SDS. Nai 2 2 Ba Be Hs eee Oe oO OT oF SK ANRKK x PLLSLS LS LIA NAN POETS SAAN INIT TInAnTIna nAnANANnnniAnnnnnnnanannnnannnnnnn At Ie xno D A et D ed tt hae mB Ae DAPI PATA A Ae Is bh oS te AAS» Ae Bs ALBERT R. MANN LIBRARY AT CORNELL UNIVERSITY MARY “HT ON ik - i u = ] ‘ fff i re’ Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu3 1924084753122 f is pee Rete fee ee ND ES, ’ s Bed nas ate bon Aimet me od sah Seg regen # ‘ fiprT statis ON THE FERTILISATION OF ORCHIDS hy INSECTS, do. ae. CHARLES DARWIN’S WORKS. Origin of Species by Means of Natural Selection; or, The Preservation oi Favored Paces in the Struggle for Life. From sixth and last London edition. 2vols, xzzmo. Cloth, $4.00. Descent of Man, and Selection in Relation to Sex. With many Tlustra- tions. A new edition, z2zmo. Cloth, $3.00, A Naturalist’s Voyage around the World. Journal of Researches into the Natural History and Geology of Countries visited during the Voyage of H. M S. “Beagle.” ‘Illustrated with Maps and zoo Views of the places visited and re chiefly from sketches taken on the spot, by R. T. Prircuerr. 8vo. Cloth, $5.00. Also popular edition. 1zmo., Cloth, $2.00. The Structure and Distribution of Coral Reefs. Based on Observations made during the Voyage of the ‘‘ Keagle.” With Charts and Illustrations. zemo. Cloth, $2.00. 7 Geological Observations on the Volcanic Islands and Parts of South America visited during the Voyage of the “Beagle.” With Maps and Illustrations. zamo. Cloth, $2.50. Emotional Expressions of Man and the Lower Animals. 12zmo. Cloth, 3-50. The Variations of Animals and Plants under Domestication. Witha Preface by Professor Asa Gray. 2 vols. LIllustrated. Cloth, $5.00. Insectivorous Plants. x12mo. Cloth, $2.00. Movements and Habits of Climbing Plants. With Illustrations. x12mo. Cloth, $1.25. The Various Contrivances by which Orchids are Fertilized by Insects. Revised edition, with Illustrations. 12mo, Cloth, $1.75. The Effects of Cross and Self Fertilization in the Vegetable Kingdom. rzmo. Cloth, $2.00, Different Forms of Flowers on Plants of the same Species. With Illus- trations. rzmo, Cloth, $1.50, The Power of Movement in Plante. By Cuartes Darwin, LL.D., F.R.S., assisted by Francis Darwin. With Illustrations. 12mo. Cloth, $2.00. The Formation of Vegetable Mould through the Action of Worms, with Observations on their Habits. With Illustrations. 312mo. Cloth, $1.50. New York: D. APPLETON & CO., PUBLISHERS. THE VARIOUS CONTRIVANCES BY WHICH ORCHIDS ARE FERTILISED BY INSECTS. Bx CHARLES DARWIN, M.A., F.BS., &. SECOND EDITION, REVISED. WITH ILLUSTRATIONS. NEW YORK: D. APPLETON AND COMPANY, 72 FIFTH AVENUE, 1895. PREFACE TO THE SECOND EDITION. 12 Tue first edition of this work was published early in the year 1862, and hus been for some time out of print. During the two or three years after its appearance I received, through the kindness of various corre- spondents: in different parts of the world, a large number of letters, especially from Fritz Miller in South Brazil, communicating to me many new and curious facts, and calling my attention to some errors. Various memoirs on the fertilisation of orchids have also since been published, and I have myself examined several new and striking forms. A large amount of matter has thus been accumulated; but the present volume would be rendered much too long if the whole were introduced. I have, therefore, selected only the more interesting facts, and have given a brief abstract of the several published papers. The work has thus been remodelled; and the additions and corrections are so numerous that I have found it impossible to follow my usual plan of giving a list of them. I have, however, vi PREFACE TO THE SECOND EDITION. appended, in chronological order, the titles of all the papers and books on the fertilisation of the Orchidee which have been published since the appearance of the first edition of the present book. Finally, I will remark that any reader who wishes merely to see how wonderfully complex and perfect are the adaptations for the fertilisation of these plants had better read Chapter VII. on the Catasetide. The account of their structure and of the action of the several parts will, I think, be intelligikle, if he will first glance at the explanation of the terms given at the close of the Introduction. List of Papers and Books bearing on the Fertilisation of the Orchidex, which have been published since the appearance of the First Edition of this Work in 1862, arranged in Chronological Order. —to Bronx, H. G.—‘ Charles Darwin, tiber die Einrichtungen zur Be- fruchtung britischer und ausléndischer Orchideen.’? With an Appendix by the Translator on Stanhopea devoniensis. Stuttgart, 1862. Gray, Asa.—On Platanthera (Habenaria) and Gymnadenia in ‘ Enunieration of Plants of the Rocky Mountains.’—American Journal of Science and Arts, Second Series, vol. xxxiv., No. 101, Sept. 1862, p. 33. Gray, Asa.—On Platanthera hookeri, in a review of the first edi- tion of the present work.—American Journal of Science and Arts, vol. xxxiv. July 1862, p. 143. Axperson, J.— Fertilisation of Orchids’—Journal of Horticulture and Cottage Gardener, April 21, 1863, p. 287. Gossr, P. H.—‘ Microscopic Observation on some Secds of Orchids, —Journal of Horticulture and Cottage Gardener, April 21, 1863, p. 287. Gray, Asa.—On Plutanthera (Habernaria) flava and Gymnadenia tridentate.—A merican Journal of Science and Arts, vol. xxxvi. Sept. 1863, p. 292. JOURNAL OF HorTICULTURE anp CoTTaGE GARDENER.—March 17, 1863, p. 206. ‘On Orchid Cultivation, Cross-breeding, and Hybridising.’ Scupprer, J. H.—On Pogonia ophioglossoides. Proceedings of the Boston Society of Natural History, vol. ix. April, 1863. Treviranus.— Ueber Dichogamie nach ©. C. Sprengel und Ch Darwin. § 8. Orchideen.’—Botanische Zcitung, No. 2, 18638, p- 9. Vili LIST OF PAPERS AND BOOKS. TREVIRANUS.—‘ Nachtrigliche Bemerkungen tiber die Befruchtung einiger Orchideen.’—Botanische Zeitung, No. 82, 1863, p. 241, Tren, R.—‘On the Fertilisation of Disa grandiflora, Linn.”— Journal of Linnean Society, Botany, vol. vii. 1863, p. 144, West or Scorranp HorticunturRaL Macazine.— Fertilisation of Orchids,’ Sept. 1863, p. 65, Criicer.—‘ A few Notes on the Fecundation of Orchids, and their Morphology.—Journal of Linnean Society, Botany, vol. viii. No. 31, 1864, p. 127. Scort, J.—‘ On the Individual Sterility and Cross-impregnation of certain Species of Oncidium.’—Journal of Linnean Society, vol. viii. No. 31, 1864, p. 162. Moaeripcz, J. TRAHERNE.— Observations on some Orchids of the South of France.’—Journal of Linnean Society, Botany, vol. viii. No, 82, 1865, p. 256. Trimex, R.—‘ On the Structure of Bonatea speciosa, Linn., with - reference to its Fertilisation.