a. frond with endochrome; b. empty frond; c. sporan- gium.
*** Frond either rostrate or minute, colourless and acicular ; sporan- gium cruciform. (Stauroceras, Kutz.)
t Frond striated, tapering at each end into a distinct beak.
18. C. Ralfsii (Breb.) ; frond stout, striated, curved, rapidly attenuated into linear beaks which are shorter than the ventricose body.
Closterium rostratum, Ralfs, in Jenner, Fl. of Tunhridge Wells, p. 196 (1845)
(not of Ehrenberg according to Brebisson) . Closterium Ralfsii, Brebisson, in lit. (1845). Stauroceras Ralfsii, Brebisson, in lit. (1846).
Carnarvon and Dolgelley, J. R. Midhurst ; near Tunhridge Wells, &c.,. Mr. Jenner. Aberdeenshire, jDr.Dte^ie. Near Manchester ; and Ambleside, Mr. Sidebotham.
Falaise, Brebisson.
Frond yellowish-browii, stout, six to eight times longer than broad ; the upper margin convex, the lower concave, but ventricose at the centre ; extre- mities tapering into a narrow linear beak, which is curved downwards, shorter than the body, and obtuse at the apex. Vesicles disposed rather irregularly in a single longitudinal series. Fillets generally obscure.
The empty frond, which is firm, is reddish, especially at the ends. Striae numerous, close, and distinct ; transverse suture solitary.
This and the two following plants differ considerably from the other striated species {Closterium lineatum. in some respects excepted). The body of the frond is somewhat lanceolate, being equally convex on both margins, and tapering at each end into a linear or setaceous beak, which is curved down-
BRITISH DESMIDIEiE. 1 7$
ward and thus gives the frond a curved appearance. The green endochrome is nearly confined to the inflated body.
Closteriiim Ralfsii may be known from C. rostratiim and C. setaceum by its larger size, the deeper colour of its empty frond, the shortness of its beaks, its firmer texture, and by the upper margin, which, inclusive of the beaks, forms an uninterrupted convexity or arc.
Length of frond yL of an inch ; greatest breadth g-i^ ; distance between the striae ^rm-
Tab. XXX. fig. 2. a. frond with endochrome ; b. empty frond.
19. C. rostratum (Ehr.) ; frond striated, tapering at each end into a setaceous curved beak which is about equal in length to the ventri- cose body ; sporangium cruciform.
Closteriiim rostratum, Ehrenberg, Abhandl. der Akademie d. Wissensch. zu
Berlin 1831, p. 67 ; 1833, p. 2 10 ; hifus. p. 97. t. 6. f. 10. Meneghini,
Synop. Desmid. in Linncea 1840, p. 235. Closterium Acns, Nitzsch, Kiitzing, Synopsis Biatomearum in Linncea 1833,
p. 595. f. 81 ; Alg. aq. dulc. No. 80. Jenner, Fl. ofTunbridge Wells,
p. 196. Closterium cmidatum, Corda, Almanack de Carlsbad 183^, p. 125. t. 5. f. 66. Stauroceras Acus, Kiitzing, Phycologia Germanica, p. 133(1845). Brebisson,
in lit. cum specimine.
Dolgelley and Penzance, J. B. Sussex ; Kent, 3Ir. Jenner. Durdham Down near Bristol, Mr. Thwaites. Near Congleton, Cheshire ; Ambleside, Westmoreland ; and near Manchester, Mr. Sidebotham. iVberdeenshire, Mr. P. Grant.
Germany, Ehrenberg, Kutsing, Corda. Falaise, Brebisson.
Frond lanceolate, tapering into setaceous beaks, which are curved downiwards at the extremity, obtuse at the apex, and nearly equal in length to the inflated body.
Endochrome green, confined to the inflated portion ; fillets obscure ; vesicles arranged in a single series ; the moving granules are situated at the end of the endochrome, and apparently are not contained within a globule, as their mo- tion has a wider range than in many other species.
The empty frond is colourless or tinged straw-colour, and the striae are numerous and close.
Mr. Jenner and myself have gathered conjugated specimens of Closterium rostratum in greater abundance than those of any other species. The cell formed for the reception of the sporangium is intimately connected with the fronds, of which indeed it seems to form a part. When viewed in front it may be described as a four-sided figure, whose angles are cut off at their union with the segments. All its sides are concave, but those between the segments of the same frond are shorter than the others and have deeper and more angular concavities, so that the sporangium has the same figure as the cell.
Length of frond -^ of an inch ; greatest breadth yoW 5 length of sporan- gium y^j^ ; breadth 3^5^ ; distance between the striae ^sooo-
Tab. XXX. fig. 3. a. frond with endochrome ; b, d. empty fronds ; c. conju- gated fronds ; e. sporangium.
1^6 RRITISH DESMIDIE^.
20. C. setaceum (Ehr.) ; frond very slender, finely striated, narrow- lanceolate, tapering at each extremity into a very long setaceous beak, which alone is curved ; vesicles none or obscure.
Closferium setaceum, Ehrenberg, Abhandl. der Berlin. Ak. 1833, p. 239 ; Infiis. p. 97. t. 6. f. 11. Meneghini, Synop. Desmid. p. 235. Jenner, Fl. of Tunbridge Wells, p. 1 96. Hassall, Brit. Freshwater Algce, p. 373.
Closte?-ium rostratum, Bailey, Amer. Bacillaria in Amer. Joiirn. of Science and Arts, v. 41. p. 303. t. 1. f. 36 (1841).
Staui'oceras subulatum, Kiitziiig, Phycologia Germanica, p. 133 (1845).
Stauroceras setaceum, Brebisson, in lit. (1846).
Dolgelley, J. R. Waterdown Forest ; and near Cross-in-hand, Sussex, 3Ir. Jenner. Near Bristol, 3Ir. Broome. Near Aberdeen, Mr. P. Grant.
Germany, Ehrenberg . Staten Island, New York, Bailey. Falaise, Bre- bisson.
Frond minute, many times longer than broad, very slender ; the body nar- row-lanceolate, straight, attenuated at each end into a setaceous beak or awn, which is longer than the inflated portion, curved downwards at the extremity and blunt at the apex. The endochrome is pale, and does not extend beyond the inflated part. Vesicles none or indistinct ; fillets none ; moving granules not contained within a globule.
The empty frond is colourless, and exhibits close and famt striae.
Conjugated specimens are not uncommon. The process differs but little from that described under the preceding species. The sporangium in this species also appears like a continuation of the segments, and is quadrate or cruciform.
Closterium setaceum may be known from C. rostratum and C. gracile by its slender beaks being longer than the body of the frond.
Length of frond -^j-^ of an inch ; greatest breadth ^3^3^ ; distance between the striae xyoT-
Tab. XXX. fig. 4. a. frond with endochrome ; b. empty frond; c. sporangium.
tt Frond minute, tapering, not rostrate ; empty frond colourless and
without markings.
21. C. CorwM (Ehr.); frond smooth, minute, curved, very slender; extremities slightly attenuated ; ends obtuse ; vesicles none or indistinct.
/3. Frond more turgid.
Closterium Cornu, Ehrenberg, Abhandl. der Berlin. Ak. p. 62 (1830) ; Infusor. p. 94. t. 6. f. 5. Meneghini, Synop. Desmid. in Linncea 1840, p. 233. Jenner, Fl. of Tunbridge Wells, p. 196. Kiitzing, Phycologia Germa- nica, p. 131. Hassall, Brit. Freshwater Algce, p. 372.
Closterium. tenue, Kiitzing, Synopsis Diatom. inLinncea 1833, p. 595. f. 78 ; Phycologia Germanica, p. 130.
Henfield, Piltdown Common, Battle, and Rackham Bogs, Sussex, Mr. Jenner. Dolgelley, J. R. Ambleside, Mr. Sidebotham.
Germany, Ehrenberg, Kiitzing. Falaise, Brebisson.
BRITISH DESMIDTE.E. 177
Frond very minute, five to eight times longer than broad, slender, slightly curved ; extremities attenuated ; ends blunt, but frequently one more so than the other. The figure of the frond is variable ; the upper margin is more or less convex, the lower one concave or straight ; occasionally the extremities curve in opposite directions. Endochrome very pale. Vesicles wanting ac- cording to jMcneghini ; but INIr, Jeimer informs me that they are present, although indistinct. The empty frond is colourless.
]\Ir. Jenner has gathei'ed conjugated specimens at Rackham Bogs. The sporangium, which is quadrate, is large compared with the size of the plant. The empty segments of the frond remain attached to the angles of the spo- rangium.
Closterium Cormi differs from C. acutum in its obtuse ends.
Length of frond -^^ of an inch ; breadth -j^Vg •
Length of (j. ^4^ ; breadth a^O" '■> length of sporangium -^\^ to -^\^ ; breadth -pfL_ to ^.
Tab. XXX. fig. 6. a, b. fronds of /3. with endochrome ; e, d. front views of sporangia ; e. side view of sporangium \ f, y. fronds of a.
22. C acutum (Lyngbye) ; frond curved, gradually tapering at each extremity ; end more or less acute ; empty frond colourless.
a. Frond six to twelve times longer than broad ; ends subacute.
EchineJla acuta, Lyngbye, Tent. Ilydrophytologice Danicce, p. 209. t. G9. G.
(1819). Frustulia acuta, KUtzing, Synopsis Diatomearum in Linncea 1833, p. 537. Closterium acutum, Brebisson, in lit. cum icone (1845). Stauroceras acutum, Brebisson, in lit. (184G).
/3. Frond ten to twenty times longer than broad, tapering at each
extremity into a very fine point.
Frustulia subidata, Kutzing, Synop. Diatom, p. 538. f. 3 (1833). Stauroceras subulatum, Brebisson, in lit. cumicone (1846).
Dolgelley and Penzance, J. R. Rochdale, 3Ir. Coates. Brightling near Battle, Sussex, Mr. Jenner.
Germany, KUtzing. Falaise, Brebisson.
Frond very minute and slender, many times longer than broad, narrow-lan- ceolate or acicular, slightly curved, gradually tapering ; extremities hyaline, and more or less acute at the apex. Vesicles obscure ; fillets none ; endo- chrome \ery pale, and not extending to the extremities. The moving granules are free, and more or less remote from the ends.
The empty frond is quite colourless and free from markings.
Sporangia are not uncommon. I have frequently gathered them at Dol- gelley and Penzance, and M. de Brebisson has sent me drawings of French specimens. The sporangium is cruciform in the front and oval in the side view. It is inclosed in a cell, similar to itself in form, but extending beyond it at the angles into the adjoining portion of the respective segments. In their empty state the segments have so much the colour and appearance of the water in which they are immersed that it is diflScult to trace them, and the
J78 BRITISH DESMIDIE.E.
portions of the cell which project into the segments may be mistaken for them. The same circumstance renders it difficult to determine the exact form of the attenuated ends.
By Brebisson Closterium suhulatnm is regarded as a distinct species ; and no doubt extreme states differ considerably, but I am unable to detect any di- stinctive character on which I can rely.
Closterium aciitum differs from C. Cornu in its tapering frond and acute ends ; its fronds are also far more closely united with the sporangium.
Length of frond y|-^ of an inch ; greatest breadth i^j-g-^ ; length of sporan- gium TiVr to -^ ; breadth -^^.
Tab. XXX. fig. 5. a, b. fronds of a ; c. frond of /3 ; d. conjugated fronds from a drawing by Brebisson ; e. front view of sporangium ; f. side view of sporangium from a drawing by Brebisson. Tab. XXXIV. fig. 5. sporangium.
17. SPIROT.ENIA, 5r^*.
Frond simple, elongated, cylindrical or fusiform, straight, entire, not constricted at the middle ; ends rounded ; endochrome spiral.
The fronds are simple, straight, cylindrical, slightly attenuated at the extremities ; they are quite entire and not constricted at the mid- dle. The endochrome is spiral, as in Zygnema, and, except in fronds about to divide, there is no interruption at the centre.
The spiral arrangement of the endochrome will distinguish SpirO' tania from every other genus in the family. It also differs from Tet- memorus in the entire extremities, and from that genus as well as from Docidiiim in the absence of a constriction at the centre. It dif- fers likewise from Closterium by its straight fronds and the absence of a globule near the extremities.
Spirotania affords another example of resemblance to the Conju- gatJE. The endochrome is so exactly like that of Zygnema, that, until we saw M. de Brebisson's drawing, both Mr. Jenner and myself had regarded the S. condensata as the young state of a Zygnemu. It however does not form a filament, the cells dividing in the manner of the Desmidieae ; but the division is oblique, as in Scenedesmus ; thus affording a character by which it may be distinguished from Penium, even should the spiral form of the endochrome be absent.
In Spiroicenia the complete division of the cell is prior to the divi- sion of the gelatinous covering, which thus retains the two newly parted cells together for some time longer; a fact which convincingly proves that this genus belongs to the Desmidieae.
BRITISH DESMIDIEi^E. 1 79
1. S. condensata (Breb.) ; endochrome a single, broad, closely spiral band.
SpirotcB)iia condensata, Brebisson, in lit. cum icone (1846).
Common. Dolgelley and Penzance, J. R. Henfield, Sussex, and bogs at Fisher's Castle, Tuubridge Wells, 3Ir. Jenner. Ayrshire, Rev. D. Lands- horough. Aberdeenshire, Hr. Dickie and Mr. P. Grant. Ambleside, Mr. Sidebotham. Near Bristol, Mr. Thwaites.
Falaise, Brebisson.
Frond bright yellow-green, cylindrical with rounded ends, or fusiform, five to ten times longer than broad, enclosed in an evident mucous covering. The endochrome consists of a single broad spiral band. The revolutions are close, and from seven to twelve in number.
This is a beautiful plant ; and in a recent state the spiral arrangement of the endochrome is very conspicuous, but it collapses shortly after being gathered.
Length of frond yi-g- of an inch ; breadth y^xs •
Tab. XXXIV. fig. 1 . a, b. mature frond ; c. fronds after division.
2. S. obscura ; endochrome at first in several slender spiral
threads, afterwards uniform.
Dolgelley and Penzance, J. R. Bogs at Fisher's Castle, Tunbridge "Wells, Mr. Jenner.
Frond dark green, cylindrical or fusiform, extremities attenuated, five to eight times longer than broad. When young the endochrome is distinctly spiral, and the frond resembles a joint of a many-spired species of Zygnema. The threads or fillets are several in number, slender, and each of them makes but one or two revolutions in the length of the frond. Generally however the endochrome forms a uniform dark green mass without any appearance ot spires. In this state, a small hyaline space left at each extremity will fre- quently be found to contain a small granule.
I long regarded this species as probably a variety of Spirotcenia condensata, nor was it until I met with a young specimen that I was fully satisfied of its distinctness. Even specimens which do not exhibit the spires may be recog- nized by the darker colour of their endochrome and more tapering extremities.
Length of frond from ^\j to -j-i-g- of an inch ; greatest breadth from -^-^
to
907 •
Tab. XXXIV. fig. 2. a,b,c. single fronds ; d, e. fronds after division.
*** Cells fasciculated. 18. ANKISTRODESMUS, Corda. Cells elongated, attenuated, entire, aggregated in faggot-like bundles. The cells are fusiform or crescent-shaped, have no constriction at
180 BRITISH DESMIDIE^.
their centime, and are precisely like those of Closterium except in their aggregation, which is the only distinction between the two genera.
1. A. falcatus (Corda) j bundles of numerous crescent-shaped very slender cells.
Micrasterias falcata, Corda, Almanach de Carlsbad 1835, p. 121. t. 2. f. 29. Closterium gregarium, Meneghini, Cons]). Alg. Eugan.p. 17 (1837). Xanthidium? difforme, Ehr. Infus. p. 147. t. 10. f. 26 (1838)? Closterium falcatnm, Meneghini, Synop. Desmid. in LimicBa 1840, p. 233. Rhaphidium fasciculatum, Klitzing, Phycologia Germanica, p. 144 (1845). Ankistrodesmus gregarius, Brebisson, in lit. cum specimine (1846).
Dolgelley and Penzance, J. R. Sussex, Mr. Jenner. Ambleside, Mr. Sidebotham.
Italy, Meneghini. Germany, Ehrenberg, Kiitzing. Falaise, Brebisson.
Cells very minute and slender, crescent-shaped, fasciculated in irregular bundles composed of numerous individuals, which, as the convexity of each is turned inwards, diverge at each extremity of the bmidle.
This plant is not unlike an early state of a Closterium, and as such I formerly considered it ; but Corda, Kutziag and Brebisson have pronounced it to belong to a distinct genus.
The bvmdles vary greatly in their compactness, as well as in the number of their cells.
Not having seen Corda' s description and figure of Ankistrodesmus convo- lutus, I am unable to determine whether the present species differs from it.
Length of cell ^-i-g of an inch ; greatest breadth ytts'
Tab. XXXIV. fig. 3. a, b, c. aggregated cells ; d. a single cell.
**** Frond composed of few cells, definite in number, and not forming
a filament.
19. PEDIASTRUM, ilfe3/e«.
Frond plane, circular, composed of several cells, which form by their union a flattened star, and are generally arranged either in a single circle or in two or more concentric ones ; marginal cells bipartite.
