[409] GRAPHIC KEYS FOR THE IDENTIFICATION OF SPHAGNA

Transcription

1 [409] GRAPHIC KEYS FOR THE IDENTIFICATION OF SPHAGNA BY M. FEARNSIDES The Botany School, Cambridge (With 5 figures in the text) CONTENTS PAGE Introduction Note on the main subdivisions of the genus A general key based on hand-lens characters Explanation of conventions used in graphic keys. 418 List of authorities and synonyms The use of the graphic keys A technique for the preparation of reference material 422 INTRODUCTION ft^here are probably a large number of ecologists and field botanists I who find the need for some acquaintance with the Sphagnum genus from time to time. The literature on the subject is rather unwieldly, much of it is written in foreign languages and it is often difficult to obtain and inconvenient to handle. In general, too, only after considerable experience with the whole genus can species be recognized rapidly in the field or laboratory. The following graphic keys are based on a generalized system of Sphagnum classification, and they purpose no criticism of individual systems. They are intended, not as an infallible guide to the diagnosis of "difficult" species (for which classical monographs must always be consulted), but for placing the main body of a field collection in a systematic scheme. The experienced taxonomist rarely runs through a verbal key before determining a famihar species; he sums up his optical impressions at once, and compares them mentally with the appearance of some well-known "type". The field ecologist, on the other hand.

2 410 M. FEARNSIDES has little time or opportunity for assembling a full type collection. Since he works probably with onh' a limited number of members of the genus, the meaning of comparative terms even in English descriptive texts remains largely a matter of guesswork. Ambiguities and difficulties in translation lead constantly to a consultation of the illustrations, and these are often of a very diagrammatic nature. By introducing a compact arrangement of realistic drawngs, the author hopes to a\'oid some of these disadvantages, and to gi\-e at a glance the general characters for which the ecologist has, formerly, had to rely on experience alone. Once the conventions used in the graphic kej's ha^ e become familiar, the drawings should call up the sort of picture that is seen with the microscope during any examination. They will then perhaps serve as a rough and ready pocket type collection, and save time in the naming of typical samples. The material from which the plates were made consisted of some 450 preparations, chiefly from herbarium material belonging to the \'axtbiologiska Institution of Uppsala, Sweden. The specimens were selected for their authoritatn'e naming and reliable habitat records (much of the material having been obtained by e.xchange from the collections of Jensen, Lindberg, \\'arustorf, etc.). The herbarium samples ha\e since been generously supplemented by specimens from the personal collections of Prof. Du Rietz and Prof. Osvald, and come from Scandinavia, the British Isles and New Zealand. Other specimens were collected in North-west Europe by the author. The nomenclature and specific status given to the Sphagna illustrated here, represented the unpublished \'iews of Prof. Du Rietz in Apart from the group stat\is of.s'. siil)siruiutiini, S. pvlaiiii and 5. dii!^stro)ini, the present arrangement corresponds fairly well to Le Roy Andrews's recently re\"ised system.^ Some uine " species" not recognized iu Le Roy Andrews's paper are depicted for convenience of reference to earlier literature, while a further three still maintained in the British Census Catalogue are omitted as of little significance to the ecologist. The general separation of the genus into groups has not been treated graphically because of tlie difficulty of illustrating nonspecific characters. For convenience of reference, and as an aid in field work, diagnostic group characters recognizable with a haud-leus are arranged in a text key immediately preceeiing the plates. It ' Ditierences are noted in the list of s\iioiiynis on p. 11.