—Journal of Linnean Society, vol. ix. 1865, p. 156. Ronrsacu, P.— Ueber Epipogium gmelini’—Gekrénte Preisschrift, Gottingen, 1866. Detrrxo.—‘ Sugli Apparecchi della Fecondazione nelle Piante antocarpee.” Florence, 1867. [itprbranp, F.—‘ Die Geschlechter-Vertheilung bei den Pflanzen,’ &c. Leipzig, 1867, p. 51, e¢ seq. Himprsranp, F.— Frederigo Delpino’s Beobachtungen tiber die Bestéubungsvorrichtungen bei den Phanerogamen.’—Bota- nische Zeitung, No. 34, 1867, p. 265. MogerincE, J. TRAHERNE, on Ophrys.—‘ Flora of Mentone,’ 1867 (2). Plates 43, 44, 45. Weatez, J. P. Mansen.— Notes on the Structure and Fertilisation of the Genus Bonatea, with a special description of a Species found at Bedford, South Africa,’—Journal of Linnean Society, Botany, vol, x. 1867, p. 470. Hinpesrann.—‘ Notizen iiber die Geschlechtsverhdltnisse brasili- anischer Pflanzen. Aus einem Briefe von Fritz Miiller’— Botanische Zeitung, No. 8, 1868, p. 113. LIST OF PAPERS AND BOOKS. 1x MU.ier, Frivz. Ueber Befruchtungserscheinungen bei Orchi- deen.’—Botanische Zeitung, No. 39, 1868, p. 629, Miuier, Hermann.— Beobachtungen an westfalishen Orchideen.’ —Verhandlungen des nat. Vereins fiir Pr. Rheinl. u. Westf. 1868 and 1869. Darwin, CHartes.— Notes on the Fertilisation of Orchids’— Annals aud Magazine of Natural History, Sept. 1869. De.rino.— Ulteriori Osservazioni sulla Dicogamia nel Regno vege- tale.’ Parte prima, Milan, 1868-69, pp. 175-78. Mocertivex, J. Tranerne.— Ueber Ophrys insectifera, L. (part). —Verhandlungen der Kaiserl. Leop. Carol. Akad. (Nova Acta), tom, xxxv. 1869. Miuirr, Frrrz.—‘ Ueber einige Befruchtungserscheinungen.’— Botanische Zeitung, No. 14, 1869, p. 224. Miter, Frrrz.—‘ Umwandlung von Staubgefissen in Stempel bei Begonia. Uebergang von Zwitterbliithigkeit in Getrenntblii- thigkeit bei Chamissoa, Triandrische Varietit eines monan- drischen Epidendrum.’—Botanische Zeitung, No. 10, 1870, p. 149. Weate, J. P. Manset.—‘ Note on a Species of Disperis found on the Kageberg, South Africa..—Journal of Linnean Society, Botany, vol. xiii. 1871, p. 42. Weate, J. P. Manset.—‘ Some Observations on the Fertilisation of Disa macrantha.—Journal of Linnean Society, vol. xiii. 1871, p. 45. Weatt, J, P. Mansen.—‘ Notes on some Species of Habenaria found in South Africa.’—Journal of Linnean Society, vol. xiii. 1871, p. 47. Currseman, T. F.—‘On the Fertilisation of the New Zealand Species of Pterostylis.’—Transactions of the New Zealand Insti- tute, vol. v. 1873, p. 352, Miuer, Heemann.— Die Befruchtung der Blumen durch Insekten,’ &c. Leipzig, 1873, pp. 74-86. CuErseman, T. F.—‘ On the Fertilisation of Aciantkus cyrtostilis,’ —Transactions of the New Zealand Institute, vol. vii. 1874 (issued 1875), p. 349. J x LIST OF PAPERS AND BOOKS. .Miutes, Hermann.—‘ Alpine Orchids adapted to Cross-fertilisation by Butterflies.’—Nature, Dec, 31, 1874. De.rixo.—‘ Ulteriori Osservazioni sulla Dicogamia nel Regno vegetale.’ Parte seconda, fase. ii. Milan, 1875, pp. 149, 150. Lusgocg, Sir J.— British Wild Flowers.’ London, 1875, pp. 162- 175. Firzazratp, R. D.—‘ Australian Orchids” Part I, 1875, Part IL. 1876. Sydney, New South Wales, CONTENTS. INTRODUCTION ..0 4.0 eee eevee eww Pages 1-5 CHAPTER I. OPHREZ. Structure of the flower of Orchis mascula — Power of movement of the pollinia— Perfect adaptation of the parts in Orchis pyra- midalis— Other species of Orchis and of some closely allied genera —On the insects which visit the several species, and on the frequency of their visits—On the fertility and sterility of various Orchids—On the secretion-of nectar, and on insects being-purposely delayed in obtaining it .. .. .. «+. 6-44 CHAPTER IL. OPHRER—continued, Fly and Spider Ophrys— Bee Ophrys, apparently adapted for perpetual self-fertilisation, but with paradoxical contrivances for intercrossing —Herminium monorchis, attachment of the pol- linia to the front legs of insects — Peristylus viridis, fertilisation indirectly effected by nectar secreted from three parts of the labellum—Gymnadenia conopsea, and other species—Habenaria or Platanthera chlorantha and bifolia, their pollinia attached to the eyes of Lepidoptera— Other species of Habenaria — Bonatea — Disa — Summary on the powers of movement in the pollinia 45-79 xii CONTENTS, CHAPTER IIlL ARETHUSESX. Cephalanthera grandiflora; rostellum aborted; early penetration of the pollen-tabes; case of imperfect self-fertilisation; cross- fertilisation effected by insects which gnaw the labellum — Cephalanthera ensifolia — Pogonia — Pterostylis and other Australian orchids with the labellum sensitive to a touch — Vanilla—Sobralia .. .. «2 ewe we Swe Pages 80-92 CHAPTER IV. NEOTTER. Epipactis palustris; curious shape of the labellum and its import- ance in the fructification of the flower — other species of Epi- pactis—Epipogium—Goodyera repens—Spiranthes autumnalis ; perfect adaptation by which the ‘pollen of a younger flower is carried to the stigma of an older flower on another plant— Listera ovata; sensitivencss of the rostellum; explosion of viscid matter; action of insects; perfect adaptation of the several organs — Listera cordata—Neottia nidus-avis; its fertilisation effected in the same manner as in Listera—Thely- mitra, self-fertile .. .. 0 .. «1 02 ae we! oe ©9127 CHAPTER V. MALAXEZ AND EPIDENDREZ. Malaxis paludosa— Masaevallia, curious closed flowers —Bolbo- phyllum, labellum kept in constant movement by every breath of air — Dendrobium, contrivance for self-fertilisation—Cattleya, simple manner of fertilisation — Epidendrum—Self-fertile Epi- dendres oo oe te wet cee we we 128~148 CONTENTS. xiii CHAPTER VI. VANDER. Structure of the column and pollinia — Importance of the elasticity of the pedicel; its power of movement — Elasticity and strength of the caudicles— Calanthe with lateral stigmas, manner of fertilisation—Angracum sesquipedale, wonderful length of nec- tary —Species with the entrance into the stigmatic chamber much contracted, so that the pollen-masses can hardly be inserted — Coryanthes, extraordinary manner of fertilisation Pages 149-177 CHAPTER VIL VANDER continued,—CATASETIDZE, Catasetide, the most remarkable of all Orchids—The mechanism by which the pollinia of Catasetum are ejected to a distance and are transported by insects— Sensitiveness of the horns of the rostellum — Extraordinary difference in the male, female, and hermaphrodite forms of Catasetum tridentatum — Mormodes ignea, curious structure of the flowers; ejection of the pollinia —Mormodes luxata—Cycnoches ventricosum, manner of fer- tilisation ie cde” ae Was: GeO wet, “Bay wid) te SEIBS225 CHAPTER VIII. CYPRIPEDEEZ—HOMOLOGIES OF THE FLOWERS OF ORCHIDS, Cypripedium, differs much from all other Orchids — Labellum in the form of a slipper with two small orifices by which insects can escape — Manner of fertilisation by small bees of the genus Andrena—Homological nature of the several parts of the flowers of the Orchidess— Wonderful amount of modification which they have undergone .. 