Frond minute, composed of four or more cells united together in the figure of a flattened star ; when these are only four in number they are not arranged in a circle and the star is somewhat angular; in most species, however, they form either a single circle or two or more concentric ones, and one or two cells usually occupy the centre. The cells are combined into a frond by a mucous matrix, which is generally colourless and constitutes hyaline interstices. Occasionally some are ruptured, but in this case their endochrome alone escapes.
BRITISH DESMIDIE^. 181
and the others are not affected. In all the species the free margin of the outer cells is bipartite, a character which I consider important, and in fact a modification of the form observed in Cosmarium and other genera with constricted fronds. The cell in Pediastrum^ however, is different from theirs, since its division into two segments exists only on one side, and in regard to the inner cells is at most a slight con- cavity of the external margin.
The flat, star-like fronds of Pediastrum are so characteristic, that there is no risk of mistaking it for any other genus, Crucigenia per- haps excepted ; that however differs by having entire, quadrangular cells.
It is far more difficult to distinguish its species. Ehrenberg relies chiefly on the number of the circles, but this character, as Meneghini and Professor Bailey have observed, cannot always be depended on : the latter says, "^ There appears to me to be much confusion in the specific characters, arising from the circumstance that the number of corpuscles in the different rows has been made a character of spe- cific importance. From what I have seen of the species, I am satis- fied that the number of corpuscles in a star is liable to great variation in the same species."
I have myself noticed that, in one species at least, the number of circles varies from one to three ; and the same observation has been made by Mr. Jenner. He has also remarked that the number of cells in the inner circle, on which I was inclined to place greater reliance, is subject to variation. Some species have one cell in the centre and others two ; but the central cells are said to be sometimes deficient, a variation which I have not observed.
All the above characters, it must be allowed, are more or less un- certain ; still upon them we must for the most part depend in discri- minating between nearly allied species.
Meneghini adopts as a specific character the number and position of hyaline vesicles in each cell ; but I am afraid that both of these are also variable.
The synonyms in this genus are so confused that I quote them with much hesitation. Ehrenberg, having relied almost entirely on the number of the circles and the cells in each, has neglected the form of the cells, and consequently his species are intermixed, states of some being referred to others. Mr. Hassall indeed has constituted several new species ; but as he has attempted this from an examination merely
N 2
182 BRITISH DESMIDIE^.
of Ehrenberg's figures, and not of the plants themselves, his opinions are entitled to less weight than they would have been if founded on his own observation.
Professor Bailey has suggested, in his paper on the American Des- midieae, that the form of the cells might afford the most certain cha- racter. Kiitzing, who has described nine species in his * Phycologia Germanica,' seems to have arrived at the same conclusion. I have ventured in some instances to differ from Kiitzing's views ; yet I feel persuaded that his definitions of the species in Pediastrum are truer to nature than those of Ehrenberg.
I have not seen the cells during the process of division ; but I am informed by M. de Brebisson that it takes place at the notch, in the same manner as in other Desmidieae : hence the cells in each circle are connected at their ends, like those of the filamentous genera. I do not however understand in what manner the additional circles are formed, nor why the numbers in each circle are so constant.
The segments or lobes are in some species more or less emarginate, and in others entire ; as this character seems to be constant, I have taken advantage of it to divide the genus into two sections.
* Lobes of the outer cells emarginate, or truncate.
1. P. Tetras (Ehr.) ; cells four, separated by colourless interstices which form a cross ; lobes truncato-emarginate.
Micrasterias Tetras, Ehr. Infus. p. 155. t. 11. f. 1 (1838). Bailey, Amer.
Journ. of Science and Arts, v. 41. p. 293. t. 1. f. 19. Pediastrum Tetras, Ralfs, Annals of Nat. Hist. v. 14. p. 469. t. 12. f . 4
(1844) ; Trans, of Bat. Soc. of Edinburgh, v. 2. p. 157. t. 17. Hassall,
Brit. Freshwater Alg. p. 388.
Barmouth ; Dolgelley and Penzance, J. R. Beckley Furnace near Battle, Sussex, Mr. Jenner. Ambleside, Mr. Sideltotham. Near Aberdeen, Mr. P. Grant.
Germany, Ehrenberg. Maine to Virginia, Bailey.
Frond extremely minute, composed of four cells, which constitute a star-like figure ; the cells are somewhat triangular, and connected by a hyaline matrix, which forms colourless interstices in the figure of a cross ; the free margin is bilobed ; the lobes terminate in a broad shallow notch, which has acute corners. The colouring matter is pale green.
Menegbini makes Pediastrum Tetras a synonym of P. Heptactis ; but T have not seen any intermediate forms, and in fact the frond of this species is sometimes as large as that of P. Heptactis, although the latter contains twice as many cells.
BRITISH DESMIDIEiC. 183
Length of cell Yrrr of an inch ; breadth ^^Vr-
Tab. XXXI. fig. 1. a, b. fronds with endochrome ; e. distorted frond; d. empty frond.
2. P. Heptactis (Ehr.) ; frond constituted of seven cells disposed in a circle round another in its centre j cells bipartite with emarginate lobes.
Micmsterias heptactis, Ehr. Abh. d. Berl. Ak. (1833), p. 300 ; Infus. p. 156.
t. 11. f. 4. b, e, d. Euastrum hexagonum, Corda, Almanack de Carlsbad 1835, p. 122. f. 31. Pediastrum heptactis, Meneghiui, Synop. Desmid. in Linncea 1840, p. 211.
Ralfs, Annals of Nat. Hist. v. 14. p. 469. t. 12. f. 5 ; Trans, of Bat.
Soc. of Edinburgh, v. 2. p. 157. t. 17. Pediastrum simplex, HassaW, Brit. Freshwater Algce, p. 388 (1845) ; not of
other authors.
Barmouth and Penzance, /. R. Beckley Furnace, Sussex, and near South- ampton, Mr. Jenner. Rochdale, Mr. Coates. Near Aberdeen, Mr. P. Grant.
Germany, Ehrenberg and Corda. Mexico, Bailey.
Frond very minute, composed of eight cells, one in the centre and seven in a circle round it ; the cells connected by a gelatinous matrix, which forms colourless interstices. The seven external cells are bipartite, their lobes end- ing in a broad shallow notch with acute comers ; in other respects the cells are variable ; the figure of the central one especially differs in almost every specimen, being sometimes angular and entire, and sometimes deeply divided with rounded segments. The colouring matter is veiy pale.
Length of cell 2To^ ^i an inch ; breadth g-rVo •
Tab. XXXI. fig. 2. a, b. fronds with endochrome ; c. distorted frond ; d. empty frond.
3. P. biradiatum (Meyen) ; outer circle generally of eleven bipartite cells, with bifid or emarginate lobes.
/3. Lobes of outer cells truncato-emarginate.
Pediastrum. biradiatum, Meyen, Nov. Act. Acad. Nat. Cur. v. 14. f. 21, 22
(1828). Meueghini, Synop. Desmid. in LirmcBa 1840, p. 211. Micrasterias Rotida, Ehr. Infus. p. 158. t. 11. f. 7 (1838). Pediastrum Rotula, Kiitzmg, Phycologia Germanica, p. 143 (1845).
a. Penzance, J. R. Ambleside, Mr. Sidebotham. Rochdale, Mr. Coates. 13. Beckley Furnace, Sussex, and near Southampton, Mr. Jenner.
Germany, Meyen, Ehrenberg, Kutzing. New Jersey, Bailey.
Frond minute, generally composed of 1 6 or 17 cells arranged in two con- centric circles, with a solitary cell in the centre ; this central cell is said to be often wanting. I have never found it in British specimens, nor indeed even a vacancy in its place. The five angular cells forming the inner circle are often quadrilateral, and the exterior of each has a linear notch. The outer circle consists of eleven cells, which are either quadrilateral or somewhat cuneate ;
184 BRITISH DESMIDIE^.
the free margin is deeply bipartite, and the lobes are again divided or truncato- emarginate. The endochrome is bluish-green, with minute scattered granules. Interstices between the cells hyaline.
Kiitzing unites this and the two preceding species under Ehrenberg's name, Rotula ; Meneghini keeps it distinct. Typal specimens of this species differ from P. Tetras and P. Heptactis, not only in the number of the cells, but also in the deeply divided and tapermg lobes of the outer cells. Specimens how- ever of the variety /3, gathered in Sussex by Mr. Jenner, render it doubtful whether Kiitzing' s A-iew is not the correct one ; for whilst these specimens have the same number and disposition of cells as P. biradiatum, the lobes of their marginal cells are merely slightly emarginate like those of P. Heptactis.
Length of cell in the outer circle ^wos ^^ ^"^ '^^^^ 5 breadth ytTX'
Length of /3. -^^Vo 5 breadth ^^Vo-
Tab. XXXI. fig. 3. a. frond with endochrome ; b. empty frond : fig. 4. o, b. fronds of /3. with endochrome ; c. empty frond.
** Lobes of the segments entire.
t Connecting substance coloured.
4. P. Selencea (Kiitz.) ; cells crescent-shaped, arranged in one or more circles around one or two central ones ; connecting medium coloured.
Selencea orbicidar'is, Nitzsch, Kiitzing, Synopsis Diato7n. inLinnceal833,Tp. 604. Micrasterias Selencea, Kiitzing, Synop. Diatom, p. 604. f. 92 (1833). Micrasterias Boryana, Ehrenberg, Infusor. t. 11. f. 5. e (1838). Pediastrum Napoleonis, Ralfs, Annals of Nat. Hist. v. 14. p. 470. t. 12. f . 6
(1844) ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 158. t. 17 ; not of
Meneghini. Pediastrum Selencea, Kiitzing, Phycologia Germanica, p. 143? (1845). Pediastrum elegans, Hassall, British Freshtoater Algce, p. 389 (1845). Pediastrum lunare, Hassall, British Freshwater Algce, t. 92. f. 3 (1845).
Barmouth, North Wales, J. R.
Germany, Kiitzing, Ehrenberg.
Pediastrum Selencea, like the other species of this genus, varies in the number of cells. Kiitzing' s figures represent three states, ha-sang respectively one, two, and three circles, romid a central cell, all the cells being lunate ; the number of cells consisting of 5 in the first circle, 10 in the second, and 15 in the third.
The following description applies to British specimens only.
Frond minute, with two angular cells in the centre, and six crescent-shaped ones arranged in a circle round them. The cells are not approximate, or separated by hyaline interstices, as in other species ; but are connected by a coloured portion, which indeed may be said to constitute the frond, the cells being imbedded in it. It will be seen that the British specimens differ from those figured by Kiitzing by having two cells in the centre mstead of one, and six in the circle instead of five. I have never seen specimens with more than
RRITISH DESMIDIE^. 185
one circle. Notwitlistanding these differences, I believe that our plunt is cor- rectly referred to this species. It agrees both in the crescent-shaped cells and in the coloured connecting medium ; characters which distinguish it from all others.
Tab. XXXI. fig. 5. frond mth endochrome.
ft Interstices of the frond hyaline.
5. P. simplex (Meyen) ; frond composed of four cells with or without one or two central ones ; lobes of marginal cells ovate, tapering to a point.
a. Marginal cells truncate at the base and forming a circle, its centre vacant or occupied by one or two cells.
Pediastrum simplex, Meyen, Nov. Act. Acad. Nat. Cur. v. 14. t. 42. f. 1-3
(1828). Kiitzing, Phycolocjia Germanica, p. 142. Micrasterias simplex, Kiitzing, Synopsis Diatom. i?i Linncea 1833, p. 602. Micrasterias Coronula, Ehrenberg, Infusor. p. 156. t. 11. f. 2 (1838). Pediastrum. Napoleonis, Hassall, Brit. Freshwater Algce, t. 92. f. 10, 11
(1845).
/S. cruciatum ; cells angular at the base, connected in a cruciform manner without a central space.
Pediastrum cruciatum, Kiitzing, Phycoloyia Germanica, p. 142 (1845) ; in lit. cum icone.
Near Aberdeen, Mr. P. Grant. Germany, Kiitzing, Ehrenhery .
In all the specimens that I have seen of this species, the number of cells was invariably four ; but, according to Ehrenberg and other authors, it occasionally has one or two other cells in the centre. I have observed two forms : in one of them the cells were truncated at the base and the frond had a central square vacancy ; ui the other the bases of the cells extended into angles, and, as these exactly fitted each other, the interstices or joinings formed a cross. The latter state I believe to be the Pediastrum cruciatum of Kiitzing, although the figures which he sent me represent smaller fronds.
At the base of each cell in /3. there is generally a large vesicle, which how- ever is sometimes absent. At first sight this variety appears to be distinct, but I have seen interiuediate specimens, and, in all, the lobes of the cells are ovate at the base and taper into a cuspidate point.
Length of cell including lobes yoVo ^f an inch ; breadth ytsT '■> length of ^- tbVb- ; breadth from -^^ to -^^.
Tab. XXXIV. fig. 15. a. frond vdth endochrome ; b. empty frond ; e. frond of /3 ; d. P. cruciatum from a drawing by Kiitzing.
6. P. pertusum (Kiitz.) ; inner cells leaving hyaline intervals resem- bling foramina ; outer cells rectangular, notch triangular, as broad as the cell.
Micrasterias Boryana, Ehr. Infusor. t. II. f. 5. b, d, i (1838).
186 BRITISH DKSMIDIEiE.
Micrasterias tricyclia, Ehr. hifusor. t. 11. f. 8. a, 6 (1838). Pediastrum pertusum, Kiitzing, Phycologia Germanica, p. 143 (1845). Pediastrum triajclium, Hassall, Brit. Freshwater Algce, t. 92. f. 1 (1845).
Aberdeen, Mr. P. Grant. Storrington, Sussex, Mr. Jenner. Germany, Ehrenberg.
Frond consisting of from one to three circles of cells arranged round one or two central ones. The number of cells, as in Pediastrum Selencea and P. Boryanum, generally consists of 5 in the first circle, 1 0 in the second, and 1 5 in the third ; but I have seen fronds with four cells forming a circle about two central ones. Ehrenberg' s figures represent all the cells as alike in form, and this was the case in specimens sent me by Mr. P. Grant ; but Mr. Jenner finds the inner cells quadrate, and only the marginal ones notched. In all the varieties, however, the inner cells are so placed as to leave hyaline spaces which have the appearance of perforations. The marginal cells have, on their free side, a wide triangular notch, about equal to the fourth part of a square ; were this filled it would make the cell quadrate, consequently the sides and base of the cell form rectangular triangles, and the terminal lobes taper to an acute point.
Length of cell in outer circle ^ ^'gg of an inch ; breadth -g-^g-g-.
Tab. XXXI. fig. 6. a, b. fronds with endochrome.
7. P. granulatum (Kiitz.) ; cells granulated ; lobes of marginal cells tapering.
Pediastrum granulatum, Kiitzing, Phycologia Germanica, p. 143 (1845); in lit. cum icone.
"Weston Bogs near Southampton, Mr. Jenner.
Germany, Kiitzi^ig.
Frond composed of six cells circularly arranged around two subquadrate central ones ; the marginal cells have lobes gradually tapering into short points, and all are rough with minute granules.
I have seen no specimens of this species, but Mr. Jenner' s drawings exactly agree with one sent me by Professor Kiitzing.
Length of cell in outer circle -a-oVo ^^ ^^ ^^^^^ 5 breadth xiVr-
Tab. XXXI. fig. 8. a. frond with endochrome ; b. empty frond.
8. P. Najjoleonis (Turpin) ; six angular cells forming a circle round two central ones ; lobes of marginal cells cuspidate ; notch wide.
Helierella Napoleonis, Turpin, Bid. des Sc. Nat. par Levr. Atl. Veg. ves.
fig. 20 (1820) ; Mem. du Mus. v. 16. t. 13. f. 21. Micrasterias Napoleonis, Kiitzmg, Synop. Diatom, in Linncea 1833, p. 602.
Ehrenberg, Infus. p. 156. t. 11. f. 3. Pediastrum Napoleonis, Meneghini, Synop. Desmid. in Limicea 1840, p. 212. Pediastrimi hexactis, Hassall, Brit. Freshwater AlgcB, t. 92. f. 5 (1845). Pediastrum excavatum, Hassall, I. c. t. 92. f. 6 (1845).
Ashdown Forest, Sussex, Mr. Jenner. Swansea, J. R. Near Aberdeen, Mr. P. Grant.
Germany, Kiitzing, Ehrenberg.
BUITISH DESMIDIEJS. 187
I greatly doubt whether this species is distinct from Pediastrum Boryanum. Its claim to rank as a species depends on the number and arrangement of its cells. The cells themselves are variable in form. The notch of the marginal ones is rounded, and usually voider than in the allied species.
Length of cell in outer circle from y-jVg to Y4V3 of an mch ; breadth from _J to 1
1813" 1088'
Tab. XXXI. fig. 7. a, b, c. fronds with endochrome ; d, e. empty fronds.
9. P. angulosum (Ehr.) ; marginal cells with angular lobes which are not extended into rays ; interstices hyaline.
Micrasterias angulosa, Ehrenberg, Abh. der Berlin Ak. p. 301 (1833) ;
Infusor. p. 156. t. 11. f. 6. a. Pediastrum angulosum, Meneghini, Synopsis Desmid. inLinncea 1840, p. 211.