3 Graphic Keys for Sphagna 411 has seemed to the author unsatisfactory to attempt to exclude microscopic characters from the key entirely, and it may be necessary in difficult cases to rely on such characters altogether. Before closing this introductory section the author would like to express her sincere gratitude to Prof, Du Rietz of Uppsala University in whose laboratory she was privileged to work for several months. It was at his suggestion and with his participation that the technique was elaborated and the groups revised. It was only through his wide taxonomic experience and linguistic capacity that the scope of the present contribution could be made representative of general Furopean Sphagnum systematics. NOTE OX THE MAIN SUBDIVISIONS OF THE GENUS In most instances separation of the Sphagna into the subgenera Inophloea and Lithophloea is quickly accomplished in the field. Similarly the divisions of the Lithophloea (the Warnstorf "groups" are generally recognized after a little practice without microscopic examination. For the general ecologist, a key is appended which summarizes a number of useful field characters in a compact form. Unfortunately, the macromorphology of Sphagna can very rarely be regarded as of accurate diagnostic value, even though this is responsible for the characteristic "look" of species in their natural habitat. The general appearance of the living Sphagnum, indeed, not only attracts the eye of the collector but is the very basis upon which the ecologist builds up an impression of distribution, indicator significance, etc., in the field. An attempt is therefore being made to summarize certain aspects of the general macromorphology of the group which does not lend itself to the closer definition required by a key. Very broadly, the Palustria (Cymbifolia) group may be described as coarse and vigorous, with a characteristic "hooded" leaf; the Acutifolia are delicate, pinkish, regular, cushion-forming; the Cuspidala with tufted heads, sharply rolled and somewhat drepanoclade leaf, often aquatic or damp-loving; the Squarrosa with pointed branchlets and often recurved leaf, growing only m eutrophic situations; Rigida with soft, untidy habit, in loose cushions; Subsecunda most variable of all, with loose, often coarse growth, sometimes lax, gelatinous, and aquatic, sometimes irregularly compact, with branchlets crowded, stem often clothed with large leaves.

4 412 M. FEARNSIDES In colour, the genus in the living state displays every shade from purple-pink, crimson and russet, through yellow, yellow-green and olive-green, to a greenish or purplish brown, or even black. The first three tints appear only in the Acutifolia, and in Sphagnum magellaniciim of the Palustria; the last only in submerged Subsecunda. An orange-yellow coloration is typical of certain Subsecunda, but appears also in the Squarrosa {Sphagnum teres) and in Rigida {Sphagnum compactum). The remaining Sphagna tend to be green or yellow-green, although they may assume a delicate straw colour or deep olive-green in certain conditions. Green specimens of almost every typically coloured Sphagnum are known. The arrangement of the groups in the plates is determined rather by space than considerations of natural affinity, since the taxonomic problem of group status lies outside the seope of this paper. Reference should be made to recent publications by Le Roy Andrews (1936) and Aberg (1937) for details of taxonomy. For example, the Warnstorf group Subsecunda is reduced by both these authors to specific rank. For correlation with earlier nomenclature, those Warnstorf Subsecunda species are illustrated as varieties of Sphagmim subsecundum if recognized by Aberg (1937). The Sphagna crassicladum and camusii and Sphagmim turgiduhti^i of the British Census Catalogue are omitted as extreme modifications of Sphagnum subsecundum var. bavaricum and var. rufescens respectively. [Sphagnum subsecundum var. rufescens (sensu Warnstorf) which has recently (Sherrin, 1937) been struck oflf the British Census Catalogue is still recognized by Aberg as a south-east Swedish species. The author has not examined any satisfactory material of this Sphagnum, so that the illustration has been based on the identity of Aberg's description of the branch-leaf pore structure with that for Sphagnum subsecundum var. bavaricum which was drawn from preparations.] S. houii and S. obesum of the British Census Catalogue are regarded by the author as coming very close to 5. subsecundum var. inundatitm. S. pylaeai is not regarded by Le Roy Andrews as a variety of the old Subsecunda, but as an independent species within the Cuspidata '' series''. As to the Cuspidata group of the British Census Catalogue the present keys make two omissions; Sphagnum falla.x, which seems to differ little in both taxonomic and ecological range from S. recurviiin = S. apiculaium of the key; S. torreyanum, a species evidently nearly related to S. cuspidatum. In the Acutifolia, Sphagnum subtile and S. tenerum of the British Census Catalogue, are not illustrated, as differing liftle from S. acutifolium. On the other hand a S. angermannicum is depicted which is probably identical with S. molle var. Hmbatum of the British Census Catalogue. From very limited material this Sphagnum has seemed to the author to merit recognition as a separate species. The monotypic group Truncata is now fused by Le Roy Andrews with the Squarrosa, which is illustrated here on another plafe. The revised Lithophloea series requires closer inspection than the Warnstorf group, with very little corresponding improvement in the ease of recognition.