2. 0o oe oe we we 226-246 xiv OONTENTS, CHAPTER IX, GRADATION OF ORGANS, &C.—CONCLUDING REMARKS, Gradation of organs, of the rostellum, of the pollen-masses — Formation of the caudicle— Genealogical affinities — Secretion of nectar — Mechanism of the movement of the pollinia — Uses of the petals—Production of seed—Importance of trifling details of structure — Cause of the great diversity of structure in the flowers of Orchids—Cause of the perfection of the con- trivances — Summary on insect-agency — Nature abhors per- petual self-fertilisation co ee ot we we Page 247-293 12. 13. 14, 15. 16. 17. 18, 19. 20. 21. 22, 23, 24, 25. LIST OF WOODCUTS. ORCHIS MASCULA., .. .. 55 » POLLINIA OF ORCHIS PYRAMIDALIS.. .. Mortu’s HEAD AND PROBOSCIS, WITH ATTACHED OPHRYS MUSCIFERA .. .. a ARANIFERA .. «. y ARACHNITES .. .. + APIFERA., «se PERISTYLUS VIRIDIS .... GYMNADENIA CONOPSEA .. HaBENARIA CHLORANTHA «. PoLLINIA OF HABENARIA CHLORANTHA AND CEPHALANTHERA GRANDIFLORA PTEROSTYLIS LONGIFOLIA ., EPIPACTIS PALUSTRIS... .. 35 LATIFOLIA.. .. SPIRANTHES AUTUMNALIS .. LisTeRA OVATA .. ww we MALAXIS PALUDOSA .. .. MasDEVALLIA FENESTRATA DENDROBIUM CHRYSANTHUM CATTLEYA .. 0 41 oe os DIAGRAM -ILLUSTRATIVE OF THE VANDEE PoLLINIA OF VANDEZ .. PoLLINIuM oF ORNITHOCEPHALUS oe POLLINIA oF 101 107 116 130 136 189 144 150 154 160 xvi LIST OF WOODCUTS. PAGE 26. CALANTHE MASUCA ..0 .. se ee ose ewe LL 27, CoRYANTHES SPECIOSA ee cake ae we. Gee, een LT i 182 og, PoatAsD TUN SACCATUM : es 80. CATASETUM TRIDENTATUM wae we wy we caw OA 381. MonacHaNnTHuUs AND MyantTous .. .. .. « «o 199 32. MoRMODES IGNEA Wai. Ge Seo ai ga Gee Leg 209 33. CYCNOCHES VENTRICOSUM .. .. 16 08 os ee we DDD 34, 5 o* SECTION THROUGH BUD... .. 223 35. CyPRIPEDIUM Mo ee i ae ewe ws, 227 86. TRANSVERSE SECTION OF FLOWER OF AN ORCHID 286 87. RosTeELLUM OF CATASETUM 4... «2 os « « 256 38. Disco oF GYMNADENIA CONOPSEA .. «sees 27D P.S.—I am much indebted to Mr. G. B. Sowerby for the pains which he has taken in making the Diagrams as intelligible as possible. ON THE FERTILISATION OF ORCHIDS BY INSECTS, &e, &e. INTRODUCTION. TuE object of the following work is to show that the contrivances by which Orchids are fertilised, are as varied and almost as perfect as any of the most beauti- ful adaptations in the animal kingdom ; and, secondly, to show that these contrivances have for their main object the fertilisation of the flowers with pollen brought by insects from a distinct plant. In my volume ‘ On the Origin of Species’ I gave only general reasons for the belief that it is an almost universal law of nature that the higher organic beings require an occasional cross with another individual ; or, which is the same thing, that no hermaphrodite fertilises itself for a perpetuity of generations. Having been blamed for propounding this doctrine without giving ample facts, for which I had not sufficient space in that work, J wish here to show that I have not spoken without having gone into details. I have been led to publish this little treatise sepa- rately, as it is too large to be incorporated with any other subject. As Orchids are universally acknow- ledged to rank amongst the most singular and most 2 INTRODUCTION. modified forms in the vegetable kingdom, I have thought that the facts to be given might lead some observers to look more curiously into the habits of our several native species. An examination of their many beautiful contrivances will exalt the whole vegetable kingdom in most persons’ estimation. J fear, however, that the necessary details are too minute and complex for any one who has not a strong taste for Natural History. This treatise affords me also an opportunity of attempting to show that the study of organic beings may be as interesting to an observer who is fully con- vinced that the structure of each is due to secondary laws, as to one who views every trifling detail of structure as the result of the direct interposition of the Creator. I must premise that Christian Konrad Sprengel, in his curious and valuable work, ‘ Das entdeckte Geheim- niss der Natur,’ published in 1793, gave an excellent outline of the action of the several parts in the genus Orchis; for he well knew the position of the stigma, and he discovered that insects were necessary to remove the pollen-masses.* But he overlooked many curious contrivances,—a consequence, apparently, of his belief that the stigma generally receives pollen from the same flower. Sprengel, likewise, has partially described the structure of Epipactis; but in the case of Listera he entirely misunderstood the remarkable phenomena characteristic of that genus, which has been well de- scribed by Dr. Hooker in the ‘ Philosophical Trans- * Delpino has found (‘ Ult. Os- servazioni sulla Dicogamia,’ Part ii. 1875, p. 150) a memoir by Waet- cher, published in 180] in Roe- mer’s ‘ Archiv fiir die Botanik,’ t. ii. p. 11, which apparently has re- mained unknown to everyone else. In this memoir Waetcher, who does not seem to have been ac- quainted with Sprengel’s work, shows that insects are necessary for the fertilisation of various orchids, and describes well the wonderful structure of Necttia. INTRODUCTION. 3 actions’ for 1854. Dr. Hooker has given a full and accurate account, with drawings, of the structure of the parts ; but from not having attended to the agency of insects, he did not fully understand the object gained. Robert Brown,* in his celebrated paper in the ‘ Linnean Transactions,’ expresses his belief that insects are necessary for the fructification of most Orchids; but adds, that the fact of all the capsules on a dense spike not infrequently producing seed, seems hardly reconcilable with this belief: we shall hereafter find that this doubt is groundless. Many other authors have given facts and expressed their belief, more or less fully, on the necessity of insect-agency in the fertilisation of Orchids. In the course of the following work I shall have the pleasure of expressing my deep obligation to several gentlemen for their unremitting kindness in sending me fresh specimens, without which aid this work would have been impossible. The trouble which several of my kind assistants have taken has been extraordinary : I have never once expressed a wish for aid or for in- formation which has not been granted me, as far as possible, in the most liberal spirit. EXPLANATION OF TERMS. In case any one should look at this treatise who has never attended ta Botany, it may be convenient to explain the meaning of the common terms used. In most flowers the stamens, or male organs, surround in a ring the one or more female organs, called the pistils. In all common Orchids there is only one well-developed stamen, which is confluent with the pistils, and they * ‘Linnean Transactious,’ 1833, vol. xvi. p. 704. 