Hassall, Bi'itish Freshwater Algce, p. 391. Pediastrum Boryanum, Ralfs, Annals of Nat. Hist. v. 14. t, 12. f. 7 (upper
figure) (1844) ; Trans, of Bot. Soc. of Edinburgh, v. 2. t. 17.
Dolgelley, /. R. Ambleside, Mr. Sidebotham. Aberdeen, Mr. P. Grant. Beckley Furnace near Battle, Sussex, Mr. Jenner.
Germany, Ehrenberg.
Frond minute, consistmg of one or more circles of cells, with a single cell in the centre ; the number of cells are generally five in the inner circle, ten in the second, and fifteen in the third ; the inner cells are angular, and similar to those of Pediastrum Boryanum and P. vagutn. The marginal cells are less deeply notched than in those species, and the lobes are merely angular, not in the least extended into processes or rays. The angle is produced by the sloping of the outer margin, which frequently might be termed obliquely truncate, or almost emargmate.
Length of cell in outer circle -2^32" of an inch ; breadth -j-^j-a- Tab. XXXI. fig. 11. a. frond with endochrome; b, empty frond.
10. P. Boryanum (Turpin) ; cells arranged in one or more circles round one or two central ones ; marginal cells gradually tapering into two long subulate points ; notch narrow.
Helierella Boryana, Turpin, Diet, des Sc. Nat. par Levr. Atl. Veg. ves. f. 22
(1820) ; Mem. du Mus. v. 16. t. 13. f. 22. Micrasterias Boryi, Kiitzing, Synop. Diatom, in Linncea 1833, p. 603. Micrasterias Boi'yana, Ehrenberg, Abh. der Berlin Ak. p. 300 (1833) ;
Infus. p. 157. t. 11. f. 5. a, c, g, h. Pediastrum Boryanum, Meneghini, Synop. Desmid. in Linncea 1840, p. 210.
Ralfs, Annals of Nat. Hist. v. 14. p. 470. t. 12. f. 7 (lower figure) ;
Trans, of Bot. Soc. of Edinburgh, v. 2. p. 158. t. 17. Kiitzing, Phyc.
Germ. p. 143. Jeimer, Fl. of Tunbridge Wells, p. 198. Hassall, Brit.
Freshwater Algce, p. 389.
Dolgelley, Barmouth, and Penzance, J. R. Cheshunt, Mr. Hassall. Beckley Furnace near Battle, Storrington, Tunbridge Wells, &c., Sussex ; Dorking, Surrey ; and near Southampton, Mr. Jenner. Manchester, Mr. Gray and Mr. JVilliatnson.
188 BRITISH DESMID1E-(E.
Germany, KUtzing, Ehrenberg. Falaise, Brebisson. Maine to Mexico, Bailey.
Cells generally arranged in one to three circles round a central cell. The number of cells consists of five in the first circle, ten in the second, and fifteen in the third ; but these numbers are not invariable ; sometimes there are two central cells, and still more frequently the numbers in the circles differ from those just stated. The inner cells are five- or six-angled, broader than long, with a slight concavity on the outer margin ; the marginal cells are biradiate, the rays subulate, the notch narrow.
Pediastrum Boryanum differs from P. vagum in the gradually tapering acute lobes of the outer cells ; from P. angulosum it may be known by the lobes, which are elongated into rays, and not merely angular, as in that species.
Length of cell ia outer circle from -gVo" ^° rsVa ^^ ^"^ mch ; breadth from
I to 1
2 7 3 2 " 2 2 2 2*
Tab. XXXI. fig. 9. a. frond with endochrome ; b. empty frond.
1 1 . P. ellipticum (Ehr.) ; cells variable in number and arrangement ; lobes of marginal ones suddenly contracted into short, cylindrical, obtuse processes.
/3. processes of the lobes truncato-emarginate.
Micrasterias elliptica, Ehrenberg, Abh. der Berlin Ak. p. 302 (1833) ; Infiis.
p. 158. t. 11. f. 9. Micrasterias, No. 3, Bailey, American Journal of Science and Arts, v. 41.
p. 293. t. 1. f. 21 (1841). Pediastrum Boryanum, Ralfs, Annals of Nat. Hist. v. 14. t. 12. f. 8 (1844) ;
Trans, of Bat. Soc. of Edinburgh, v. 2. t. 17. Pediastrum vagum, Kiitzing, Phycologia Germanica, p. 143 (184.5) ; in lit.
cum icone. Pediastrum constrictum, Hassall, Brit. Freshwater Algce, p. 391 (1845). Pediastrum ellipticum, Hassall, Brit. Freshwater Algce, t. 92. f. 2 (1845).
Dolgelley, J. R. Aberdeenshire and Banffshire, Mr, P. Grant. Near Bristol, Mr. Thwaites. Beckley Furnace near Battle, Sussex ; Dorkmg, Surrey ; and near Southampton, Mr. Jenner.
Germany, Ehrenberg, Kutzing. Maine to Virgmia, Bailey.
Frond larger than that of any other species, often very irregular in form ; cells numerous, but varying much in number ; the arrangement of the inner ones, especially in the larger specimens, is more or less irregular, and not m distinct circles, like those in the preceding species. The notch of the mar- ginal cells is narrow, the lobes terminated by a cylindrical process, which appears to me rounded at its apex ; but Mr. Jenner usually finds two mmute teeth at the end.
Length of cell ui outer circle from yttj ^^ ¥W ^^ ^^^ ^i^*^^ ' breadth from _-J to —J
1515 ""^ 1020*
Tab. XXXI. fig. 10. a, b, c. fronds with endochrome ; d. empty frond.
BRITISH DESMIDIE^. 189
20. SCENEDESMUS, Meyen.
Frond composed of two to ten fusiform or oblong cells, arranged side by side in a single row, but after division in two alternating rows ; division oblique.
Cells always entire, and mostly fusiform or oblong, but in some species the outer ones are lunulate. There is no constriction nor su- ture at the middle, and the endochrome is not divided into two por- tions by a transverse band. The cells are few in number, varying from two to ten, and united into a frond by a hyaline matrix. Their division is oblique, and not transverse, as in most genera of the Desmidieaa. As all the cells divide simultaneously, the frond when dividing consists of two rows, which are retained in connection by the matrix for some time after the complete division of the cells. From the oblique manner of division, the cells of one row alternate with those of the other.
The dividing frond is so unlike one having only a single row of cells, that, in common with Meneghini and other naturalists, I formerly considered these states as different species ; and it was only on seeing a frond of Scenedesmus obtusus, in which the division of the cells was still incomplete, that I discovered my error. The fact however was previously known to Brebisson, and he has since sent me drawings illustrating the process.
The endochrome is in general very pale, and the starch granules are inconspicuous.
Scenedesmus differs from the preceding genera in the very different form of its cells, but Pediastrum supplies a connecting link between them. As in that genus, the frond in Scenedesmus is composed of several cells, but these are differently arranged ; and the division into two segments, which, although modified, is still met with in the outer cells of Pediastrum, is entirely absent in Scenedesmus. In the oblique manner in which its cells divide, it agrees with Spirotania, which however has a different arrangement of the endochrome, and a frond consisting merely of a single cell.
190 BRITISH DESMIDIEJE.
1. S. quadricauda (Turp.) ; cells generally four, oblong, rounded at their ends, disposed in a single row; each extremity of the two external ones usually terminated by a bristle.
Achnanthes quadricauda, Turpin, Diet, des Sc. Nat. par Levr. Atl. Veg. ves.
f. 8 (1820) ; Mem. du Mus. f. 6. Scenedesmiis magnus et S. longus,M.ejen, Nov. Act. Acad. Naf. Cur. v. 14. t.43.
f. 26-29 (1828). Kiitzing, St/uoj). Diatom, in Linncea 1833, p. 606. Scenedesmus quadricaudatus a. coriiutus, Ehr. Abh. d. Berl. Ak. 1833, p. 309.
Ralfs, Annals of Nat. Hist. v. 15. p. 402. t. 12. f. 4; Trans, of Bot.
Soc. of Edinburgh, v. 2. p. 159. t. 15. Hassall, Brit. Freshwater Algce,
p. 393. Scenedesmus quadricauda, Brebisson, Alg. Fal. p. 66 (1835). Menegh.
Synop. Desmid. in Linncea 1840, p. 206. Scenedesmus caudatus, Corda, Aim. de Cai'lsb. 1835, p. 123. t. 4. f. 50.
Kiitzing, Phy. Germ. p. 139. Arthrodesmus quadricaudattis, Ehr. Infus. p. 150. t. 10. f. 16 (1838). Bailey,
Amer. Journ. of Science and Arts, v. 41. p. 292. t. 1. f. 17.
/3. External cells with three bristles.
y. ecornis (Ehr.) ; all the cells similar, and without bristles.
Achnanthes quadrijuga, Turpin, Diet, des Sc. Nat. f. 5 (1820). Scenedesmus Leibleinii, Kutz. Leib. Bot. Zeit. 1830, f . 3 ; Synop. Diatom.
p. 607. Menegh. Synop. Desmid. p. 207. Scenedesmiis quadricaudatus (i. ecoimis, Ehr. Abh. d. Berl. Ak. 1833, p. 309.
Common. Wales and Cornwall, J. R. Sussex ; Kent ; and near South- ampton, Mr. Jenner. Bristol, Mr. Thwaites and Mr. Broome. Herts, Mr. Hassall. Ayrshire, Rev. D. Landsborough. Aberdeenshire and Banffshire, Mr. P. Grant. Northamptonshire, Rev. M. J. Berkeley. Kerry, Mr. An- drews. Manchester, Mr. Williamson. Ambleside, Mr. Sidebotham. Roch- dale, Mr. Coates.
Germany, Kiitzing, Ehrenberg, &c. Falaise, Brebisson. Maine to Vir- ginia, and in Mississippi River, Bailey.
Frond composed of from four to eight oblong cells, which are generally larger than those of any other species in the genus, about three times as long as broad, and rounded at their ends ; the external cells are usually the most turgid, and their bristles are directed outwards.
The colouring matter is pale, with minute scattered granules.
In /3. the cells are smaller, and the external ones, besides the usual terminal bristles, have another from the centre of the outer margin.
The variety y. is described by some authors as a distinct species ; but I agree with Ehrenberg in considering it a state of S. quadricauda, from which it differs only in having no bristles.
Length of cell y iVr ^^ ^^ ^"^^^ ' breadth -g-BVr-
Tab. XXXI. fig. \2.a,b,c, d. fronds with endochrome ; e,f. empty fronds ; g. variety /3 ; A. variety y; i. dividing frond of y.
BRITISH DESMIDIE^. 191
2. S. dimorphus (Turp.) ; cells acute, four to eight, placed evenly in a single row ; the inner cells fusiform, the outer externally lunate.
Achnanthes dimorpha, Turp. Diet, des Sc. Nat. par Lew. Atl. Veg. ves. f. 7 (1820).
Scenedesmus pectinatus, Meyen, Nov. Act. Acad. Nat. Cur. \. 14. p. 2. f. 34, 35 (1828). Kiitzing, Synop. Diatom, p. 608; Phij. Germ. p. 140. Brebisson i>i lit.
Scenedesmus dimorphus, Kiitzing, Synop. Diatotn. in Linncea 1833, p. 608. JMenegliini, Synop. Desmid. in Limicea 1840, p. 208. Ralfs, Annals of Nat. Hist. V. 15. p. 403. t. 12. f. 5 ; Trans, of Bot. Soc. of Edinburgh, V. 2. p. 160. t. 15. Hassall, Brit. Freshwater Algce, p. 393.
Arthrodesmus pectinatus, Ehr. Infus. p. 151. t. 10. f. 17 (1838).
Dolgelley and Penzance, J. R. Bristol, Mr. Thwaites. Manchester, Mr. Sidebotham and Mr. Williamson. Aberdeen, Mr. P. Grant. "Weston Bogs near Southampton, 3Ir. Jenner.
Germany, Kiitzing, Ehrenberg, Cor da, &c. Falaise, Brebisson.
Frond very minute, consisting of four to eight cells placed evenly side by side in a single row ; the inner cells straight, fusiform, attenuated, and acute at each end ; the outer ones externally lunate. The endochrome is pale bluish- green.
Length of cell from yoVo ^'^ '^h^ ^^ ^^ '\nc}i ; breadth ^^Vo • Tab. XXXI. fig. 13. a. frond with endochrome ; b. empty frond.
3. S. acutus (Meyen) ; cells two to eight, fusiform, acuminate, arranged in a single, irregularly alternating series.
Scenedesmus acutus, Meyen, Nov. Act. Acad. Nat. Cur. v. 14. t. 43. f. 32 (1828). Kiitzing, Synop. Diatom, in Linncea 1833, p. 609. f. 96 ; Phycologia Germanica, p. 139. Meneghini, Sytiop. Desmid. in Linncea 1840, p. 207. Ralfs, Annals of Nat. Hist. v. 15. p. 403. t. 12. f. 6 ; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 160. t. 15. Hassall, Brit. Freshwater Algae, p. 393.
Scenedesmus fusif or mis, Meneghini, Consp. Alg. Eugan. p. 18 (1837) ; Synop. Desmid. in Linncea 1840, p. 208.
Arthrodesmus acutus, Ehrenberg, Infusor. p. 150. t. 10. f. 19 (1838).
King's Cliffe, Northamptonshire, Rev. M. J. Berkeley. Bristol, Mr. Thwaites. Dolgelley, /. R. Weston Bogs near Southampton, Mr. Jenner.
Germany, Ehrenberg, Kiitzing. Falaise, Brebisson.
Cells fusiform, acute at each end, frequently more or less ventricose ; after di\'ision forming a single series, but projecting alternately more or less on each margin. The two outer cells are frequently crescent-shaped.
When the cells are nearly uniform this species has some resemblance to Scenedesmus dimorphus ; but in the latter the cells are more slender, never ventricose, and are arranged quite evenly side by side. It is more difficult to distinguish S. acutus from S. obliqiius, and I am far from certain that Ehren- berg erred in uniting them. The principal distinction is that in S. acutus
192 BRITISH DESMIDIE^.
the cells form only a single series, which is nevertheless irregular on account of the alternate projection of the cells in opposite directions. In ^S". obliquus, on the other hand, the cells by division form two distinct rows, which, after separation, become two fronds.
Length of cell from xoVs ^^ 10^20 ^^ ^^ ^^'^^^ '■> breadth from ^-jVt ^^ Tstt' Tab. XXXI. fig. 14. perfect frond. Tab. XXXIV. fig. 16. distorted variety.
4. S. obliquus (Turpin) ; cells elliptico-fusiform, after division arranged in two distinct, generally oblique series, the outermost cell of each not in contact with any of those in the other series.
Achnanthes ohliqua, Turpin, Diet, des Sc. Nat. par Lew. Atl. Veg. ves. f. 9
(1820) ; Mem. du Mus. v. 16. t. 13. f. 9. Scenedesmus obliquus, Kiitzing, Synop. Diatom, in Linncea 1833, p. 609.
Meneghini, Synop. Destnid. in Linncea 1840, p. 208. Berkeley, English
Botany, t. 2933. Scenedesmus triseriatus, Meneghini, Conspect. Alg. Eugan. p. 18 (1837) ;
Synop. Desmid. in Linncea 1840, p. 208. Ralfs, Annals of Nat. Hist.
V. 1.5. p. 403. t. 12. f. 7; Trans, of Bot. Soc. of Edinburgh, v. 2. p. 161.
t. 15. Arthrodesmus acutus, Ehrenberg, Infusor. t. 10. f. 19. b (1838).
King's Cliflfe, Rev. M, J. Berkeley. Near Bristol, Mr. Thwaites. Ayrshire, Rev. D. Landsborough. Near Manchester, Mr. Sidebotham. Dolgelley and Penzance, J. R. Near Aberdeen, Mr. P. Grant and Br. Bickie. Storrington, Sussex ; and Weston Bogs near Southampton, Mr. Jenner.
Germany, Kiitzing, Ehrenberg. Italy, Meneghini. Falaise, Br^bisson.
Scenedesmus obliquus approaches very closely to Scenedesmus acutus, and the principal distiuction depends on the different appearances presented by the dividing frond ; and as this plant is most commonly seen in that state, I shall so describe it, merely premising that when separated, the frond consists of only one row. Mr. Berkeley has united S. triseriatus to S. obliquus, and I readily follow his example.
The cells are eight in number, arranged obliquely in two distinct series. Each series has three cells, which are fusiform, equal, somewhat ventricose in the middle, acute at the free extremity, and subacute or romided at the inner one. As the cells are not placed evenly, but each projects beyond its neigh- bour, the rows are oblique ; their position with respect to each other is such that the inner ends of two cells of the lower lie between those of the upper row, whilst that of the third is outside the end of the highest in the upper. Of the two remaining cells, which are lunate, one is placed beyond the outer cell in each series, and is therefore not in contact with any cell in the other. They however take the same direction as the other cells in the series to which they respectively belong.