5 Graphic Keys for Sphagna 413 A GENERAL KEY Based on branch teaf characters visible with the hand-lens A. Branch leaves (B.L.) cucullate (hooded) cortical cells with spiral fibrils Subgenus Inophloea = Palustria (Cymbijolia) B. B.L. non-cucullate: no spiral fibrils toothed or truncate at apex Subgenus Lithophloea I. B.L. broadly truncate, large, very revolute margins (a) B.L. with resorption-furrow Rigida (ft) B.L. without resorption furrow (i) Stem leaves smaller than B.L. (ii) Stem leaves larger than B.L. II. B.L. not broadly truncate, acute or toothed at apex Truncata (S. angstromii) Acutifolia (S. angermannicum) (a) B.L. broadly ovate. Chlorophyllose cells not triangular. (Colour never red) (i) B.L. obtuse, very revolute margin subsecunda (ii) B.L. truncated cuspidate less revolute Squarrosa (b) B.L. narrowly ovate. Chlorophyllose cells triangular with convex (ventral) exposure. (Colour never red) Cuspidata, series Ovalia (S. tenelliim) (c) B.L. ovato lanceolate-lanceolate, acute. triangular-trapezoid Chlorophyllose cells (i) B.L. somewhat undulate or crispate; with greater convex (dorsal) exposure. Stem leaves very small Cuspidata, series lanceolata (ii) B.L. neither undulate nor crispate; chlorophyllose cells with greater concave (ventral) exposure. Stem leaves relatively larger than in (c) (i) (a) Very numerous branchlets in each fascicle Polyclada (S. wulfiannm) ((3) Generally fewer than 7 branchlets per fascicle Acutifolia

6 SPHAGNA A CUTIFOLIA Stem leaf Porosity Septation Branch XIO ofslein Plant Branch leaf and fibrosity leaf Diagnosis cortex colour Phyllotaxis pore type ot stem leaves ^ I 4 i ; i S.fimbrialum S. girgensohnii S. russowii own f S. fuscum S. warnslorfi S. quinquefarium S. rubellum S. plumulosum S. ncutifolium S. molle As in all other members of erou * J, 0 amrriconum) [S. nngprmanirum) Fig. I. For explanation of conventions employed see p. 418.

7 SPHAGNA CUSPIDATA Stem Branch leaf leaf Diagnosis S. lindbergi Branch leaf pore structure Convex Concave superficial superficial view view ' S. riparium S. tenellum S. cuspidatum * S. dusenii S. jensenii S. obtusum Fig. 2. For explanation of conventions employed see p. 418.

8 SPHAGNA PALUSTRIA (CYMBIFOLIA) CucuUate leaf tv-pe -ta JCk S. imbricatum S. papillosum S. magelhnicum S. centrale S. imbricatum is^pa, var. affine j * " SPHAGNA TRUN CAT A (single example) SPHAGNA RIGIDA S. papillosum var. laeve Convex Median internal focu8 Concave Leaf section Branch leaves 1 vertical axis T... Stem leaves X10 horizontal axis S. angstromii S. compactum S. strictum Fig. 3. For explanation of conventions employed see p. 418.

9 SPHAGNA SVBSECUNDA Stem section. Stem leaf X10 Stem leafx200. Branch leaf X200. S. pylaiei S. contortum var. typicum var. platyphyllum 5. subsecundum var. typicum var. inundatum var. havaricum. rufescens var. auriculatum SPHAGNA SQUARROSA Branch leaf XI0, S. squarrosum S. teres Fig. 4. For explanation of conventions employed see p PHYT. XXXVII. 5