4 IN IRODUCTION. form together the column. Ordinary stamens consist of a filament, or supporting thread (rarely seen in British Orchids), which carries the anther; and within the anther lies the pollen or male vivifying element. The anther is divided into two cells, which are very distinct in most Orchids, so much so as to appear in some species like two separate anthers. The pollen in all common plants consists of fine granular powder: but in most Orchids the grains cohere in masses, which are often supported by a very curious appendage, called the caudicle. This part and all the other organs will hereafter be more fully described and figured under the head of the first species, Orchis mascula. The pollen- masses, with their caudicles and other appendages, are called the pollinia. Orchids properly have three pistils or female organs, united together, the upper and anterior surfaces of two of which form the two stigmas. But the two are often completely confluent, so as to appear as one. The stigma is penetrated in the act of fertilisation by long tubes, emitted by the pollen-grains, which carry the contents of the grains down to the ovules or young seeds in the ovarium. The upper stigma is modified into an extraordinary organ, called the rostellum, which in many Orchids presents no resemblance to a true stigma. When mature it either includes or is altogether formed of viscid matter. In many species the pollen-masses are firmly attached to a portion of the exterior membrane, which, when insects visit the flowers, is removed, together with the pollen-masses. This removable portion consists in most British Orchids merely of a small piece of membrane, with a layer or ball of viscid matter underneath, and I shall call it the “ viscid dise;” but in many exotic specics the portion removed is so INTRODUCTION. 5 large and so important, that one part must be called, as before, the viscid disc, and the other part the pedicel of the rostellum, to the end of which the pollen-masses are attached. Authors have called that portion of the rostellum which is removed, the “gland” or “ retina- culum,” from its apparent function of retaining the pollen-masses in their places. The pedicel, or pro- longation of the rostellum, to which in many exotic species the pollen-masses are attached, seems generally to have been confounded, under the name of caudicle, with the true caudicle of the pollen-masses, though their nature and origin are totally different. ‘The part of the rostellum which is left after the removal of the discs and viscid matter, is sometimes called the “bursicula,” or “fovea,” or “pouch.” But it will be found convenient to avoid all these terms, and to call the whole modified stigma the rostellum—sometimes adding an adjective to define its shape; that portion of the rostellum which is removed with the pollen- masses being called the viscid dise, together in some cases with the pedicel. Lastly, the three outer divisions of the flower arc called sepals, and form the calyx; but, instead of being green, as in most common flowers, they are generally coloured, like the three inner divisions or petals of the flower. In almost all the species, one of the petals, which is properly the upper one, is larger than the others and stands on the lower side of the flower, where it offers a landing-place for insects, having been carried round by the twisting of the ovarium. It is called the lower lip or lubellum, and often assumes most singular shapes. It secretes nectar for the sake of attracting insects, and is often produced into a spur- like nectary. 6 OPHRES. Cuar. I. CHAPTER I. OPHREZ. Structure éf the flower of Orchis mascula—Power of movement of the pollinia— Perfect adaptation of the parts in Orchis pyramidalis— Other species of Orchis and of some closely allied genera—On the insects which visit the several species, aid on the frequency of their visits—On the fertility and sterility of various Orchids—On the secretion of ncctar and on insects being purposely delayed in obtaining it. Turoucuout the following volume I have followed, as far as I conveniently could, the arrangement of the Orchidee given by Lindley. The British species belong to five of his tribes, the Ophrex, Neottez, Arethusee, Malaxee and Cypripedex, but the two latter tribes contain each only a single genus. Various British and foreign species belonging to the several tribes are described in the first eight chapters. The eighth also contains a discussion on the homologies of the flowers of the Orchidew. The ninth chapter is devoted to miscellaneous and general considerations. The Ophres include most of our common British species, and we will begin with the genus Orchis. The reader may find the following details rather difficult to understand; but I can assure him, if he will have patience to make out the first case, the succeeding ones will be easily intelligible. The accompanying diagrams (fig. 1, p. 8) show the relative position of the more important organs in the flower of the Early Orchis (O. mascula). The sepals and the petals have been re- moved, excepting the labellum with its nectary. The Onar, 1. ORCHIS MASCULA. it nectary is shown only in the side view (n, fig. A); for its enlarged orifice is almost hidden in shade in the front view (B). The stigma (s) is bilobed, and con- sists of two almost confluent stigmas; it lies under the pouch-formed rostellum (r). The anther (a, in B and A) consists of two rather widely separated cells, which are longitudinally open in front: each cell includes a pollen-mass or pollinium. A pollinium removed out of one of the two anther- cells is represented by fig. C; it consists of a number of wedge-formed packets of pollen-grains (see fig. F, in which the packcts are forcibly separated), united together by excessively elastic, thin threads. These threads become confluent at the lower end of each pollen-mass, and compose the straight elastic caudicle (e, C). The end of the caudicle is firmly attached to the viscid disc (d, C), which consists (as may be seen in the section of the pouch-formed rostellum, fig. E) of a minute oval piece of membrane, with a ball of viscid matter on its under side. Each pollinium has its separate disc; and the two balls of viscid matter lie enclosed together (fig. D) within the rostellum. The rostellum is a nearly spherical, somewhat pointed projection (r, figs. A and B) overhanging the two almost confluent stigmas, and must be fully de- scribed, as every detail of its structure is full of signi- ficance. A section through one of the discs and balls of viscid matter is given (fig. E); and a front view of both viscid dics within the rostellum (fig. D) is like- wise given. This latter figure (D) probably best serves to explain the structure of the rostellum; but it must be understood that the front lip is here con- siderably depressed. The lowest part of the anther is united to the back of the rostellum, as may be seen in fig. B. At an early period of growth the rostellum Cuar. I. OPHRE.E, Fig. 1. OncHIS MASCULA Caar. I. ORCHIS MASCULA. 