The different species of Scenedesmus frequently make their appearance in clear water that is kept in glasses or bottles and exposed to the light. I have received specimens of this species collected in this manner from Mr. Lands- borough and Mr. Berkeley, and have myself repeatedly noticed its appearance in bottles containing other Desmidiese, and sometimes its rapid increase so as
BRITISH DRSMIDIEilS. 193
to outnumber its companions. I must however observe, that specimens thus obt.iined are more variable in their characters than su.ch as are gathered ui their native abodes, and that their cells are frequently more or less distorted.
Length of cell ^-gVir of ^^^ i"^^ '■> breadth ^^Vo •
Tab. XXXI. fig. 15. a, b, c. different states of frond.
5. S. obtums (Meyen); cells three to eight, ovate or oblong, and arranged in one row, or, after division, alternately in two rows.
Achnanthes quadralterna et octalterna, Turp. Diet, des Sc. Nat. par Levr. Atl. Veg. res. f. 7, 8 (1820).
Scenedesnms obtusus, Meyen, Nov. Act. Acad. Nat. Cur. v. 14.f. 31 (1828). Meneghini, St/iwj}. Desmid. in Linncea 1840, p. 208. Ralfs, Annals of Nat. Hist. V. 15. p. 404. t. 12. f. 8 ; Trans, of Bot. Sac. of Edinburgh, V. 2. p. 162. t. 15. KUtziug, Phij. Germ. p. 139. Hassall, i?/7Y. Fresh- water Algce, p. 394.
Scenedesmus qiiadr alt emus, KUtz. Synop. Diatom, in Linncea 1833, p. 608. f. 94.
Scenedesmus octoalternus, Kiitzing, /. c. p. 609. f. 95.
Arthrodesmus acutusi, Bailey, Amer. Journ. of Science and Arts, v. 41. p. 292. t. 1. f. 18 (1841).
Common. Dolgelley and Penzance, J. R. Storrington and Beckley Fur- nace near Battle, Sussex ; Reigate, Surrey ; and near Southampton, Mr. Jenner. Bristol, Mr. Thwaites. Manchester, Mr. Williamson. Ambleside, Mr. Side- botham. Aberdeenshire, Mr. P. Grant.
Germany, Kiitzing. Falaise, Brebisson. Maine to Virginia, and in the Mississippi River, Bailey.
Frond minute, composed of from three to eight ovate or ovato-oblong cells vnth rounded ends. The endochrome is very pale green.
This species is rarely met with in a simple state, but as the cells after AvA- sion are still retained in connection by the mucous matrix, two rows are usually present, the broader ends of one row lying between the cells of the other. The hyaline matrix is frequently theu' only bond of union, and in this state they seem to connect the Desmidieae with the Ulvaceee through Merismo- pedia.
Length of cell from ^3^3^ to yg^r of ^"^ "i^h ; greatest breadth from xoW
to
362 3*
Tab, XXXI. fig. 16. a, b. ordinary state of frond; c. frond just divided.
6. S. duplex (Kiitz.) ; cells slender, fusiform, sigmoid, tapering at each end into a fine point ; after division closely connected for about half their length.
Rhaphidium duplex, Kiitzing, Phycologia Germanica, p. 144 (1845). Penzance, J. R. Germany, Kiitzing.
Cells linear-lanceolate ; extremities tapering to a fine point and curved in opposite directions. The cells after division remain closely united ; frequently
194 BRITISH DESMIDIE^.
the frond consists of only a single pair of cells so connected, but sometimes of two or even three of these pairs, which however are remote from each other : in this case, as the connecting mucus is colourless, they look hke distinct plants, and their relation can be detected only by moving the frond. If kept in water for a few days, the cells separate from each other.
Professor Kiitzing formed his genus Rhaphidium for the reception of the plant above described and a species of Ankistrodesmua ; but I beheve the proper position of the former is in this genus.
Tab. XXXIV. fig. 17. a. frond with dividing cells ; b. cell with the division more advanced.
195
ANALYSIS OF THE GENERA.
1 . Frond a single cell (its division being followed by separation),
or cells fasciculated 2
Frond composed of several cells 13
2. Segments, in the front view of the frond, lobed, incised, si-
nuated, or notched 3
Segments, in the front view, undivided 4
3. Frond fusiform ; segments notched at the end, otherwise
entire Tetmemorus.
Frond oblong, compressed ; segments sinuated Euastrum.
Frond lenticular ; lobes of segments incised or bidentate
at the apex Micrasterias.
4. End view of frond angular or radiate 5
End view of frond neither angular nor radiate 6
5. Processes geminate from each angle, one external to the
other Didymocladon.
Processes, if present, with their di\'isions on the same
plane Staurastruni.
6. Cells short, rarely more than twice as long as broad 7
Cells elongated (cylindrical, fusiform or Innately curved) 9
7. Frond with elongated, simple or branched spines 8
Frond not spinous Cosmarium.
8. Segments with two spines Arthrodesmus.
Segments with four or more spines Xanthidium.
9. Cells straight 10
Cells curved 12
10. Endochrome spiral Spirotcenia.
Endochrome not spiral II
1 1 . Frond moderately elongated, if linear not constricted at the
middle, and its segments not inflated at the base Peniiim.
Frond much elongated, linear, generally much constricted at
the middle, and its segments inflated at the base Docidium.
o
196 BRITISH DESMIDIE^.
12. Cells not fasciculated Closterium.
Cells fasciculated Ankistrodesmus.
13. Frond an elongated jointed filament 14
Frond of few cells not forming a filament 18
14. Filament plane or triangular, with junction-glands or fora-
mina between the joints 15
Filament never plane ; neither glands nor foramina between
the joints 16
15. Joints with junction-glands; their margins incised or si-
nuated Sphcerozosma.
Joints with foramina between them; their margins bicre-
nate or entire Aptogonum.
16. Filament triangular or quadrangular Desmidium.
Filament cylindrical or subcylindrical 17
1 7. Joints surrounded by a groove Hyalotheca.
Joints with two opposite bicrenate projections Bidymoprium.
18. Cells arranged in the form of a flattened star Pediastrum.
Cells placed side by side in one or two rows Scenedesmus.
ANALYSIS OF THE SPECIES.
1. Hyalotheca.
Fragile ; joints bicrenate dissiliens.
Scarcely fragile ; joints with a minute bifid projection mucosa.
2. DiDYMOPRIVM.
Joints broader than long ; with angular teeth Grevillii.
Joints longer than broad ; with rounded crenatures Borreri.
3. Desmidium.
Filament triangular Swai'tzii.
Filament quadrangular quadrangulatum.
4. Aptogonum.
Desmidium.
5. Sph^rozosma.
Constriction of joints a linear notch on each margin .... vertehratum. Constriction a broad sinus on each margin excavatum.
BRITISH DESMIDIEyE. 19/
6. MiCRASTERIAS.
1 . Lobes of segments radiate, incised and cuneate 2
Lobes horizontal, tapering and bidentate 12
2. Frond orbiciUar or oblong ; lobes and subdivisions approximate .... 3 Frond subelliptic ; end lobe exserted 10
3. Frond oblong Jenneri.
Frond orbicular 4
4. End lobes broadest 5
End lobes narrow 6
5. End margin convex crenata.
End margin truncate or concave truncata.
6. Principal divisions of the frond bordered with puncta-like
granules papillifera.
Surface of frond smooth , 7
7. Ultimate subdivision of lateral lobes inflated and tapering .... radiosa. Ultimate subdivisions tnmcate 8
8. Extremities of subdivisions neither spinous nor mucronate. . denticulata. Extremities of subdivisions either spinous or mucronate 9
9. Extremities of subdivisions abrupt with acute or spinous angles. . rotata. Extremities of subdivisions rounded and furnished with two
mucros Jimbriata.
10. Angles of end lobe bipartite ; lateral lobes toothed americana.
Angles of end lobe bidentate ; lateral lobes deeply divided 11
1 1 . Subdivisions of lobes long, narrow-linear furcata.
Subdivisions of lobes short, scarcely linear Crux-Melitensis.
1 2. End margin convex ; lobes conical oscitans.
End margin straight ; lobes triangular pinnatifida.
7. EUASTRUM.
1 . Terminal lobe distinct, cuneate, included in a notch formed
by the lateral lobes 2
Terminal lobe exserted or indistinct 4
2. Frond rough ; end margin sinuated verrucosum.
Frond smooth ; terminal notch linear 3
3. Segments 5-lobed oblongum.
Segments 3-lobed crassum.
4. Segments vdth a distinct, narrow, terminal notch 5
Segments with the end margin straight or slightly concave 15
o 2
198 BRITISH DESMIDIE^.
5. Ends protuberant or pouting ; angles usually terminated by
a spine 6
End straight or convex 7
6. End projections angular and tootb-like rostratum.
End projections pouting and rounded elegans.
7. End lobe distinct, dilated, and connected to the basal por-
tion by a distinct neck 8
End lobe obscure, not dilated 12
8. Transverse view with straight or concave sides ; neck very
long insigne.
Transverse view with inflated or lobed middle 9
9. Segments distinctly 5-lobed pinnatum.
Segments not 5-lobed 10
10. Neck of segments included between the process-like elon-
gations of middle lobes , humerosum.
Neck exserted 11
1 1 . Segments inflated at the base ampullaceum.
Segments pyramidal, not inflated affine.
1 2. End margin truncate, with acute angles binale.
Ends rounded 13
13. Segments cuneiform, not lobed cuneatum.
Segments either lobed or contracted upwards into a neck
(not cuneiform) 14
14. Transverse view with one protuberance on each side ansatum.
Transverse view with three protuberances on each side circulare.
Transverse view with four protuberances on each side Didelta.
15. End lobe distinct, dilated and joined to the basal portion by a neck. 16 Margins sinuated but not lobed sublobatum.
16. Protuberances smooth ; end margin straight pectinatum.
Protuberances granulated ; end margin concave gemmatum.
8. COSMARIUM.
1 . Constriction forming a linear notch on each side ; end view
not circular 2
Constriction not forming notches at the sides ; end view circular. . 24
2. Segments smooth, entire 3
Segments crenate or margined by pearly granules 9
3. Frond lenticular JRalfsii.
Frond not lenticular 4
BRITISH DESMIDIE.E. 199
4 . Frond as broad as or broader than long 6
Frond longer than broad 7
5. Segments reniform ; end view with a slight lobe on each side
at the middle Phaseolus.
Segments elliptic in both front and end views 6
6. Empty frond reddish ; notches closed tinctum.
Empty frond hyaline ; notches gaping bioculatum.
7. Ends romided Cucumis.
Ends tnmcate *^
8. Segments quadrate quadratum.
Segments oval with flattened ends pyramidatum.
Segments truncato-triangular granatum.
9. End view elliptic 10
End view with a lobe at the middle of each side 19
10. Frond smooth, crenate 11
Frond rough with pearly granules which give a denticulate
appearance to the margin 13
1 1 . Sides and end of segments bicrenate Meneghinii.
Segments with many crenatures 12
12. Segments with flattened, minutely crenate ends; spines of
sporangium very short crenatum.
Segments with rounded, strongly crenate ends ; spines of spo- rangium elongated undulatum.
13. Segments truncato-triangular Botrytis.
Segments not in the least triangular 14
14. Frond elliptic ; granules large and confined to the margin ovale.
Frond not elliptic ; granules not confined to the margin 15
15. Frond twice as long as broad, with parallel sides amoenum.
Frond not twice as long as broad ; sides not parallel 16
16. Segments quadrangular ' conspersum.
Segments rounded 17
1 7. Pearly granules longer than broad Brebissonii.
Pearly granides broader than long 18
18. Granules giving a crenate appearance to the margin . . tetraophthabnum . Granules giving a denticulate appearance to the margin, margaritiferum.
19. Segments bordered by papillae-like granules ; end view with
truncate ends cristatiim.
Pearly granules neither papillse-like nor confined to the mar- gin ; end view with rounded ends 20
20. Segments bordered with denticulated crenatiues ccBlatum.
Segments not crenate 21
200 BRITISH DESMIDIEiE.
2 1 . Segments reniform, three times broader than long .... commissurale. Segments not reniform, about twice as broad as long 22
22. End margin straight Broomeii.
End margin not straight 23
23. Inflation reaching to or beyond the end margin ornatum.
Inflation confined to the centre of the segment . . biretum.
24. Frond rough with pearly granules which give a denticulate
appearance to the margin 25
Frond smooth ; margin entire 26
25. Segments spherical orbiculatum.
Segments subquadrate cylindricum.
26. Segments spherical , moniliforme.
Segments not spherical 27
27. Segments broader than long (hemispherical or semi-oval) . . connatum. Segments as long as or longer than broad 28
28. Frond (oval) large, distinctly visible to the naked eye turgidum.
Frond minute, scarcely visible to the naked eye 29
29. Frond fusiform or oblong 30
Frond not tapering ; ends broadly rounded 31
30. Puncta distinct Cucurbita.
Puncta wanting, or very indistinct Thwaitesii.
31 . Endochrome in longitudinal fillets curtum,
Endochrome not in fillets attenuatum.
9. Xanthidium.
1 . Spines divided at the apex armatum.
Spines subulate 2
2. Segment without central projections, its spines usually four . ? octocorne. Segment with central projections ; spines eight or more 3
3. Spines scattered aculeatum.
Spines marginal, in pairs 4
4. Segments with a solitary basal spine on each side, the rest
in pairs cristatum.
Segments with basal spines in pairs 5
5. Central projections minute and smooth in end view .... fascieulatum. Central projections prominent and denticulate in end view . . JBrebissonii.
10. Arthrodesmus.
Segments elliptic coiivergens.
Segments with truncate ends Incus.
BRITISH DESMIDIEiC. 201
11. Staurastrum.
1 . Frond neither rough nor spmous ; angles in end view broadly rounded. 2 Frond either rough, spinous, or with elongated angles 5
2. Angles with a minute nipple-like projection 3
Angles rounded, without a projection 4
3. Sides convex tumidum.
Sides concave hrevispina (3.
4. Segments elliptic in the front view niuticum.
Segments semiorbicular in the front view orbiculare.
5. Frond with awned inflated angles, but without other spines 6
Frond either awnless or ha\ang other spines besides the awns .... 11
6. Frond rough with minute granules lunatum.
Frond smooth 7
7. Segments connected by a ribbon-like band cuspidatum.
Segments connected vdthout a band 8
8. Awns, in front view, terminating conical lobes aristiferum.
Awns, in front view, not terminating lobes 9
9. Awns straight, rarely converging ; segments, if elliptic, not
turgid dejectum.
Awns curved and converging ; segments turgid-elliptic 10
10. Segments inflated ; awns inconspicuous brevispina.
Segments turgid ; awns distinct Bickiei.
1 1 . Frond smooth, glabrous ; angles prolonged into processes
divided at the apex 12
Frond either rough, spinous or dentate ; divided processes,
if any, rough 13
12. End view with an elongated process from each angle .... brachiatum. End view with short geminate processes from each lobe Iceve.
13. Frond with simple, acute, uniform spines; angles in end
view broadly rounded and entire 14
Frond, if spinous, either with some or all of its spines not
subulate, or with angles not rounded in the end view 16
14. Segments quadrangular in the front view Hystrix.
Segments semi-orbicular or reniform in the front view 15
15. Spines conico-triangiUar ; end view of frond with convex sides, murieatum. Spines hair-like ; end view of frond with convex or slightly
concave sides hirsutum.
Spines thom-hke ; end view of frond with very concave sides, teliferum.
16. Segments quadrangular in the front view quad r angular e.
Segments not quadrangular in the front view 17
202 BRITISH DESMIDIE^.
17. Segments in front view with a forked spine on each side,
otherwise smooth , Avicula.
Segments in front view having many spines or none 18
18. Frond smooth ; end view acutely triangular, with two acute
accessory spines to each angle 19
Frond rough or spinous ; angles in the end view not acute 20
1 9. Segments in the front view with a forked spine on each side, monticulosum. Segments in the front view with all their spines slender,
simple, and directed outwards pungens.
20. Frond rough with large granules ; end view with five or six
rounded and toothed lohes sexcostatum.
Frond either minutely granulate or spinous ; angles in end
view either entire or elongated into rays 21
2 1 . Frond rough with puncta-like granules ; angles or rays in
end view entire 22
Frond either spinous or having the angles or rays tipped with spines 28
22. End view with rounded or truncate short rays or angles 23
End view with elongated slender rays or processes 27
23. End view with slightly concave sides and hroadly rounded
angles punctulatum.
End view either with very concave sides or with angles
elongated into short rays 24
24. End view triangular 25
End view with four or more angles or rays 26
25. Segments rounded on each side alternans.
Segments tapering on each side into a short process tricorne,
26. Segments twice as broad as long ; end view 4-rayed dilatatum.
Segments as long as broad ; end view 5- to 7-rayed . . margaritaceum,
27. Segments with converging processes Arachne.
Segments with diverging processes tetracerum.
28. Frond rough with minute granules ; spines, besides those
that tip the rays, few and inconspicuous, or none 29
Frond with evident, more or less forked or emarguiate spines .... 33
29. Processes much elongated 30
Processes short 31
30. Processes divergent in the front view paradoxum.
Processes parallel in the front view gracile.