10 418 M. FEARNSIDES Explanation of conventions used in graphic keys Stem leaves are in black and white outline. Fimbriation is depicted realistically. Fibrillation is indicated by hand stippling. The extent of purely chlorophyllose tissue (without hyaline interruptions) is suggested by half-tone shading. The schematic "mid-rib" indicates the usual amplitude in size for well grown-leaves, and follows Warnstorf's figures at a scale of X 10. Branch leaves are in half-tone shading. They represent the form most usually found proximally on upturned branchlets (see preparation technique). Scale is not given, since size is rarely diagnostic. Phyllotaxis is shown by the view through a low power binocular microscope with exaggerated illumination and relief. Details of pore arrangement and structure are drawn at various scales to suit the minuteness of detail required. When the leaf is observed by superficial focus from the convex side, the sketch is always truncate obliquely below the rectangle if from concave side, the sketch is obliquely truncated above (the two views fitting together, when both are shown, along a dotted hne to indicate deepening of focus on the same material). When a median internal focus is required this is depicted always as a quadrilateral between the upper and the lower focus views (5. palustria). Leaf sections are depicted realistically from typical material. Deep shading is used only for deep-staining chlorophyllose cell structure. Half-tone is used as indicated above, and for all parts of the microscopic structure which retains a light stain. Pores are indicated as white openings in the half-tone ground; outlined if they are distinct, ringed if they are bordered, or left as perforations if faint (as in S. ohtusimi). Pseudopores (of equal diagnostic value in certain groups) are indicated as imperforate outlines on the half-tone ground.

11 Graphic Keys for Sphagna 419 List of authorities and synonyms SPHAGNUM (Dill.) Ehrh. *acuhfolium Ehrh. = \capillaceum (Weiss) Schrank var. subtile (Russ.) Warnst. var. tenerum (Aust.) Warnst. *ameyicanum Warnst. *angermannicum Melin *]dngstrdmii C. Hn. *apiculatum (H. Lindb.), see recurvum *\bauicum, Russ. *centrale C. Jens. *\compactum DC. *contortum Schultz *var. platyphyllum (SuU.) Aberg *^cuspidatum Ehrh. var. torreyanum (SuU.) *\dusenii C. Jens. "'{fimbriatum, Wils. *\fuscum (Schimp.) Klinggr. *]girgensohnii Russ. *\imbricatum (Hornsch.) Russ. *var. affine (Ren. et Card.) Warnst. ]*jensenii H. Lindb. *^lindbergii Schimp. * ^magellanicum Brid. 'fwow«svi\\. = tabulare SuU. *^obtusuni Warnst. *palustre L. = ^cymbifolium Warnst. *^papillosum Lindb. *var. laeve Warnst. *\plumulosum Roll. *^pulchrum (Lindb.) Warnst. *]pylaiei Brid. *]quinquefariuni (Lindb.) Warnst. \recurvnni Palis. = apiculatum (H. Lindb.) *var. angustifolium C. Jens. *var. amblyphyllum Russ. var. fallax (Klinggr.) *'[ripanum, Angstr. *rubellum Wils. *russowii 'Vla.mst. = ^robustum (Russ.) Roll. *\squayrosum Pers. *]styictum SuU. *\subsecunduyn Nees *var. auyiculatum (Schimp.) Lindb. = var. obesum (Wils.) Warnst. ex payte *var. bavayicum (Warnst.) Aberg = var. crassicladum Warnst. ex payte = var. camusii (Card.) Warnst. *var. inundatum (Russ.) Aberg = var. obesum (Wils.) Warnst. ex parts = var. holtii Warnst. *var. yufescens (Br. germ.) Aberg = var. tuygidulum (Warnst.) *'\ienellum Peis. = molluscum Warnst. *'\teres (Schimp.) Angstr. *^waynstoyfii Russ. \wulfianuyn Girg. * Figured in the graphic keys. f Recognized in Le Roy Andrews's revised system (1936). 27-2

12 420 M. FEARNSIDES THE USE OF THE GRAPHIC KEYS Apart from that for the Sphagna subsecunda, the keys are all constructed on the same plan, and are intended to give at a glance all those characters (other than growth form) which are relevant for the quick determination of any Sphagnum species. The keys are arranged so that each feature illustrated is part of a series leading finally to a specific name. These series are arranged to be followed from left to right in all groups, except Palustria (Cymbifolia), Truncata, and Rigida (Fig. i) where they are placed down the page on account of space. The following explanation applies particularly to Figs. I and 2; an additional note on Fig. 4 appears later. In different groups, of course, different characters are of diagnostic importance, so that the same features do not necessarily appear on every plate. Within each group, however, all characters of diagnostic value for recognizing any specimen are illustrated in the vertical columns in their full range. A survey of these columns provides the variation amplitude of a number of diagnostically useful features within each group. The horizontal lines connect the specific manifestations of each of these characters in tum. The vertical order of the species list is decided as far as possible by the ease of diagnosis, so that the investigator may dispense with readily determined species early in the key. If a specimen can be recognized at low magnification on a single character, it will generally appear towards the top of the list, and the character will be illustrated towards the left-hand side of the page. If the species is only identifiable after the confirmation of a number of characters, it will be found towards the bottom of the page. The final separation of this species from adjacent members of the list will then depend on a character illustrated towards the right-hand side of the page. A diagonally sloping half-tone band is drawn to cross the successive columns just where each character becomes of specific diagnostic importance; so that, except for confirmatory information it is seldom necessary to consult characters to the right of this band. If, moreover, a specimen suspected of belonging to a familiar species fails to exhibit the character emphasized by the half-tone band, it is advisable to start following the key at once (from the top left-hand corner, and working across the lower triangle from left to right). The vertical system of arrows is used to avoid a repetition of drawings. They act as "ditto" marks below the lower drawing in each column and above the uppermost. The horizontal arrows merely