9 DeEscRirTIon oF Fic. 1, a, anther, consisting of two cells. *”. nectary. r. rostellum, p» pollen-mass, 8. stigma. o. caudicle of pollinium, 1. labellum. d. viscid disc of pollinium, A. Side view of flower, with all the petals and sepals cut off except the labellum, of which the near half is cut away, as well as the upper portion of the near side of the nectary. B. Front view of flower, with all sepals and petals removed, except the labellum. One pollinium, showing the packets of pollen-grains, the caudicle, and viscid disc. D. Front view of the caudicles of both pollinia with the discs lying within © the rostellum, its lip being depressed. E. Section through one side of the rostellum, with the included disc and eaudicle of one pollinium, lip not depressed. F. Packets of pollen-grains, tied together by elastic threads, here extcuded. (Copied from Bauer.) Q JU OPHREZ. Cae. L. consists of a mass of polygonal cells, full of brownish matter, which cells soon resolve themselves into two balls of extremely viscid semi-fluid matter, void of structure. These viscid masses are slightly elongated, almost flat on the top, and convex below. They lie quite free within the rostellum (being surrounded by fluid), except at the back, where each viscid ball adheres to a small portion or disc of the exterior membrane of the rostellum. The ends of the two caudicles are strongly attached externally to these two little discs of membrane. The membrane forming the whole exterior surface of the rostellum is at first continuous; but:as soon as the flower opens the slightest touch causes it to rupture transversely in a sinuous line, in front of the anther- cells and of the little crest or fold of membrane (see fig. D) between them. This act of rupturing makes no difference in the shape of the rostellum, but con- verts the front part into a lip, which can be depressed. easily. This lip is represented considerably depressed in fig. D, and its edge is seen, fig. B, in the front view. When the lip is thoroughly depressed, the two balls of viscid matter are exposed. Owing to the elasticity of the hinder part, the lip or pouch, after being pressed down, springs up again and encloses the two viscid balls. I will not affirm that the rupturing of the exterior membrane of the rostellum never takes place sponta- neously ; and no doubt the membrane is prepared for rupture by having become very weak along defined lines; but several times I saw the act ensue from an excessively slight touch—so slight that I conclude that the action is not simply mechanical, but, for the want of a better term, may be called vital. We shall hereafter meet with other cases, in which the slightest Cuap. L ORCHIS MASCULA. 11 touch or the vapour of chloroform causes the exterior membrane of the rostellum to rupture along certain defined lines. At the same time that the rostellum. becomes trans- versely ruptured in front, it probably (for it was impossible to ascertain this fact from the position of the parts) ruptures behind ‘in two oval lines, thus separating and freeing from the rest of the exterior surface of the rostellum the two little discs of mem- brane, to which the two caudicles are attached exter- nally, and to which the two balls of viscid matter adhere internally. The line of rupture is thus very complex, but strictly defined. As the two anther-cells are open longitudinally in front from top to bottom, even before the flower expands, it follows that as soon as the rostellum is properly ruptured from the effects of a slight touch, its lip can be depressed easily, and, the two little discs of membrane being already separate, the two pollinia now lie absolutely free, but are still embedded in their proper places. So that the packets of pollen and the caudicles still lie within the anther-cells; the discs still form part of the rostellum, but are separate; and the balls of viscid matter still lie concealed within the rostellum. Now let us see in the case of Orchis mascula (fig. 1) how this complex mechanism acts. Suppose an insect to alight on the labellum, which forms a good landing- place, and to push its head into the chamber (see side view, A, or front view, B), at the back of which lies the stigma (s), in order to reach with its proboscis the end of the nectary; or, which does equally well to show the action, push very gently a sharply-pointed common pencil into the nectary. Owing to the pouch-formed rostellum projecting into the gangway of the nectary, 12 OPHRES. Cuar. I. it is scarcely possible that any object can be pushed into it without the rostellum being touched. The ex- terior membrane of the rostellum then ruptures in the proper lines, and the lip or pouch is easily depressed. When this is effected, one or both of the viscid balls will almost infallibly touch the intruding body. So viscid are these balls that whatever they touch they firmly stick to. Moreover the viscid matter has the peculiar chemical quality of setting, like a cement, hard and dry in a few minutes’ time. As the anther-cells are open in front, when the insect with- draws its head, or when the pencil is withdrawn, one pollinium, or both, will be withdrawn, firmly cemented to the object, projecting up like horns, as shown (fig. 2) Fig. 2. A. Pollen-mass of 0. mascula, when | B. Pollen-mass of O. mascula, after first attached, the act of depression. by the upper figure, A. The firmness of the attach- ment of the cement is very necessary, for if the pollinia were to fall sideways or backwards they could never fertilise the flower. From the position in which the two pollinia lie in their cells, they diverge a little when attached to any object. Now suppose that the insect flies to another flower, or let us insert the pencil. (A, fig. 2\, with the attached pollinium, into a Cuar. L. ORCHIS MASCULA. 