31. Processes convergent in the front view cyrtocerum.
Processes nearly straight in the front view 32
32. Segments fusiform tricorne ft.
Segments ventricose, not fusiform polymorphum.
BRITISH DESMIDIEiE. 203
33. End view with broad, emarginate or bifid lobes enonne.
End view with the angles either rounded or tapering into lobes . . 34
34. Spines scarcely distinguishable from the associated granules . . asjoerum. Sphies distinct 35
35. End A'iew with convex sides and rounded angles, and fringed
with stout forked spines spongiosum.
End \-iew with concave sides ; angles not rounded 36
36. Each angle in end view terminated by a spine with two
accessory spines spinosum.
Each angle in end view tapering into a process tipped by
three or four acute pomts or spines 37
37. Each side in end view with two slender forked spines, with
or without other spines ; rays slender vestitum.
End view without slender forked spines at the sides ; rays short, stout. 38
38. Rays curved in end view controversum.
Rays straight in end view aculeatum.
12. DiDYMOCLADON.
furcigerus.
13. Tetmemorus.
1 . Frond fusiform in the front view ; puncta distinct, scattered, granulatus. Frond not fusiform in the front view ; puncta either very in- distinct or in longitudinal rows 2
2. Pmicta distinct, in longitudinal rows Brebissonii.
Puncta either wanting or indistinct and scattered l<svis.
14. Penium.
1 . Frond granulate or striate 2
Frond smooth 3
2. Granules arranged in longitudinal rows margaritaceum.
Granules scattered Cylindrus.
3. Endochrome transversely divided into four portions .... interruptum. Endochrome not divided into more than two portions 4
4. Frond lanceolate, fusiform or elliptic 5
Frond cylindrical 6
5. Frond elliptic ; fillets undulating Big it us.
Frond lanceolate or fusiform ; fillets straight dosterioides.
6. Ends truncate tmncatum.
Ends rounded 7
204 BRITISH DESMIDIE^.
7. Sporangium orbicular ; conjugated fronds deciduous Jenneri.
Sporangium at first quadrate ; conjugated fronds persistent. Brebissonii.
15. DOCIDIUM.
1 . Frond neither constricted nor inflated 1 asperum.
Frond constricted ; segments mostly inflated at the base 2
2. Suture inconspicuous ; segments not inflated minutum.
Suture distinct ; segments mflated at their base 3
3. Frond stout ; suture projecting at the sides .... 4
Frond slender ; suture not projecting 5
4. Segments with one inflation ; extremities attenuated truncatum.
Segments with several inflations ; extremities not attenuated, nodulosum.
5. Extremities clavate clavatum.
Extremities not clavate 6
6. Ends bordered with tubercles Ehrenbergii.
Ends destitute of tubercles Baculum.
16. Closterium.
1. Frond suddenly constricted at each end into a conical point, attenuatum. Frond not constricted at the ends 2
2. Frond striated, tapering into a beak at each end, lower
margin prominent at the middle 3
Frond not rostrate ; if striated, its lower margin not pro- minent at the middle 6
3. Beaks setaceous, as long as or longer than the body 4
Beaks linear, much shorter than the body 5
4. Beaks much longer than the body setaceum.
Beaks about as long as the body rostratum.
5. Frond much inflated at the middle, rapidly tapering at each end. Ralfsii. Frond slightly inflated at the middle, gradually tapering at
each end lineatum.
6. Frond minute, acicular ; sporangium cruciform 7
Frond not acicular ; sporangium orbicular 8
7. Ends obtuse Coimu.
Ends acute acutum.
8. Frond semilunate or semilanceolate, the lower margin in-
clined upwards at the ends 9
Frond having either truncate ends or its lower margin
inclined downwards at the ends _ 12
I). Vesicles numerous, scattered Lunula.
Vesicles in a longitudinal row 10
BRITISH DESMIDIE^. 205
10. Ends of frond slightly curved upwards ; striae distinct .... turyidum. Ends of frond straight ; striae none or indistinct 11
1 1 . Frond linear-lanceolate ; ends conical, obtuse acerosum.
Frond semilanceolate ; ends subacute lanceolatum.
1 2. Frond smooth, crescent-shaped 13
Frond either not crescent-shaped or else distinctly striated 17
13. Vesicles numerous, scattered Ehrenbergii.
Vesicles in a longitudinal row 14
14. Empty frond colourless ; ends romided 15
Empty frond usually reddish ; ends subacute 16
15. Lower margin of frond inflated at the middle moniliferum.
Frond not inflated at the middle Jenneri.
16. Frond inflated at the middle Leibleinii.
Frond slender, not inflated at the middle Dianee.
1 7. Lower margin of frond inclined upwards at the trimcate
ends ; striae none or indistinct didymotocum.
Ends of frond inchned downwards ; striae distinct 18
18. Striae three to seven, prominent 19
Striae numerous, fine 20
19. Frond semilunate or crescent-shaped costatum.
Frond huear angustatum.
20. Frond narrow-linear, nearly straight juncidum.
Frond tapering, curved 21
21. Striae crowded ; sutures one to three striolatum.
Striae not crowded ; sutures usually more than three .... intermedium.
17. Spirot^nia.
Spire solitary, broad, conspicuous condensata.
Spires several, narrow, obscure , . . . obscura.
18. Ankistrodesmus. falcatus.
19. Pediastrum.
1 . Lobes of marginal cells bifid or truncato-emarginate 2
Lobes of marginal cells entire 3
2. Cells four Tetras.
Cells seven, circularly disposed round a central one Heptactis.
Cells eleven, circularly disposed round five or six central ones, biradiatum.
3. Marginal cells crescent-shaped ; connecting substance coloured. Selenoea. Cells not crescent-shaped ; connecting substance hyaUne 4
206 BRITISH DESMIDIEJE.
4. Cells granulate granulatum.
Cells smooth 5
5. Lobes of marginal cells terminated by obtuse processes .... ellipticum. Lobes of marginal cells acute 6
6. Marginal cells with notches as wide as the cells pertusum.
Notches much narrower than the cells 7
7. Marginal cells four simplex.
Marginal cells more than four 8
8. Six cells circularly disposed romid two central ones Napoleonis.
Cells arranged in two or more circles 9
9. Lobes of marginal cells angular, not tapering , angulosum.
Lobes of marginal cells tapering Boryanum.
20. SCENEDESMUS.
1 . Cells obtuse 2
Cells acute or acuminate 3
2. Cells cylindrical or oblong quadricauda.
Cells ovate obtusus.
3. Cells ventricose at the middle 4
Cells slender, not at all ventricose 5
4. Cells in a single zigzag row acutus.
Cells either in two rows or not zigzag obliquus.
5. Outer cells crescent-shaped, inner straight, all approximate, dimorphus. Cells curved, distant duplex.
APPENDIX.
LIST OF SPECIES NOT HITHERTO DETECTED IN BRITAIN.
HYALOTHECA, Ehr.
3. H. ? duhia (Kiitz.) ; filament without a mucous tube ; joints rather broader than long, with two puncta near each margin.
Hyalothecal duhia, Kutzing, Phycologia Germanica, p. 140 (1845) ; in lit. cum icone.
Nordhausen, Prussia, Kutzing.
Tab. XXXV. fig. 16. portion of a filament from a drawing by Professor Kutzing.
DESMIDIUM, Ag.
3. D. undulatmn (Corda) ; joints with four crenatures at each margin.
Besmidium undulatum, Corda, Observations Microscopiques sur les Ani- malcules des eaux et des thermes de Carlsbad, p. 19. t. 4. f. 27 (1840).
Carlsbad ; Prague ; and Reichenberg, Corda.
The constriction of the joints is marked by slight marginal notches, on each side of which are two broad crenatures.
Desmidium undulatum appears to be a distinct species, differing from D. Swartzii by having bicrenate segments.
4. D. didymum (Corda).
Desmidium didymum, Corda, Aim. de Carlsbad 1835, p. 123. t. 4. f. 43. Kiitzing, Phyc. Germ. p. 141.
Carlsbad, Corda.
Ehrenberg and Meueghini unite J)esinidium didymum (Corda) to D. bijidum (Ehr.), which the latter describes as a filamentous plant. Kutzing removes Z>. bijidum to Staurastrum, but retains the present plant in Desmidium, of
208 BRITISH DESMIDIE^.
which Corda considers that both are true species. I have not seen Corda's descriptions or figures, but in a subsequent work he gives the following reasons under D. hifidum for beheving them distinct : —
"M. Ehrenberg lui adjoint I'espece suivante, trouvee a Carlsbad. EUe en differe totalement, du moins de celle que je considere comme la forme normale du Desmidium hifidum, qui, relativement a sa structure, principalement a la decoupure de ses pointes, correspond beaucoup avec le dessin incomplet d'un membre separe, qu'on trouve dans I'ouvrage de M. Ehrenberg, I. c. D. hifidum {hidens dans le dessin), vu lateralement, ne presente que deux pointes prin- cipales sur chaque aile, lesquelles sont simples. Quant a I'espece suivante, nous avons depeint deux pointes principales, tres-visibles, et chacune d'elles egalement pourvue de deux pointes." — Ohserv. Microscop. sur les Animalcules de Carlshad, p. 18.
5. D. hifidum (Ehr.). See Staurastrum hifidum.
APTOGONUM.
2. A. Baileyi ; filament not crenated ; joints about equal in
length and breadth.
Odontellal tridentata, Bailey, in lit. cum icone (1846).
Worden's Pond, Rhode Island ; near Princeton, New Jersey, with spo- rangia, Bailey.
Filament triangular ; joints excavated at their junction like those of Apto- gonum Desmidium. The joints are not bicrenate, hence the margins of the filament are entire, a character which distinguishes it from that species. The end view is triangular, with rounded angles.
Professor Bailey has sent me a drawing of the conjugated state, very in- teresting from its resemblance to a condition oi Desmidium Swartzii, ^Nhic\\ I had doubtfully regarded as the sporangia of that species. In both plants it is difficult to understand the process or to distinguish the coupled filaments, since the appearance is merely that of a much-enlarged and torn filament.
Tab. XXXV. fig. 1. from drawings by Professor Bailey; a. portion of a filament ; h. transverse view ; c. sporangia highly magnified
SPH.EROZOSMA, Corda.
3. S. lamelliferum (Corda).
Sphcerozosma lamelliferum, Corda, Ohserv. Microscop. sur les Animalc. de Carlshad, p. 21. t. 4. f. 29 (1840).
Carlsbad, Corda.
" Chaines courtes, les membres doubles presque uniformes ; un tiers est decoupe transversalement des deux cotes ; lobes rapproches I'un de 1' autre, arrondis ; cuirasse unie, transparente et blanche. Le membre de reunion feuillete, blanc." — Corda, I. c.
BRITISH DESMIDIEiE. 209
4. S. pulchrum (Bailey) ; joints twice as broad as long, deeply incised on each side ; junction-margins straight, connected by shorthands.
Sphcerozosma p^dchrum, Bailey, in lit. cum icone (1847). West Point, New York ; and Princeton, New Jersey, Bailey.
Professor Bailey informs me that this species is tmce as large as Sphce- rozosma vertehratum. His figure represents the filament diminishing and increasing in breadth at intervals, an appearance probably caused by the twisting of the plant. Sphcerozosma pulchrum agrees with ^S". vertehratum in the presence of a mucous tube, and also in the form of the joints ; but not in the mode of their connexion with each other. It diflFers from Corda's figure of S. lamelliferum, inasmuch as its segments are not reniform.
Tab. XXXV. fig. 2. a. portion of a filament ; b. joints with mucous tube, from drawings by Professor Bailey.
5. S.} Jili/orme (Ehr.) ; joints bilobed, united by double slender pro- cesses which inclose a quadrate foramen between each pair.
Odontellal Jiliformis, Ehrenberg, Infusor. p. 154 (1838); Meteorp. t. 1.
f. 20. Tessarthra filiformis, Ehrenberg, Infusor. t. 10. f. 21 (1838). Isthmia Jiliformis, Meneghini, Synop. Desmid. in Linncea 1840, p. 205. Isthmosira filiformis, Kiitzmg, Phycologia Germanica, p. 141 (1845).
Germany, 'Ehrenberg, Kutzing.
MICRASTERIAS, Ag.
14. M. apiculata (Ehr.) ; frond orbicular, rough with scattered spines; segments five-lobed, lobes incised and toothed, end lobe narrow.
Euastrum apiculatum, Ehrenberg, Abh. der Berl. Ak. 1833, p. 245; In- fusor. p. 167. Kiitzmg, Phyc. Germ. p. 134.
Euastrum aculeatum, Ehrenberg, Infus. t. 12. f. 2 (1838).
Micrasterias apiculata, Meneghini, Synop. Desmid. in Linncea 1840, p. 216. Brebisson, in lit. cum specimine.
Germany, Ehrenberg. Falaise, Brebisson.
Specimens sent me by M. de Brebisson have deeper incisions than that figured by Ehrenberg, and are also smaller.
15. ilf. quadragies-cuspidata (Corda) ; frond with scattered hair-like spines ; end lobe the broadest.
Cosmarium quadragies-cuspidatum, Corda, Observ. Microscop. sur les Ani- malc. de Carlsbad, p. 30. t. 6. f. 40 (1840).
Carlsbad, Corda.
This plant bears the same relation to Micrasterias apiculata which M. crenata and M. truncata bear to M. denticulata and ISI. rotata. I subjoin the following description from Corda's work : —
210 BRITISH DESMIDIE.E.
" Corpuscules chevelus, verts, presque a six lobes. Lobe du milieu trian- gulaire, les coins exterieurs a deux pointes ; au milieu, deux cylindres vert fonce, appuyes I'un centre I'autre. Chaque lobe lateral a trois decoupures, et chaque decoupure a deux dents."
16. M. foliacea (Bailey); frond subquadrate ; end lobes narrow, with emarginate angles ; lateral lobes inciso-dentate, with a short rounded tooth-like projection next the end lobe.
Micrasterias foliacea, Bailey, in lit. cum icone (1847). "Worden's Pond, Rhode Island, Bailey.
" Frond small, smooth, nearly quadrangular in the general outline : seg- ments composed of three principal lobes, of which the middle one is nearly simple and emarginate : the lateral lobes are incised, in much the same manner as in Micrasterias rotata, and all their subdivisions extend to an equal distance from the middle line of the frond." — Bailey, in lit.
Tab. XXXV. fig. 3. Frond di\dding, from a drawing by Professor Bailey.
17. M. Turreyi (Bailey); frond orbicular; lateral lobes deeply in- cised; inner subdivisions acute, external bidentate at the apex, all tapering.
Micrasterias Torreyi, Bailey, in lit. cum icone (1847). Near Princeton, New Jersey, Bailey.
This species connects the elliptic with the orbicular species. The end lobe is narrow and not exserted ; the angles taper into acute points or spines. All the incisions are deep. The lateral lobes have five subdivisions, two belonging to the basal lobe and three to the intermediate ; but the distinction is obscure, and only indicated by the rather deeper incision which parts them. Of the subdivisions, that next the other segment and that adjacent to the end lobe are bidentate at the apex, the rest taper gradually into acute points.
Tab. XXXV. fig. 5. Frond from a drawing by Professor Bailey.
1 8. M. muricata (Bailey) ; " segments divided by deep indentations into three transverse portions ; the basal with three linear processes on each side, the others with two on each side."
Euastrum muricatum, Bailey, American Journal of Science and Arts, 1846, p. 126. figs. 1, 2.
Catskill Mountains, United States, Bailey.
Micrasterias muricata belongs to the same section as M.furcata, but differs from that and every other known species in some remarkable par- ticulars. The division into five lobes is indicated merely by the presence of processes, which, unlike those in the other species, do not diverge in the front view, but spread laterally, in such a manner that the one nearest the eye more or less conceals its companions.
BRITISH OESMIDIK.K. 211
19. M. Baileyi ; frond granulated ; segments three-lobed ; lobes
bipartite, end one much-exserted.
Micrasterias, n. sp., Bailey, in lit. cumicone (1846). West Point, New York ; and Rhode Island, Baileij.
Micrasferias Baileyi is allied to M. furcata and M. Crvx-Melitensis ; the frond however is minutely granulate, the segments are only three-lobed, and the end lobe is moreexserted than it is in those species. The basal lobes are deeply bipartite, the end one merely sinuated. All the subdivisions are bi- dentate at the apex.
Tab. XXXV. fig. 4. Empty frond : from a drawing by Professor Bailey.
20. M. incisa (Kiitz.); lobes horizontal, basal ones truncate, with a tooth at each angle ; end lobe convex, its angles acute.
Euastrum Cmx-Melitensis, Ehrenberg, Infus. t. 12. f. 3 c. (1838). Eiiastrum incisum, Brebisson, Meneghini, Synop. Desmid. in LinncBa 1840,
p. 216. Kiitzing, Phyc. Germ. p. 134. Micrasferias incisa, Brebisson, in lit. (1846).
Germany, Ehrenberg . Falaise, Brebisson.
EUASTRUM, Ehr.
19. E. cornutum (Kiitz.); segments three-lobed; terminal lobe cu- neate, included between two process-like projections of the basal portion.
Euastrum cornutum, Kiitzing, Phycologia Germanica, p. 135 (1845) ; in lit. cum icone.