13 Graphic Keys for Sphagna 421 direct the eye across the columns to the appropriate specific name. Where more than one horizontal row of arrows passes across a single drawing (see Fig. 4), that drawing is applicable to both or all the species indicated; where the row crosses a perpendicular arrow (see Fig. i), the appropriate illustration will be found in the direction of that arrow. By following these systems of arrows one may build up a more complete picture of the species than is necessarily required for its identification. The vertical columns also serve, by presenting the range of variation within the group, to explain the meaning of such relative terms as "pores numerous", "pores large", "pores bordered", etc., which offer so much difficulty to the investigator possessing only a limited acquaintance with the group. On the other hand, it must be emphasized that the drawings can only depict what have seemed to the author to be fairly representative types. They are not intended to exclude minor divergences, but rather to indicate graphically the nature of the differences upon which the keys have been based. Suppose, for example, a member of the Sphagna acutifolia awaits identification. If its stem leaves are of the fimbriatum or girgensohni t3^e, the species, as the half-tone band indicates, requires no further confirmation of its identity; but suppose it to possess a spatulate stem leaf, and the possibility of its being a variant of several species arises: the porosity of the stem cortex will then decide whether or not it is S. russowi. A marked chestnut-brown coloration is completely diagnostic for S. fiiscum; five-rowed phyllotaxis is generally a good character for recognizing S. warnstorfl and quinquefarium and these are then separated immediately on stem or branch leaf form, with the additional check of leaf-pore structure in more doubtful cases. As one works through the key, the species characters become less easy to define and more data are required for making a determination. However, if the individual characters be noted in the order suggested by the headings at the top of the figures, one may be confident that no character is being examined unnecessarily even as regards the rapid determination of the species. For speed and convenience in making identifications, macrocharacters have, wherever possible, been dealt with first; so that a number of possibilities may be adopted or discarded after hand-lens examination, as in the early parts of the Acutifolia and Cuspidata keys. If lens diagnosis fails, the keys next take one on to microscopic characters of increasing subtlety (although macro-characters

14 422 M. FEARNSIDES may again be called upon to supply confirmatory evidence). Unfortunately, in the Sphagna palustria, there are no useful lens characters of diagnostic importance. S. imbricatum, however, may be detected with the lowest powers of the microscope; S. papillosum requires rather more minute determination; 5. magellanicum, if not of the typical reddish colour, and S. centrale must be examined by the "differential focus" technique. (The author regards sectioncutting as unnecessary for the first four species of this group, and only useful for extra confirmation in S. imbricatum var. affine.) The difference between S. pahistre and the variety laeve of S. papillosum can of course only be detected in the plane at right angles to the leaf surface (sections therefore are necessary only in separating the last two species). With regard to the 5. subsecunda, Fig. 4, the method of presentation is necessarily rather different on account of the complex character of the key. Since the group has been revised by Aberg as recently as March 1937, it has seemed appropriate to follow his classification scheme. The sketches, though made independently, and from different material, have therefore been arranged as illustrations to his key. No single system of characters can be recommended for diagnosis within this group; the species differences are generally based on character aggregates or are of a statistical nature. The half-tone band convention is therefore not employed here. This key is read from left to right, beginning with the stratification of the stem cortex, and differentiating next on stem leaf size, and later on relative pore frequency of the leaf faces. The 5. squarrosa are arranged in the same columns merely to maintain uniformity on the figure; if space had permitted, they would more fittingly have appeared beside the Tnmcata and Rigida groups. A TECHNIQUE FOR THE PREPARATION OF REFERENCE MATERIAL Write duplicate labels for slide and test-tube. Heat water-bath. Select a branched specimen of Sphagnum sample. Remove one branch, and mark the remaining as " type herbarium material". Place in warm KOH solution (all unused test-tubes and water and KOH bottles stand in a water-bath). Bring to boil and boil for a few seconds. Transfer liquid to another vessel. Add hot water and boil again. Rinse and boil again. Rinse in cold water. Rinse in alcohol. Transfer branch to large glass dish of dilute alcohol. Strip off branchlets from one (vertical) half of the stem if they grow densely.