13 the same or into another nectary: by looking at the diagram (fig. 1, A) it will be evident that the firmly attached pollinium will be simply pushed against or into its old position, namely, into the anther-cell. How then can the flower be fertilised? This is effected by a beautiful contrivance: though the viscid surface remains immovably affixed, the apparently insignificant and minute disc of membrane to which the caudicle adheres is endowed with a remarkable power of contraction (as will hereafter be more minutely described), which causes the pollinium to sweep through an angle of about ninety degrees, always in one direction, viz., towards the apex of the proboscis or pencil, in the course of thirty seconds on an average. The position of the pollinium after the movement is shown at B in fig. 2. After this movement, completed in an interval of time which would allow an insect to fly to another plant,* it will be seen, by turning to the diagram (fig. 1, A), that, if the pencil be inserted into the nectary, the thick end of the pollinium now exactly strikes the stigmatic surface. Here again comes into play another pretty adapta- tion, long ago noticed by Robert Brown.t The stigma is very viscid, but not so viscid as when touched by a pollinium to pull the whole off an insect’s head or off a pencil, yet sufficiently viscid to break the elastic threads (fig. 1, F) by which the packets of pollen-grains are tied together, and leave some of them on the stigma. Hence a pollinium attached to an insect or to a pencil can be applied to many stigmas, and will fertilise all. I have often seen the * Dr. H. Miiller (‘Die Befruch- flowers of Orchis mascula, and tung der Blumen durch Insekten,’ _ finds that this statement is correct. 1878, p. 84) has timed humble- + ‘ Transactionsof the Linnean bees at work on the spikes of Society,’ vol. xvi. p. 731. 14 OPHRE. Cuap. L pollinia of Orchis pyramidalis adhering to the pro- boscis of a moth, with the stump-like caudicles alone left, all the packets of pollen having been left glued to the stigmas of the successively visited flowers. One or two other little points must be noticed. The balls of viscid matter within the pouch-formed rostellum are surrounded with fluid; and this is very important, for, as already mentioned, the viscid matter sets hard when exposed to the air for a very short time. I have pulled the balls out of their pouches, and found that they had entirely lost the power of adhesion after a few minutes. Again, the little discs of membrane, the movement of which, as causing the movement of the pollinia, is so abso- lutely indispensable for the fertilisation of the flower, lie at the upper and back surface of the rostellum, and are closely enfolded and thus kept damp within the bases of the anther-cells; and this is very neces- sary, as an exposure of about thirty seconds causes the movement of depression to take place; but as long as the disc is kept damp, the pollinia remain ready for action whenever removed by an insect. Lastly, as I have shown, the pouch, after being depressed, springs up to its former position; and this is likewise of great service; for if this action did not take place, and an insect after depressing the lip failed to remove the two viscid balls, or if it removed one alone, then in the first case both, and in the second case one would be left exposed to the air; consequently one or both would quickly lose all adhesiveness, and the pollinium would be rendered ab- solutely useless. That with many kinds of Orchids insects often remove only one of the two pollinia at a time is certain; it is even probable that they generally remove only one, for the lower and older Cuar. L ORCHIS. 15 flowers almost always have both pollinia removed, whilst the younger flowers close beneath the buds, which will have been seldomer visited, have frequently only one pollinium removed. In a spike of Orchis maculata, I found as many as ten flowers, chiefly the upper ones, which had only one pollinium removed ; the other pollinium being still in its proper place with the lip of the rostellum well closed up; so that all the mechanism was perfect for its subsequent removal by some other insect. When the first edition of this book was published, I had not seen any insects visiting the flowers of the present species; but a friend watched some plants, and saw them visited by several humble-bees, appa- rently Bombus muscorum ; and Dr. H. Miller * has seen four other species of Bombus at work. He caught ninety-seven specimens, and of these thirty-two had pollinia attached to their heads. The description now given of the action of the organs in Orchis mascula applies to O. morio, fusca, maculata, and latifolia. These species present slight and apparently co-ordinated differences in the length of their caudicles, in the direction of the nectary, in the shape and position of the stigma, but they are not worth detailing. In all, the pollinia when removed from the anther-cells undergo the curious movement of depression, which is so necessary to place them in a right position on an insect’s head for striking the stigmatic surface of another flower. Six species of humble-bees, the hive-bee and two other kinds have been seen by H. Miller and myself visiting the flowers of Orchis morio. On some of the * ‘Die Befruchtung, &c., p. 84 16 OPUREZ. Cuar. L hive-bees from ten to sixteen pollen-masses adhered ; to the head of Eucera longicornis eleven, to the head of Osmia rufa several, and several to the bare surface close above the mandibles of Bombus muscorum. H. Miller has seen twelve different kinds of bees visiting the flowers of 0. latifolia, which are also visited by Diptera. My son George observed for some time plants of O. maculata, and saw many specimens of a fly (Empis livida) inserting their proboscides into the nectary; and subsequently the same fact was ob- served by me. He brought home six specimens of this Empis, with pollinia attached to their spherical eyes, on a level with the bases of the antennz. The pollinia had undergone the movement of depression, and stood a little above and parallel‘to the proboscis: hence they were in a position excellently adapted to strike the stigma. Six pollinia were thus attached to one specimen, and three to another. My son also saw another and smaller species (Empis pennipes) inserting its proboscis into the nectary; but this species did not act so well or so regularly as the other in fertilising the flowers. One specimen of this latter Empis had five pollinia, and a second had three pollinia, attached to the dorsal surface of its convex thorax. H. Miller has seen two other genera of Diptera at work on this orchis, with pollinia attached to the front part of their bodies; and on one occasion he saw a humble-bee visiting the flowers.* We now come to Orchis (sub-genus, Anacamptis) pyramidalis, one of the most highly organised species * M. M. Girard caught a _ front of its mouth: ‘Annales de longicorn beetle, Strangalia atra, la Soc. Entomolog. de France,’ with a tuft of the pollen-masses tom ix. 1869, p. xxxi. of this orchis attached to the Cuar. 1 ORCHIS PYRAMIDALIS. 