Germany, Kiitzing.
The frond resembles that of Euastrum crassum, but the outer angles of the basal portion of each segment are prolonged into rostrate-like processes which include the terminal lobe between them.
Tab. XXXV. fig. 13. Frond : from a drawing by Professor Kiitzing.
20. E. Pelta (Corda) ; segments quadrangular ; end margin with a rounded protuberance at each corner ; lateral margins with a small protuberance at the basal end and a larger one near the outer end.
Cosmarium Pelta, Corda, Almanack de Carlsbad 1835, p. 121. t. 2. f. 25.
Meneghini, Synop. Desmid. in Linncea 1840, p. 222. Euastrum Pelta, Kiitzing, Phycologia Germanica, p. 135 (1845).
Carlsbad, Corda.
21. E. creuatum (Kiitzing).
Euastrum crenatum, Kutzing, Phycologia Germanica, p. 135 (1845). Dalmatia, Kiitzing.
This plant may be a variety of Euastrum elegans. Tab. XXXV. fig. 14. Frond: from a drawing by Professor Kiitzing.
p
212 BRITISH DESMlDIFiE.
22. E. crennlatum (Ehr.).
Euastrum crenulatum, Ehrenberg, Meteorp. t. 1. f. IG. Kiitzing, Phyco- logia Germanica, p. 135.
Germany, Ehrenberg.
I am unacquainted with the characters of this species.
COSxMARIUxM, Corda.
34. C. Palangula (Breb.).
Cosmarium Palangula, Brebisson, in lit. cum icone (1846). Falaise, JBrebisson.
M. de Brebisson informs me that " Le Cosmarium Palangula me semble se distinguer du Cos. Cucurbita par sa forme plus cylindrique, tronquee et non en Courge, ses scries de points plus fines, transverses et non longitudinales." I am hoAvever unable to distinguish this species from C. Cucurbita, for the puncta are scattered in British specimens of the latter.
35. C. lagenarium (Corda) ; segments triangular, all the angles broadly rounded.
Cosmarium lagenarium, Corda, Aim. de Carlsbad 1835, p. 121. t. 2. f. 26. Brebisson, in lit.
Carlsbad, Corda.
36. C. Papilio (Menegh.) ; segments smooth, triangular, with rectan- gular apex ; end view linear, with a lobe at the middle of each side.
Cosmarium Papilio, Meneghini, Consp. Alg. Eugan. p. 18 (1837) ; Synop. Desmid. in Linn(Ba 1840, p. 223.
Italy, Meneghini.
37. C. ventricosum (Kiitz.).
C. ventricosum, Kiitzing, Phycologia Germanica, p. 136 (1845) ; in lit. cum icone.
I believe this to be a species of Cosmarium in a dividing state.
XANTHIDIUM, Ehr.
7. X. Artiscon (Ehr.) ; segments narrowed at the base ; end margin with numerous elongated spines which are divided at the apex.
Xanthidium, No. 2, Bailey, A^nerican Journal of Science and Arts, v. 41.
p. 291. t. 1. f. 15 (1841). Xanthidium Artiscon, Ehrenberg, Verbreitung und Einjluss des Mikrosko-
pischen Lebens in Sud- und Nord-Amerika (1843).
West Point, New York, Bailey.
BRITISH DESMIDIE.K. 213
XautkiJmm Artiscon differs from A', armatvvi by its segments tapering at the base : its spines also are much longer and are more restricted to the outer and rounded margin.
Several plants referred by Ehrenberg to Xanthidium are angular in the end view, and properly belong to Staurastrum.
8. X. furcatum (Ehr.) ; " corpuscules globose, green, single orbinate, spinous ; spines scattered, forked at the apex."
Xanthidium furcatum, Ehrenberg, Infus. p. 148. t. 10. f. 25 (1838) ; Meteor]), t. 1. f. 21.
This plant is probably a Staurastrvm. M. de Brebisson refers it to S. spivosum, and Professor Kiitzing makes it a synonym of his Thycastrvm fur- cigerum (JDidymocladon furcigerus) . Of neither have I seen specimens re- sembling Ehrenberg's figure, from which indeed I believe the latter plant is very distinct.
ARTHRODESMUS, Ehr.
3. A. minutus (Kiitz.).
Euastrum Incus, Kiitzing, Phycologia Germanica, p. 137 (1845) ; (not
Staurastrum Incus, Meneghini). Euastrum minutum, Kiitzing, in lit. cum icone (1846). Arthrodesmus minutus, Brebisson, in lit. (1846).
Germany, Kiitzing.
Tab. XXXV. fig. 15. a, h. perfect fronds ; c. dividing frond : from drawings by Professor Kiitzing.
4. A. ? truncatus (Ehr.) ; " corpuscules green, slightly compressed, campanulate, geminate, externally truncate, spinous/'
Arthrodesmus truncatus, Ehrenberg, Infus. p. 152 (1838).
This plant is probably either a Xanthidium or a Staurastrum.
STAURASTRUM, Meyen.
39. S. pygwKEum {Qr&h.) ', segments cuneiform; end view triangular, with slightly rounded sides.
Staurastrum pygmceum, Brebisson, in lit. cum icone (1846). Falaise, Brebisson.
Staurastrum pygmcBum is smaller than S. alternans, its sides, in the end view, are more convex, and its angles less rounded. The sporangium is or- bicular and spinous.
Tab. XXXV. fig. 26. from drawings by M. de Brebisson: a. front view of frond ; b. immature sporangium ; c. mature sporangium.
p2
214 BRITISH DESMIDIEjC.
40. S. rugulosum (Breb.) ; segments elliptic, denticulate at their sides ; end view triangular, with the angles broadly rounded and denticulate.
Euastrum, No. 9, Bailey, American Journ. of Science and Arts, v. 41. p. 296.
t. l.f. 9 (1841). Staurastrum rug%dosi(m, Brebisson, in lit. cum icone (1846).
West Point, New York, Bailey. Falaise, Brebisson.
Tab. XXXV. fig. 19. from drawings by M. de Bre'bisson : a. front view; b. end vicAv.
41. S. scabrum (Breb.); segments elliptic, scabrous; end view tri- angular, fringed with minute emarginate spines.
Sfaurastrum scabrum, Brebisson, m lit. cum icone (1846). Falaise, Brebisson.
Tab. XXXV. fig. 20. from drawings by M. de Brebisson : a. front view ; b. end A-iew.
42. S. bacillare (Breb.) ; frond smooth ; processes capitate ; end view with three to five capitate rays or processes.
Binatella bacillaris, Brebisson, Alg. Fal. p. 66 (1835). Staurastrum bacillare, Breb., Meneghini, Synop. Desmid. in Linneea 1840, p. 228. Brebisson, in lit. cum icone.
Falaise, Brebisson.
Frond smooth ; processes in front view stout, divergent, each terminated by a round knob ; end view three- to five-rayed, the rays capitate in the same manner as in the front view.
A remai'kable and very distinct species.
Tab. XXXV. fig. 21. from drawings by M. de Brebisson : a. front ^-iew of frond ; b, c, d. transverse views.
4.3. S. Capitulum (Breb.) ; segments quadrate, sinuated on each side, prominences rough ; end view triangular, with broadly rounded angles.
Staurastrum Capitulum, Brebisson, in lit. cum icone (1836). Falaise, Brebisson.
Frond quadrilateral, nearly twice as long as broad ; constriction shallow ; the segments have two rounded prominences on each side and a small semi- circular sinus between them ; these prominences are rough with minute gra- nules, which give them a crenate appearance. End margin straight. End view triangular, the angles broadly rounded ; sides nearly straight, bat each slightly constricted at the middle.
Tab. XXXV. fig. 25. from drawings by M. de Brebisson : a. front view of frond ; 6. end view.
BRITISH DESMIDIE.H. 215
44. S. pileolatum (Breb.) ; frond quadrilateral, slightly constricted at the middle ; segments terminated by three conical processes.
Statirastrum pileolatum, Brebisson, in lit. cum icone (1846). Falaise, Brebisson.
Frond twice as long as broad ; segments quadrate, with a broad, shallow sinus on each side ; the end terminated by three conspicuous conical pro- cesses, which are rough with minute granules. End view triangular, the angles roimded.
Tab. XXXV. fig. 22. from drawings by M. de Brebisson : a. front view of frond ; b. end view.
45. S. echinatum (Breb.).
Staurastriim echinatum, Brebisson, in lit. cum icone (1846). Falaise, Brebisson.
This species appears, from M. de Brebisson' s drawings, to be closely allied to Staurastnan hirsutum and S. teliferum.
Tab. XXXV. fig. 24. from drawings by M. de Brebisson : a. front \'iew of frond ; b. end view.
46. 8. crenatum ; segments cuneate ; outer margins crenate ;
end view with three truncate and crenate angles.
Staurastrum, new sp., Bailey, in lit. cum icone (1847).
Rhode Island, Bailey.
Tab. XXXV. fig. 17. a. front view of frond; b. end view : from drawings by Professor Bailey.
47. S' bifidum (Ehr.); frond smooth; end view with three cloven angles.
Desmidium bifidum, Ehr. Abh. der Berlin Ah. 1832, p. 292 ; Infusor. p. 141.
t. 10. f. 11. Phycastrum bifidum, Kiitzing, Phycologia Germanica, p. 138 (1845). Staurastrum bifidum, Brebisson, in lit. (1846).
Germany, Ehrenberg .
48. S. eustephanum (Ehr.) ; end view triangular with six emarginate spines on the upper surface ; each angle terminated by a short ray tipped with spines.
Desmidium eustephanum, Ehrenberg, Ferbr. und Einfiuss des Mikrosk. Lebens in Sud- und Nord-Amerika, t. 4. f 23 (1843).
West Point, New York, Bailey.
216 BRITISH DESMIDIE^.
49. S. senarium, Ehr.
Desmidium senarium, Ehrenberg, Verhr. und Einfluss des MiJcrosk. Lehens in Sud- und Nord-Amerika, t. 4. f. 22 (1843).
West Point, New York, Bailey.
Ehrenberg's figure represents tbe end view as triangular, the angles termi- natino- iu short rays, which are tipped by minute spines : on each side are two short forked spines, and six others on the upper surface. His figure agrees in some respects with Staurastrum spinosum, consequently S. senarium may prove a variety of that very variable species.
50. S, Ehrenbergii, Corda.
Xanthidium Ehrenbergii, Corda, Observ. Microscopiques sur les Animalcules de Carlsbad, p. 29. t. 5. f. 36, 37 (1840).
Prague, Corda.
" Corpuscules par paire, vus de cote, ovales ; vus d'en haut, triangulaires, munis de six appendices terminaux et lateraux, et de deux autres appendices centraux, qui sont courts, blancs, en fourchette, mais a pointes divergentes." — Corda, I. c.
Corda' s figure of the front view resembles Staurastrum spinosum.
51. S. articulatum, Corda.
Xanthidium articulatum, Corda, Observ. Microscopiques sur les Animalcules de Carlsbad, p. 28. t. 5. f. 35 (1840).
Carlsbad, Prague and Reichenberg, Corda.
" Corpuscules ovales, par paire, munis a\ix deux bouts d'un appendice a deux cellules, qui se divise encore en forme de fourchette ; et lateralement en deux appendices plus longs a quatre cellules, et mie pointe en fourchette. Sur les deux cote's plats, se trouvent deux protuberances transversales, e'galement pourvues de deux allongements cellulaires en fourchette." — Corda, /. c.
52. S. coronatum (Ehr.); end view triangular and terminating at each angle in three short, diverging arms which are divided at the apex.
Xanthidium, No. 3, Bailey, American Journ. of Science and Arts, v. 41,
p. 291. t. 1. f. 16 (1841). Xanthidium coronatum, Ehrenberg, Verhr. und Einfluss des Mikrosk. Lebens
in Slid- und Nord-Amerika, t. 4. f. 26 (1843).
"West Point, New York, Bailey.
Professor Bailey's figure, which in a list of American Desmidiete obligingly connaunicated he refers to as Xanthidium coronatum, Ehr., in the front view resembles Xanthidium Artiscon, whilst Ehrenberg's appears to me a good representation of the front view oi Bidymocladon furcigerus. I doubt there- fore whether these two figures can represent the same species.
BRITISH UESMIDIE^. 217
53. S.} tninus (Kiitz.) ; frond smooth; end view with five slender
acute rays.
Pentasterias minor, Kiitzing, Phycoloyia Generalis, p. 162 (1843). Phycastrumi minus, Kiitzing, Phycologia Gennanico, p. 139 (1845) ; in lit. cum icone.
Nordhauseu, Prussia, Kiitzing.
Tab. XXXY. fig. 18. a, b. Fronds : from drawings by Professor Kiitzing.
54. S. glabrum (Ehr.) ; frond smooth ; end view triangular, each angle terminated by a mucro-like spine.
Euastrum, No. 14, Baileif, Amer. Journ. of Science and Arts, v. 41, p. 297.
t. l.f. 14 (1841). Desmidium glabrum, Ehrenberg, Verbreitung und Einfluss des Mikrosk.Lebens
in Slid- und Nord-Amerika (1843) ; Meteor]^, t. l.f. 3. Phy cast rum glabrum, Kiitzing, Phycologia Germanica, p. 137 (1845).
West Point, New York, Bailey. Germany, Ehrenberg. This species is probably identical with Staurastrum Avicula.
55. S. granulosum {FAiY.).
Desmidium granulosum, Ehrenberg, Meteorp. t. 1. f. 12.
Phycastrum gramdosum, Kiitzing, Phycologia Germanica, p. 138 (1845).
Germany, Ehrenberg .
This species is known to me only by name.
56. S. globulatum (Breb.) ; segments fusiform, capitate ; end view
lar, each angle terminated by a granulated knob.
Staurastrum globulatum, Brebisson, in lit. cum icone (1846).
Falaise, Brebisson.
Tab. XXXV. fig. 23. a. end view of frond ; b. front view : from drawings by M. de Brebisson.
DOCIDIUM, Breb.
8. D. coronatum (Breb.) ; frond stout ; suture projecting on each side ; segments inflated at the base and bordered by tubercles at the end.
Docidium coronatum, BrebissoQ, in lit. cum icone (1846).
Falaise, Brebisson.
This species agrees with Docidium nodulosum not only in size and form, but in having a suture projecting on each side, and also in its segments, which have undulated margins ; but it is distinguished from that plant by having the ends bordered Avith minute but distinct tubercles. The end view is cir- cular, the margin crenate. Docidium coronatum differs from D. Ehrenbergii in its larger size and projecting suture.
218 BRITISH DESMIDIE^.
Tab. XXXV. tig. 6. a. empty segment ; b. end view : from drawings by M. de Brebisson.
9. D. nodosum (Bailey) ; frond stout ; segments with four prominent nodes separated by constrictions ; end view crenate.
Clusteriwn nodosum, Bailey, Amer. Journ. of Science and Arts, 1846, v. 1.
p. 1 27. f. 3. Docidmm nodosum, Bailey, in lit. cum icone (1847).
United States, Bailer/.
An end view shows that each node is not a simple swelling, but really formed by whorls of tubercles.
" This species is easily recognised by the deep indentations in its outline, corresponduig to the constrictions which separate the transverse rows of knot- like projections. It is one of the largest species in the genus." — Bailey, I. c.
Tab. XXXV. fig. 8. a. empty segment ; b. end view : from dravdngs by Professor Bailey.
10. D. constrictum (Bailey) ; frond stout; segments with moderately deep constrictions, which separate four equal, gently curving pro- minences ; end view entire.
JDocidium constrictum, Bailey, in lit. cum icone (1847). Worden's Pond, Rhode Island, Bailey.
" This species is at once distinguished from Docidium nodosum by the cross section of the nodes being a simple circle instead of an indented one." — Bailey, in lit.
Tab. XXXV. fig. 7. from drawings by Professor Bailey : a. front view ; b. end view.
11. D. verrucosum (Bailey) ; segments with numerous whorls of small prominences which give the margins an undulated appear- ance, all the undulations equal.
Closterium verrucosum, Bailey, American Journal of Science and Arts, 1 846, V. 1. p. 127. f. 4.
New York ; Rhode Island, Bailey.
" This is a very pretty species with a waved outline, caused by the slight projections, which are arranged in numerous transverse rings." — Bailey, /. c.
12. D. verticillatum (Bailey) ; segments with numerous whorls of tooth-like projections ; ends with three bidentate processes.
Docidium vei'ticillatum, Bailey, in lit. cum icone (1847). Triploceras verticillatum, Bailey, in lit. (1847).
Worden's Pond, Rhode Island ; Princeton, New Jersey, Bailey.
BRITISH DESMIDIE^. 219
A most remarkable and interesting plant, for a specimen of which I am indebted to Professor Bailey.
The triple terminal processes are so milike what we find in other species of Docidhun, that Professor Bailey, in a letter to me, proposes to form a new genus for the reception of this plant.
Tab. XXXV. fig. 9. a. empty frond ; b, c. empty segments ; d, e. extre- mities highly magnified : from drawings by Professor Bailey.
13. D. crenulatum (Ehr.).
Closterium crenulatum, Ehrenberg, Verbreitung und Einfluss des Mikrosk. Lebens in Sud- und Nord-Amerika (1843).