15 Graphic Keys for Sphagna 423 Select six vigorous upturned branchlets and, if necessary, three pendent branchlets. Strip off and discard remaining fascicles. Transfer stripped stem and the selected branchlets to staining medium gentian violet in alcohol. Leave in stain 3-6 min. Remove the seven (or ten) objects from the stain. Wash in dilute alcohol. Wash in large vessel of distilled water. Wash in large vessel of dilute glycerine. Leave to stand in watch-glass of pure glycerine. -^ Pipette reservoir _ t Hooked Fig. 5 Select a portion of stem and dissect off six stem leaves, together with a small piece of stem cortex. Arrange objects centrally in a drop of pure glycerine* on slide (with the help of a binocular) so that the three leaves on the left-hand side lie concave side uppermost and vice versa. Lower cover slip immediately. Select an originally upturned branchlet and dissect off six leaves. (A number of leaves are stripped off with a fine scalpel and the larger, i.e. the proximal ones, selected.) Arrange in a second drop of glycerine immediately below the label on the slide so that the three on the left-hand side lie concave side uppermost, and * For semipermanent preparations the glycerine may be replaced by a hardening medium such as gum chloral, which makes the slides more convenient to handle although the stain is more apt to diffuse out.

16 424 M. FEARNSIDES vice versa. (An-ange a further six leaves from pendent branchlets below the former if required.) Lower cover-slip immediately. Select two or three uninjured, originally upturned, branchlets and the uninjured portion of stem; cut the stem into two parts. Lay the objects in needle grooves in a pith cylinder draw out the branchlets slightly so that the leaves come to lie fiat against the stem. Cut sections. Place sections in water and remove the floating pith (the sections sink to the bottom). Pierce a small pithslice with a hooked wire and push the wire up through the nozzle of a 5 c.c. pipette (see Fig. 5). Draw up water gently until the pithslice filter lies against the mouth of the pipette. Then filter the sections from water in the watch-glass by suction. The lightest, therefore thinnest, sections adhere to the pithslice. Pour off the excess water from the broader, open end of the pipette. Suck the pithslice as free as possible from capillary water. Float off sections into a drop of glycerine on the slide. Remove larger pith fragments or thick sections (with the help of a binocular). Lower cover-glass. Sealing: Heat a mounted needle until almost red-hot. Dip into mounting wax and transfer the fluid wax to the slide. The fluid wax should not at first come into contact with the cover slips, but form a raised border of even thickness about i mm. from them. Next, take the hot needle and press the remelted wax towards the margin of the cover slip, so that it makes contact along the whole border. Now follow the margin of the cover-glass with a very hot needle so that the wax runs some 0-5 mm. over the border and sealing is complete. The outer border of the wax frame may be straightened by running the needle round the outer edge. Finally, the surface of the wa.x is smoothed (to prevent damage to or by microscope objectives during investigation) by holding the slide in a spirit flame for a moment. (Great care must be taken not to boil the glycerine or allow the cover glasses to slip out of place.) REFERENCES ABERG, GERHARD (1937). Untersuchungen uber die Sphagnum-Arten der Gruppe Subsecunda in Europa. Ark. Bot. 29 A, No. i. LE ROY ANDREWS, A. (1935). Notes on the Warnstorf Herbarium. Ann. Bryol., Hague. SHERRIN, W. R. (1937). Census Catalogue of British Sphagna, compued for the British Bryological Society. (1927). Handbook of British Sphagna. WARNSTORF, C. (191 I). Sphagnologica Universalis.

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