17 which I have examined, and which is ranked by several botanists as a distinct genus. The relative position of the parts (fig. 3) is here considerably different from what it is in O. mascula and its allies. There are two quite distinct rounded stigmatic surfaces (s, s, A) placed on each side of the pouch-formed rostellum. This latter organ, instead of standing some height above the nectary, is brought down (see side view B) so as to overhang and partially to close its orifice. The ante-chamber to the nectary, formed by the union of the edges of the labellum to the column, which is large in O. mascula and its allies, is here small. The pouch-formed rostellum is hollowed out on the under side in the middle: it is filled with fluid. The viscid disc is single and of the shape of a saddle (figs. C and E); it carries on its nearly flat top or seat the two caudicles of the pollinia, the ends of which firmly adhere to its upper surface. Before the membrane of the rostellum ruptures, the saddle- formed disc can be clearly seen to be coutinuous with the rest of the surface. The disc is partially hidden and kept damp (which is of great iraportance) by the over-folding bases of the two anther-cells. It consists of several layers of minute cells, and is therefore rather thick; it is lined beneath with a layer of highly ad- hesive matter, which is formed within the rostellum. It corresponds strictly to the two minute, oval, sepa- rate discs to which the two caudicles of O. mascula and its allies are attached. When the flower opens and the rostellum has become symmetrically ruptured, either from a touch or spontaneously (I know not which), the slightest pressure depresses the lip, that is, the lower and bi- lobed portion of the exterior membrane of the ros- tellum, which projects into the mouth of the nectary. 18 OPHREZ., Fig. 3. Cuar. [. ORcHIs PYRAMIDALIS. Crap. I. ORCHIS PYRAMIDALIS. 19 DeEscrirtTion or Fia. 3. a, anther. “| @ labellum. 8,8. stigma. 1’, guiding plate on the labellum, r. rostellum. nm. nectary. A. Front view, with all the sepals and petals removed, except the labellum. B. Side view, with all the sepals and petals removed, with the labellum longitudinally bisected, and with the near side of the upper part of the nectary cut away. C. The two pollinia attached to the saddle-shaped viscid disc, D. The dise after the first act of contraction, with no object seized, E. The disc seen from above, and flattened by force, with one pollinium removed; showing a depression in its surface, by which the second movement of the pollinium is effected. F, The pollinia removed by the insertion of a needle into the nectary, after the saddle has clasped the needle by the first act of contraction. G. The same pollinia after the second movement and their consequent depression. 20 OPHRES. Car. L. When the lip is depressed, the under and viscid surface of the disc, still remaining in its proper place, is un- covered, and is almost certain to adhere to the touch- ing object. Even a human hair, when pushed into the nectary, is stiff enough to depress the lip or pouch ; and the viscid surface of the saddle adheres to it. If, however, the lip be pushed only slightly, it springs back and recovers the under side of the saddle. The perfect adaptation of the parts is well shown by cutting off the end of the nectary and inserting a bristle at that end; consequently in a reversed direc- tion to that in which moths insert their proboscides ; and it will be found that the rostellum may easily be torn or penetrated, but that the saddle is rarely or never caught. When the saddle together with the pollinia is removed on a bristle, the under lip in- stantly curls closely inwards, and leaves the orifice of the nectary more open than it was before; but whether this is of much service to the moths which frequent the flowers, and consequently to the plant, I will not pretend to decide. Lastly, the labellum is furnished with two pro- minent ridges (I, figs. A, B), sloping down to the middle and expanding outwards like the mouth of a decoy; these ridges serve to guide any flexible body, like a fine bristle or hair, into the minute and rounded orifice of the nectary, which, small as it already is, is partly choked up by the rostellum. This contrivance of the guiding ridges may be com- pared to the little instrument sometimes used for guiding a thread into the fine eye of a needle. Now let us see how these parts act. Let a moth insert its proboscis (and we shall presently see how frequently the flowers are visited by Lepidoptera) Cuar. I. ORCHIS PYRAMIDALIS. 21 between the guiding ridges of the labellum, or insert a fine bristle, and it is conducted safely to the minute orifice of the nectary, and can hardly fail to depress the lip of the rostellum; this being effected, the bristle comes into contact with the now naked and sticky under surface of the suspended saddle-formed disc. When the bristle is removed, the saddle with the attached pollinia is removed. Almost instantly, as soon as the saddle is exposed to the air, a rapid movement takes place, and the two flaps curl inwards and embrace the bristle. When the pollinia are pulled out by their caudicles, by a pair of pincers, so that the saddle has nothing to clasp, I observed that the flaps curled inwards so as to touch each other in nine seconds (see fig. D), and in nine more ‘seconds the saddle was converted by the flaps curl- ing still more inwards into an apparently solid ball. The proboscides of the many moths which I have examined, with the pollinia of this Orchis attached to them, were so thin that the tips of the flaps just met on the under side. Hence a naturalist, who sent me a moth with several saddles attached to its proboscis, and who did not know of this movement, very naturally came to the extraordinary conclusion that the moth had cleverly bored through the exact centres of the so-called sticky glands of some Orchid. Of course this rapid clasping movement helps to fix ‘the saddle upright on the proboscis, which is very important ; but the viscid matter setting hard rapidly would probably suffice for this end, and the real object gained by the clasping or curling movement is the divergence of the pollinia. The pollinia, being at- tached to the flat top or seat of the saddle, project at first straight up and nearly parallel to each other; 22 OPHRE. Cuar. I, but as the flat top curls round the cylindrical and thin proboscis, or round a bristle, the pollinia neces- sarily diverge. As soon as the saddle has clasped the bristle and the pollinia have diverged, a second move- ment commences, which action, like the last, is ex- clusively due to the contraction of the saddle-shaped disc of