Professor Bailey informs me that this plant is identical with Bocidium no- didostim.
CLOSTERIUM, Nitzsch.
23. C. cuspidatum (Bailey) ; frond smooth, crescent-shaped ; ends mucronate.
Closterium cuspidatum, Bailey, in lit. cum icone (1847). Worden's Pond, Rhode Island, Bailey.
Closterium cuspidatum differs from every other species of the genus in having each end tipped by a spine or mucro. Tab. XXXV. fig. 1 1 . Frond : from a drawing by Professor Bailey.
24. C. Cucumis (Ehr.); frond smooth, stout, semilunate ; ends broadly rounded.
Closterium Cucumis, Ehrenberg, Verbreitung und Einfluss des Mikrosk. Lebens in sad- und Nord-Amerika, t. 4. f. 29 (1843).
New York, Bailey.
Ehrenberg' s figure represents this species about five times longer than broad, in form resembling Closterium Lunula, but stouter in proportion to its length, and having more rounded ends.
25. C. Thureti (Breb.) ; frond smooth, crescent-shaped; ends sub- acute ; margins unconnected at the suture ; vesicles in a single series.
Closterium Thureti, Brebisson, in lit. cum icone (1846). Falaise, Brebisson.
26. C. arcuatum (Breb.) ; frond smooth, slender-crescent-shaped ; ends obtuse, scarcely notched.
Closterium arcuatum, Bre'bisson, in lit. cum icone (1845).
220 BRITISH DESMIUIEJE.
Closterium acuminatum, Kiitzmg, Phycologia Gennanica, p. 130 (1845), (according to Kiitzing in Hi.).
Falaise, Brebisson. Germany, Kiitzing.
I am miable to distinguish Closterium arcuatum from C. DiancB ; but in drawings sent me by M. de Brebisson, the latter has distinct terminal notches, which are wanting in the former.
27. C. Venus (Kiitz.).
Closterium Venus, Kiitzing, Phycologia Germanica, p. 130 (1845) ; in lit. cum icone.
Germany, Kiitzing.
I am indebted to Professor Kiitzing' s kindness for a drawing of this species, but I must confess that I am unable to discover any characters sufficient to distingmsh it from Closterium Biance.
Tab. XXXV. fig. 12. Frond, from a drawing by Professor Kiitzing.
28. C. Amblyonema (Ehr.) ; frond stout, linear, slightly curved, twenty times longer than broad ; ends rounded.
Closterium lineatum, Bailey, American Journ. of Science and Arts, v. 4 1 .
p. 303. t. l.f. 34 (1841).? Closterium Amblyonema, Ehrenberg, Verbreitung und Einjluss des Mikrosk.
Lebens in Slid- und Nord-Amerika (1843).
"West Point, New York, Bailey.
29. C. uncinatum (Kiitz.) ; frond slender, finely and closely striated; extremities tapering to a subacute point and suddenly curved downwards.
Closterium uncinatum, Kiitzing, Phycologia Germanica, p. 131 (1845) ; in lit. cum icone,
Germany, Kiitzing.
30. C decus,<iatum (Kiitz.) ; frond stout, finely and closely striated,
slightly curved, gradually tapering ; extremities slender, but obtuse
at the apex.
Closterium decussatum, Kiitzing, Phycologia Germanica, p. 131 (1845) ; in lit. cum icone.
Germany, Kutzing.
A drawing sent me by Professor Kiitzing represents the strise as regularly crossing each other, so as to form diamond-shaped reticulations. As this appearance is not unusual in dried specimens, when the flattened frond permits the strife of both surfaces to be visible together, I will venture to suggest the possibility that Professor Kiitzing's drawing may have been taken from a frond in that condition. Closterium decussatum seems to differ from C. tur- gidwii in its more tapering cNtremitics.
BRITISH UESMIDIE.«. 221
31. C. turgidulum {Kutz.) ; frond stout, curved ; extremities slender, gradually tapering ; strias few, conspicuous.
Clostermm turgidulum, Kiitzing, Phycologia Germanica, p. 132 (1845); in lit. cum icone.
Germany, Kiitzing.
Closterium turgidulum differs fioni C. costatum in its more elongated ex- tremities.
32. C. obtusangulum (Corda).
Closterium obtusangulum, Corda, Observations Microscop. sur les Animalc. de Carlsbad, p. 35. t. tJ. f. 42 (1840).
Carlsbad, Corda.
" Corps courbe en croissant, quadrangulaire ; coins ronds. Cuirasse miie, blanche, arrondie vers les pointes, et transparente ; au milieu un ruban trans- versal e'troit, blanc et transparent. Pas de ve'sicules rotatoires dans les pointes, mais beaucoup de corpuscules rotatoires, ovales, transparents, blancs, se mouvant vivement." — Corda, I. c.
33. C. incequale (Ehr.) ; minute, semilunate ; extremities unequal, conic, ends acute ; striae prominent ; vesicles scattered.
Closterium incecfiale, Ehrenberg, Abh. der Berlin Ak. 1831, p. 67; Infus. p. 98. t. 6. f. 11. Meneghini, Si/noj}sis Desmid. in LinncBa 1840, p. 235. Kiitzing, Phycologia Germanica, p. 131.
Germany, Ehrenberg, Kiitzing.
34. C. quadrangidare (Corda).
Closterium quadrangidare, Corda, Observations Mici'oscop. sur les Animalc. de Carlsbad, p. 35. t. 6. f. 46 (1840).
Carlsbad ; Reichenberg, Corda.
" Long, corps mince, quadrangulaire. Coins aigus. Cuirasse unie, trans- parente, blanclie. Substance interne vert fonce, a petits grains. Sur les pointes les quatre surfaces de la cuirasse sont obliquement coupe'es, et la pointe arrondie. EUe contient de grosses ve'sicules rotatoires, bien limitees, d'un rouge pale, avec plusieurs corpuscules rotatoires elliptiques et rougeatres." — Corda, I. c.
35. C. gracile (Breb.) ; frond slender, smooth, lanceolate, gradually tapering into short beaks, which are curved downwards.
Closterium gracile, Brebisson, Meneghini, Synop. Desmid. in Linncea 1840,
p. 234, under C. lineatum. Staurocerus gracile, Brebisson, in lit. cum icone (1846).
Falaise, Brebisson.
222 BRITISH DESMIDIE.E.
Clostei'ium yracile differs from the other rostrate species in its smooth frond. Its beaks are shorter than those of C. rostratum and C. set ace urn, and its frond is less inflated.
36. C. tenerrimum (Kiitz.).
Closterium tenerrimum, Kiitzing, Phycologia Germanica, p. 130 (1845); in lit. cum icone.
Nordhausen, Kiitzing.
I can perceive in Professor Kiitzing' s drawing no character by which this plant can be separated from Closterium acutum.
Tab. XXXV. fig. 10. Fronds : from a drawing by Professor Kiitzing.
ANKISTRODESMUS, Corda.
2. A. fusiformis (Corda).
Ankistrodesmus fusiformis, Corda, Almanack de Carlsbad 1838, p. 199. t. 2. f. 18. Carlsbad, Corda.
3. A. convolutus (Corda).
Ankistrodesmus convolutus, Corda, Almanack de Carlsbad 1838, p. 199. t. 2. f. 19. Carlsbad, Corda.
I am unacquainted with the characters of these species.
SCENEDESMUS, Meyen.
7. S. antennatus (Breb.) ; cells fusiform, somewhat ventricose at the middle ; ends cuspidate, each terminated by a minute orbicular globule.
Scenedesmus antennatus, Brebisson, in lit. cum icone (1846). Falaise, Brebisson.
Scenedesmus antennatus resembles S. obliquus in form, and also in the arraiigement of its cells ; but it is distinguished from that and every other species by having the attenuated points tipped by minute globules.
Tab. XXXV. fig. 27. a, b. different states of frond : from drawings by M. de Brebisson.
INDEX.
The names printed in inalics are synonyms.
Page
Achnanthes.
dbnorpha, Turpin . 191 obliqua, Turpin ... 192 octalterna, Tuqjin 19.3 quadralterna, Turp. 193 quadricauda, Turp. 190 quadrijuga, Turpin 190
Ankistrodesmus, 179, 205
convolutus 222
falcatus 180
fusiformis 222
gregariuSf^rih. ... 180
Aptogonum 63, 196
Baileyi 208
Desmidiuui 64
Arthrodesmus ... 117,200
acutus,^h.x 191
acutus, Bailey 193
convergens 118
cylindriciis, Ehr.... 57
Incus 118
minutus 213
octocornis, Ehr. ... 116 pectinatus, Ehr. ... 191 quadricaudatus, YAir. 190 ? truncatus 213
Bacillarla.
Lunula, Schrank... 163
Bambusina.
Brebissonii,Kutz.. 59
Binatella.
aculeata, Breb. ... 113 bacillaris, Breh. ... 214
hispida, Breh 127
muricata, Breb. ... 126 muticum, Breb. ... 125 tricornis, Breb. ... 134 tricuspidata, Breb. 122 tumida, Brel) 126
Closterium 159, 204
acerosum 1 64
acuminatum, Kiitz. 220
Acus, Nitzsch 175
acutuni 177
Amblyonema 220
angustatum 172
ai'cuatum , 219
Page
attenuatum 169
Baculum, Breb. ... 158 Baillyanum, Br^b. . 169 £re6is5o?ji j.Menegh. 145 caudutum, Corda... 175 clandestinum,Kutz. 109
Cornu 176
costatum 170
crenulatum, Ehr.... 219
Cucumis 219
curtum, Breb 109
cuspidatum 219
Cylindrocystis,Ktz. 153 Cylindrus, Ehr. ... 150
decussatum 220
Dianae 168
didymotocum 168
Digitus, Ehr 151
dilatatum, Kiitz 170
doliolatum, Breb... 170
Ehrenbergii 166
elongatum, Breb.... 173 falcatvm, Menegh. 180
gracile 221
granulatum, Breh.. 147 gregarium,Menegh. 180
insequale 221
intermedium 171
Jenneri 167
juncidum 1 72
l(Bve, Kiitz 146
lamellosum, Breb. . 151
lanceolatum 164
Leibleinii 167
lineatum 173
lineatum, Bailey ... 220
Lunula 163
Lunula, Kiitz 166
Lumila,lje\h\ 167
margaritaceum,^hr. 149
monile, Kiitz 145
moniliferura 166
nodosum, Bailey ... 218
obtusanguliun 221
quadrangulare 22 1
Ralfsii 174
rostratum 175
rostratum,'R,2\h... 174 rostratum, B&iley .. 176
ruficeps, Ehr 168
Sceptrum, Kiitz.... 158
setaceum 176
striolatum 170
subrectum, Breb.... 169 sulcatum, Breh. ... 172
tenerrimum 222
tenue, Kiitz 176
tenue, Bailey 165
Thureti 219
Trabecula, Ehr. ... 157 TraiecwZa, Bailey. . 155 trabeculoides,Corda. 158 truncatum, Breb.... 156 truncatum,K.iitz... 156
turgidulum 221
turgidum 1 65
uncinatum 220
Venus 220
verrucosum, Bailey 218
Conferva.
dissiliens. Smith... 51 mucosa, Mertens... 53
Cosmarium 91, 198
aculeatum, Menegh. 1 13
amcenum 102
antilopcBum, Br&o. . 114 armatum, Breb. ... 112
attenuatum 110
binale, Menegh. ... 90
bioculatum 95
bioculatum, Menegh. 96
biretura 102
Botrytis 99
Brebissonii 100
Broomeii 103
ca;latum 103
commissurale 105
connatum 108
conspersum 101
crassu7n,Breh 81
crenatum 96
cristatum 105
Cucumis 93
Cucumis, Ralfs 93
224
INDEX.
Page
Cucurbita 108
curtum 109
cyliudricum 106
deltoides, Corda ... 99 Bidelta, Menegh. . 84
elegans, Breb 89
gemm,atuin,^Yeh.... 87
granatum 96
Incus, Breb 118
lagenarium 212
margaritiferum ... 100
Meneghinii 96
moniliforme 107
oblongum, Breb. ... 80
orbiculatum 107
ornatum 104
ovale 98
ovale, Jenner 98
Palangula 212
palmatum,^x&a. ... 116
Papilio 212
pectinaium, Breb. . S6
Pelta, Corda 211
Phaseolus 106
pyramidatura 94
quadragies - cuspi- datum, Corda ... 209
quadratum 92
Ralfsii 93
sinuosum, Corda... 80 Sportella, BreT). ... 104 tetraophthalmum . . 98
Thwaitesii 109
tinctiim 95
^rMwcff/Mm, Corda.. 75
turgidum 110
undulatum 97
ventricosum 212
verrucosum,Menegh. 79
Cy Jin drocystis .
Brebissonii,Menegh . 1 5.3 truncata, Breb. ... 152
Cymbella. Hopkirkii, Moore . . 1 64 Icctevirens, Harvey 153 reniformis, Ag. ... 100
Desmidium 60, 196
acvleatum, Ehr. ... 142 apiculosum, Ehr.... 126 apto^onum, Breb. . . 64
bijidum, Ehr 215
bifip'mosum, Corda . xix
Borreri, Ralfs 58
comjjressvm, Ralfs . 65 compressum, Corda 57 cylindricum,Gveville 57
didymum 207
eustephamim,^hr. . 215
glabrum, Ehr 217
granulosum, Ehr... 217 hexaceros, Ehr. ... 134
limbatum,Chauv. .. 51 mucosum, Breb. ... 51 orbicular e, Ehr. ... 125 quadrangulare,KvLtz. 62 quadrangulatum ... 62
ramosum, Ehr 141
senarium, Ehr 216
Swartzii 61
undulatum 207
vertebratum, Breb. 65
Diatoma.
Swartzii, Ag 61
Didymocladon... 144,203 furcigerus 144
Didymoprium 55, 196
Borreri 58
cylindricum, Ralfs . 57 Grevillii 57
Docidium 155, 204
asperum 158
Baculum 158
clavatum 156
constrictum 218
coronatum 217
crenulatum 219
Ehrenbergii 157
minutum 158
nodosum 218
nodulosum 155
truncatum 156
venucosum 218
verticiilatum 218
Echinella.
acuta, Lyngbye ... 1/7 oblonga, Greville... 80 rotata, Greville ... 71
Euastrum 78, 197
aculeatnm, Ehr. ... 209
affine 82
americanum, Ehr. . xix
ampullaceum 83
angulosum, Ehr. ... 99
ansatum 85
apiculatum, Ehr.... 209 armatum, Kiitz. ... 112
binale 90
binale, Kiitz 85
bioculatum, Kiitz. . 96
Botryt is, Ehr 99
carinatum, Ehr. ... 98
circulare 85
convergens, Kiitz. . 118
coruutum 211
crassum 81
crenatum 211
crenulatum 212
Crux-Melitensis,
Ehr 73
cuneatum 90
Didelta 84
eleffans 89
fasciculatum.,Kutz. 114
gemmatum 87
gemmatum, Ralfs... 86 hexagonum, Corda . 183 hirsutum, Kiitz. ... 127
humerosum 82
incisum, Breb 211
Incus, Kiitz 213
insigne 83
integer rimum, Ehr. 93 inter stitiale, Kiitz. xix margaritiferum,
Ehr 100
minutum, Kiitz. ... 213 m?<ncflfMm, Bailey . 210
oblongum 80
octocorne, Kiitz. ... 116 papulosum, Kiitz. . 87
Fecten, Ehr 80
pectinatum 86
Pelta 211
Pe/^a, Ralfs 81
pinnatijidum, Kiitz. 71
pinnatum 81
retusum, Kiitz. ... 118
rostratum 88
Rota, Ehr 70
semiradiatum, Breh. 75 sinuosum., Lenorm. 85
So/, Ehr 72
spinosum, Ralfs ... 89
sublobatum 91
tetraophthalmum,
Kiitz 98
venucosum 79
Etitomia.
oblonga, Harvey ... 80 ro^a^a, Harvey 71
Frustulia.
acuta, Kiitz 177
subulata, Kiitz. ... 177
Gloeoprium.
dissiliens, Birk. ... 52 mucosum, Ralfs ... 53
Goniocystis.
aculeata, Hassall . . 142 aracAmV, H assail... 137 bijidum, Hassall ... 131 dilatatum, Hassall . 133 gracilis, Hassall ... 136 hexaceros, Hassall . 132 Jenneri, Hassall ... 129 margaritacea, Hass. 134 mucronata, Hassall 121 muricata, Hassall . 127 orbicularis, Hassall 125 paradoxum, Hassall 1 38 tetracerum, Hassall 137
Helierella.
Napoleonis, Turpin 186 Boryana, Tm-pin... 187
INDEX.
225
Page
Heterocarpella.
/)inalis,Tinpm i)0
biociilafa, Ikeb. ... 5^5 Botri/tis, Bory ... J>!' Didelta, Tuipin ... S4 tetraophthahna,
Kiitz 98
Ursinella, Kiitz.... 100
Holocystis.
oscitans, Hassall... r^>
Ilyalotheca 51, 196
bambusina, Breb. . . 59 cyUndrica, Elir. ... 57
dissiliens 51
(lubia 207
Grevillii, Breb. ... 57
]\Iertensii,^Yeh 53
mucosa .5.3
mucosa, Kiitz 52
Isthmia. fdiformis, Menegh. 209 rertebrata, Menegh. 65
Istlimosirn. fiUformis, Kiitz.... 209 vertebrata, Kiitz... &^
LiinuUna.
monilif era, ^ory. .. 166 vulgaris, Bory 163
Micrnsterias 68, 197
americana xix
angulosa,¥A\r 187
apiculata 209
]5aileyi 211
Bory 0710, Ehr. ... 187
Boryi, Kiitz 187
Coronula, Ehr. ... 185
crenata 75
Crux-Melitensis ... 73
denticulata 70
elliptica, Ehr 188
falcata, Corda 180
fimbriata 71
foliacea 210
furcata 73
heptactis,'Ejhv 183
incisa 211
Jenueri 76
margoritifero, Ijveh. 100 Melitensis, Ralfs... 73 Melitensis, Menegh. 74
raorsa, Ralfs 74
muricata 210
Napoleonis, Kiitz. . 186 octocornis, Menegh. 116
oscitans 76
papillifera 72
pinnatiiida 77
quadragies - cuspi-
data 209
radiata, HassaU ... 73 radiosa 72
Page Rota, Menegh. ... 70
rotata 71
Rotula, Ehr 183
Sdencea, Kiitz. ... 184 simplex, Kiitz. ... 185 sinuata, Breb. ... 80 Staurastrum, Kiitz. 138 tetracera, Kiitz. ... 137
Tetras, Ehr 182
Torreyi 210
^n'cera, Kiitz 137
tricyclia, Ehr. ... 186 truncata 75
Mulleria.
Lunula, Leclerc . . 163
Odontello.
Desm idium, Ehr 64
jiliformis, Ehr. ... 209 tridentata, Bailey . 208 vnidentata, Ehr. ... 65
Palmella.
cylindrosporo,
liieh 153
Pediastrum 180, 205
angulosum 187
bu-adiatum 1 83
Boryanum 187
Boryanum, Ralfs ... 1 88 constrict urn, HassaW. 188 cruciatum, Kiitz.... 185 elegans, Ilassall ... 184
ellipticnm 188
excavatum, Hassall 186
granulatum 186
Heptactis 183
Hexactis, Hassall . 186 lunare, Hassall ... 184
Napoleonis 186
Napoleonis, Ralfs . 184 Napoleotiis,llassa\\ 185
pertusura 185
i?o^M^«, Kiitz 183
Selena^a 184
simplex 185
simplex, Hassall ... 183
Tetras 182
tricyclium, Hassall 186 vagum, Kiitz 188
Penium 148,203
Brebissonii 153
closterioides 152
curtum, Breb 109
Cylindrus 150
Digitus 150
interruptum 151
Jenneri 153
margaritaceum ... 149 truncatum 1 52
Pentasterias.
margaritacea, Ehr. 134 minor, Kiitz 217
Page
Phycastrum.
aci/Zeafwrn, Kiitz.... 142 apiculosum, Kiitz. . 126
bifid um, Kiitz 215
cuspidatum, Kiitz. 122 dilatatum, Kiitz.... 133 furcigerum, Kiitz. 144 glabrum, Kiitz. ... 217 granulosum, Kiitz. 217 margaritaceum,
Kutz 134
minus, Kiitz 217
mo7iticulosum,ls.utz. 130 orbicidare, Kiitz. . . 125 paradoxum, Kiitz. 138 tricorne, Kiitz. ... 135
Pitkiscus.
angulosus, Kiitz.... 93
Pleurosicyos.
myriopodus, Corda 151
PoJysolenia.
Closterium,YA\r. ... 151
Rkaphidiurn.
duplex, Kiitz 193
fasciculatum, Kiitz. 180
Scenedesmus ... 189, 206
acutus 191
antennatus 222
caudatus, Corda ... 190
dimoi'phus 191
duplex 1 93
/Msi/brm JSjMenegh. 191 heibleinii, Kutz. ... 190 longus, Meyen ... 190 mognus, Meyen ... 190
obliquus 192
obtusus 1 93
octoalternus, Kiitz. 193 pectinafus, Meyen 191 quadralternus, Ku.tz.l93
quadricauda 1 90
quadricaudatus,^hr. 190 triseriatus, Menegh. 192
Schistochilum.
excavatum, Ralfs... 67 unidentatum, Ralfs 66
Selencea.
orbicularis, Nitzsch 184
Spha;rozosma ... 65, 196 elegans, Corda ... 65
excavatum 67
filiforme 209
lamelliferum 208
pulchrum 209
7inidentat:im, Ralfs 66 vertebratum 65
Spirotajnia 178, 205
condensata 179
obscma 179
Staurastrum ... 119, 201 aculeatura 142
226
INDKX.
Page aculeatum, Ka\h ... 142
alternans 132
Arachue 136
aristiferum 123
articulatum 216
asperum 139
Avicula 140
bacillare 214
bifidum 215
bifidum, Ralfs 131
brachiatum 131
brevispina 124
Capitulum 214
controversum 141
convergenSjMenegh. 118
coronatum 216
crenatum 215
cuspidatum 122
cyrtocerum 139
dejectum 121
Dickiei 123
dilatatum 133
echinatum 215
Ehrenbergii 216
enorme 140
eustephanum 215
furcigerum, Breb. . 144
glabrum 217
globulatum 217
gracile 136
granulosum 217
hirsutum 127
Hystrix 128
Incus, Menegli. ... 118
Jenneri, Ralfs 129
Isve 131
lunatum 124
margaritaceum ... 134
Page
minus 217
monticiilosuin 1 30
mucronatum, Ralfs 121
muricatum 126
muricatum, Ralfs ... 127
muticum 125
octocorne, Ralfs ... 116
orbiculare 125
orbiculare, Menegli. 126
paradoxum 138
paradoxum, Ehr.... 137
pileolatum 215
poljmorphum 135
pimctulatum 133
pungens 130
pygmseum 213
quadi'angulare 1 28
rugulosum 214
scabrum 214
senarium 216
sexcostatum 129
spinosum 143
spongiosum 141
teliferum 128
tetracerum 137
tricorne 134
tricorne, Ralfs 132
trilobum, Menegh. 125
tumidum 126
vestitum 143
Stauroceras.
Acus, Kiitz 175
acutum, Breb 1/7
gracile, Breb 221
Ralfsii, Brelj 174
setaceum, Breb. ... 176
stibulatum, Kiitz.... 176
subulatum, Breb. ... 177
Page
Tessarthra. filiformis, Ehr. ... 209 moniliformis, Ehr. 107
Tessarthronia. moniliformis, Tuvp. 107
Tetmemorus 145,203
Brebissonii 145
granulatus 147
Isevis 146
Triploceras. verticillatum,Ba.i\ey 218
Ursinella. margaritifera,Turp. 100
Vibrio.
acerosus, Schrank . 164 Lunula, Miiller ... 163
Xanthidium 111,200
aculeatum 113
aculeatum, Breb.... 113
armatum 112
articulatum, Coi'da 216
Artiscon 212
bisenarium, Ehr. ... 113
Brebissonii 113
coronatum, Ehr. ... 216
cristatum 115
deltoideum, Corda . 126 "idifforme, Ehr. ... 180 Ehrenbergii, Corda 216
fasciculatum 114
fm'catum 213
furcatum, Ralfs ... 112
hirsutum, Ehr 127
octocorne 116
pilosum, Ehr 127
polygonum, Hassall 114 un cinatum, Breb .... 115
THE END.
PRINTED BY RICHARD AND JOHN E. TAYLOR, RED LION COURT, FLEET STREET.
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JI.'./i(/uiatum. 2 £. bi(iHero.->-ii)n. 3J:.i(//7>if. -l-E.iniipuUaceiim . 3E. cirat/are. 6 h. lust que .
E UA S T R U M .
Trtb.XlV^.
/ /: . Duhlla . i^ E. a?isaium . 3 J:, circulare . 4 E. aemynatu ni .' I:. pt'chnnluni . ti ^.rostratiirn . 7E.eIegans. S E.binale.
£.Jenner. <ifl_
COSMAKIUM.
TabX\'.
(•.^filllt^X:''
.9a.
9
EJ^-nn.-.r ,/J.
oS?? ? ° ° ° " ^ O ° ^' ^ ° ° - ^'' o o o 0 o o o 0 0 c o oS ^o'i ^o" ° °^ - - c%°o o c '^ ° ° ° °.°o°.^"V '^ = ° ° o O C C 0 0 c o o o o o o°So°;
IC.quadratum ^ C. Cucuniis o C.Ralfsv. ^C.hyrarnidatwm 5 C.bioculaTurro fj C.Meneqkini 1 C.crenaTum, S CiAnduIatum
BHiU,n,.r sc
COSMAKll'M
T;.l> \V1
^"^M^ ^M^
^>^H^^;^>^^
1 C.Botfj'tis. 2 C.rruayanU.ferum/. 3 C.Jjrebvssortu. 4^ C. conspersurrt-. 5 C . bu^eUt-my . 6C.Broorne^jy 7C.orr(yaMcnv. 8 C. cornnu^surcdc.
JH.Je^Uixf. deZ .
COSMARIUM
Tab XMl
^A, £» " " <i^,
/c.S" - " " vi. Ci° ^ o o Of,
' ;^ O ^ ^"^
2 C ccela.tuni . 2 C.rjristatunv. J C amcerLzirru ^^ C. cxlindri-cum^. 5 C. orbiculahinv. 6 C. moniliforme'. 7 C. cuairbita. S CThn^aitesii. .9 C. afteniULtiinv. 10 CconnctfUTrv. 11 CtetruophthalTnnmy.
XA.\ Till 1)1 IM
Tab. XVI
£.Senrrer. del.
X. amialufih.
XANTHIDIUM
Tal)MX
>> _/•
^my
LX.aiM.U€i.turyL. 2 J^.Btrbtssruiu. 3X.n-i.statu)n . 4 X.fasciadaht
E.Jei'tner. d&l .
XANTniDIT'M ARTllROi:)ES.\rrS ST.MTRASTIirM .
T.il) XX .
IX.fascLiZ/JaUurc. 2 X. cctocorn^-. 3 ji. conveniens. 4 A. In ens. 5 S.di'/eetunv.
E. Jenner. del .
STArRASTRUM
Tab. XXI.
^'^'e:3d
1 S. CH^^pidatufn, . 2 S. at y:stirhian . 3 S. Drc/ael . 4 S. muti^um.
5 S.orbTA^cUj.re.. 6 S. ticniidtxyit . 7 S. aUernans. S S. ddataJMirL .
9 S. margaritac^'(-t}rv'.
Ji.Jermer-, del
STAURASTRIM.
Tab. XXn.
2 S.pun ctuiaUim . 2 S. m u neat urn . S S. h irsuiiOH . 'J: S. ttLiferu?7u 5 S.BvstTLx . 6 S.asperum . 7 S.quadraftqulare.. S' S.spinosion^. ■9 S.polj-niorfjhian . JO S.cvrtonnan . Jl S. Itvcorne . 12 S. c/racilf .
J\.-Tcnticr ttct .
STAFRASTlll M
Tab.XXni.
■5^-. ^.W
/: J^e^niP?-. dgt .
I h vestitiirTL. 2 S. (wuleatum. 3 S. controrersuTn . 4 S.s/)on(fwsinn^.
5 S.sexcostatimi. 6 S.Jrarhne. 7 S. trtj'ace?-u?rc. S S .p aradoxuTn .
S> S.hrachiatum. lO.Slcvve. U S.Aricula. J2 S.aspen/m,.
T]:TME MORI'S
Tab.jarrx'.
/ T. Biebissoni/ . 2 T.(^7amt(a fi/s. JT. la^ns.
-E nfeftTLer, de,l .
ri: XH'M
TahJv.W.
mrnmnt^^
2 J< /fitayaj-itaceum. 2 F. Cylin d/Tj^ . 3 FDigitu^ 4F.interrupfiim 3 F. tr-ii?u:a.t7j?t7 62''. Breb/ssonii .
£.,/', tu.i: del .
DOCIDITM
T.il> X.Wl.
II). nodulo.s-unt. 2 D . b-un.caiu.)-n . SD.clayatiim . 4- D.jLhrercberqii. SI). rrvLfzutiarh. 61) asptrun i. .
-t,.Jenner: del
CJ.OSTE IIIT'M.
Talj.XXVn
^.■Tertner, del .
1 CLunvcloy. 2 C. cicerosum. 3 C. turgid mn.
CLOSTEHU M
Tab, XXVI II
£. JenrLer , del .
1 C. Icuvceo Latum,. 2 C.JIhreroher^ii. 3 C rfto/tili,/erujr>. . 4 C. Zeoblecn-VL . 3 C.Dian/:e . & C. ^enM^ri . 7 C. dcdyrrvotoaorL .
CLOSTERIITM
Tab.XXTX.
7 C. costatiun. 2 C. striolaturrt. 3 Cmtermediunt. 4 Canausfa/y/m ■5 C.attenucctum. 6 Cjuj^ijyuiumy. 7 Cjujzcidiun^.
J^.yJ^eruter'. fiel.
(."LOSlKlllUM
Tab.XW.
/ C. hnea. /am . 2 C. fialfsii. -3 C. rvstrahutt . 4 C. setaceurrt. ■5C.arzituni. 6 C. a)rmi .
li.Jenner, d^.
PEDIASTRL M SCENEDESMUS.
Tab. XXn.
# ^ Miffs' m. m
VBw sfflSk ,j,mM
i^^m^^K. ^^g^^^ mm^mmm^ ^
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n
V5i"^
m
E.J'ertner, d^l .
1 T.Tett^as. 2 I'Septactis. 3 F.hiradicLtum.. 4- r.bcradLCbtum/3. 5 J'.Selerupct. 6T.pertiisum. 7 F.^ATapoieortCs . 8 F-grxcnulatuni. 9F.£oryaruan. JOF.elliptiaon. llF.ari.ffuloswn, 12 S.qicadrLcaudn. 13 S.dcmorp/vus . J4 S.ctcictus. 15.S obliquiis. lO.S.ohtusv^s .
.Vl'lOGOA'TM. SPILKROZOS^MA. lilASrilUM. COS.MAKJIM. T;,!. XX\ll,S-i
PP
^ Jk ^ ^fX)''^
ill II t
I II t
Ji,\/erc7tA^, cleC
J A.lJfsmiflunn . 2 S.rerte(>ratu?rL. JJ:'.ru//eatu//i. /A'.si//j/o/>fftiu/i. S CF^LUserAus . 6 C.(/?xt?LatU77i. 7 Ciinrhi/n. . S C.ttirr/ifhini . ,9 C. curtum .
TETMEMORUS. PENIirM. DOCIDllTM (OSMAKIUM.
STAITRASTRFM. Dll)y.M()C'L.\JX)N. Tab.jmni Siipp*
] T. qrvniiLatus . 2r. .Jenneri. 3Tmargari(:acei/.ni./3. 4'I).Eh)-enheryii,j3.
J D. bandumy. 6 C. nLmyaritife.nini. 7 C. BroomeC S C.tctra/^iphthalm urn .
S C. orb ica. lo,re . JO S. ruspida turn . U S. rnr'r??? e . J2R fUrciqeriL?.
E' ^/trnru^r del
SPmOTj;.\lA. AXKl.srUDDKSAirS. I'ENJUM. CLOSTl^JUrM.
STA-URAS'mUM. PKBIASTRFM. SCENEDESMUS. Tab.XXXlV.Supp!
] S. /•enfU^isata.. 2 S.obscura . ,3 ^.falcatus. 4- 1' r]osten<>ides. ■5 C. aciituTn . 6 S.pol)mo}~phum. 7 S. hrevispina . & S.ti'icoryte. .9 S. tnrirUiculosum. JO S.piifigen^ 21 S. (/iiadra7ic/iila}r J2 S. hmafum . /.l S 11(11 fi'rnm . J'/- S.iefifentm . IST.snuplt^j-. /6 S.ari(t//s. J7 Schi^lex.
J:^. /f:ftrur.r, <&/.
APTOr.O.M'M. SIMI.KIIOZOS.MA. MICIIASTKUIAS. DOfmU'M. CI.OSTKIMOI. l-rASTin-.M. AllTimODi-SMrS. UYALOJIIKCA.
STAI-KASIUUM. SCENl-:j>ESMrS. Tab \X\V Supij!
lJ^aile)L 2 SpK-puMvutrv. 3 If./'oliace.cL. 4'MBaileyi\ SMTorreji. '^B. coronation. 7D.cortstrictiim. SDjxodosum,. SD.verticillatimi. 10 Ctenemnitm. Jl Ccuspidaticm . £2 CTeiULS. J3£.coi~mitu>rL. 14 H.cTienatum.. ijA.mmutus. JGH.duhia. 17 S.crenatum. IS'. S. minor. l&S.ru^ulcsion. 20S.scabrum. 21 S.bacCllxire. 23 S.pileolcLtum . 23 S.Qlohiifanou. 2 4 S .erhinatum . 23 S.capitiLiii77t. 26 S-pyr^mceunh. 27Sce.an/f/mifti/s.
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