membrane, as will be more fully described in the ninth chapter. This second movement is the same as that in O. mascula and its allies, and causes the divergent pollinia, which at first projected at right angles to the.needle. or bristle (see fig. F), to sweep through an angle of nearly ninety degrees towards the tip of the needle (see fig. G), so as to become de- pressed and finally to lie in the same plane with the needle. In three specimens, this second movement was effected in from thirty to thirty-four seconds after the removal of the pollinia from the anther-cells, and therefore in about fifteen seconds after the saddle had clasped the bristle. The use of this double movement becomes evident if a bristle with pollinia attached to it, which have diverged and become depressed, be pushed between the guiding ridges of the labellum into the nectary of the same or another flower (compare figs. A and G); for the two ends of the pollen-masses will be found now to have acquired such a position that the end of the one strikes against the stigma on the one side, and the end of the other at the same moment strikes against the stigma on the opposite side. The secretion on the stigmas is so viscid that when the pollinia are withdrawn, the elastic threads by which the packets of pollen are bound together are ruptured ; and some dark-green grains may be seen, even by the naked eye, remaining on the two white stigmatic sur- faces. I have shown this little experiment to several Cuar. I. ORCHIS PYRAMIDALIS. 23 persons, and all have expressed the liveliest admiration at the perfection of the contrivance by which this Orchid is fertilised. As in no other plant, or indeed in hardly any animal, can adaptations of one part to another, and of the whole to other organisms widely remote in the scale of nature, be named more perfect than those presented by this Orchis, it may be worth while briefly to sum them up. As the flowers are visited both by day and night-flying Lepidoptera, it is not fanciful to believe that the bright-purple tint (whether or not specially developed for this purpose) attracts the day-fliers, and the strong foxy odour the night- fliers. The upper sepal and two upper petals form a hood protecting the anther and stigmatic surfaces from the weather. The labellum is developed into a long nectary in order to attract Lepidoptera, and we shall presently give reasons for suspecting that the nectar is purposely so lodged that it can be sucked only slowly (very differently from what occurs in most other plants), in order to give time for the viscid matter on the under side of the saddle to set hard and dry. He who will insert a fine and flexible bristle into the expanded mouth of the flower between the sloping ridges on the labellum, will not doubt that they serve as guides and effectually prevent the bristle or proboscis from being inserted obliquely into the nectary. This latter circumstance is of manifest importance, for, if the proboscis were inserted ob- liquely, the saddle-formed dise would become attached obliquely, and after the compounded movement of the pollinia they would not strike the two lateral stigmatic surfaces. Then we have the rostellum partially closing the mouth of the nectary, like a trap placed in a run for 24 OPHREA‘ Cuap. 1 game; and the trap so complex and perfect, with its symmetrical lines of rupture forming the saddle- shaped disc above, and the lip of the pouch below; and, lastly, this lip so easily depressed that the pro- boscis of a moth can hardly fail to uncover the viscid disc and adhere to it. But if this fails to occur, the elastic lip rises and covers again the viscid surface, so as to keep it damp. The viscid matter within the rostellum is attached to the saddle-shaped disc alone, and is surrounded by fluid, so that it does not set hard till the disc is withdrawn. The upper surface of the saddle, with the attached caudicles, is also kept damp by the bases of the anther-cells, until it is withdrawn, and then the curious clasping movement instantly commences, causing the pollinia to diverge, followed by the movement of depression, which move- ments together are exactly fitted to cause the ends of the two pollen-masses to strike the two stigmatic surfaces. These stigmatic surfaces are not so sticky as to tear off the whole pollinium from the proboscis of the moth, but by rupturing the elastic threads to secure a few packets of pollen, leaving plenty for other flowers.* _ But let it be observed that, although the moth pro- bably takes a considerable time to suck the nectar of a flower, yet the movement of depression in the pol- linia does not commence (as I know by trial) until they are fully withdrawn ; nor will the movement be completed, and the pollinia properly placed for strik- ing the stigmatic surfaces, until about half a minute has elapsed, which will give ample time for the moth to * The late Prof. Treviranushas but points out two unimportant confirmed (‘Botanische Zeitung,’ inaccuracies in the drawing which 1863, p. 241) all my observations, I have given, Cuar. 1 ORCHIS USTULATA. 25 fly to another plant, and thus effect a union between two distinct individuals. Orchis ustulata* resembles O. pyramidalis in some important respects, and differs from it in others. The labellum is deeply channelled, and the channel which replaces the guiding ridges of O. pyramidalis leads to the small triangular orifice of the short nectary. The upper angle of the triangle is overhung by the ros- tellum, the pouch of which is rather pointed below. In accordance with this position of the rostellum, close to the mouth of the nectary, the stigma is double and lateral. This species shows in an interest- ing manner how easily two distinct stigmas, like those of O. pyramidalis, might be converted into a single one, by becoming at first slightly lobed like that of O. mascula, and then acquiring its present structure. For directly beneath the rostellum there is a narrow transverse rim, formed of true stigmatic tissue, which connects together the two lateral stigmas; so that if this rim were widened, the two stigmas would be converted into a single transverse one. Conversely a single stigma might thus easily be converted into a double one. The pollinia undergo the usual move- ment of depression, and in acquiring this position the two diverge slightly, so as to be ready to strike the two lateral stigmas. Orchis (sub-genus Himantoglossum) hircina.—A. fine specimen of this extremely rare British plant, the Lizard Orchis, with its curious elongated labellum, was sent me by Mr. Oxenden. The two pollinia arise from a single almost square disc; and when * Tam greatly indebted to Mr. kindness in supplying me with G. Chichester Oxenden of Broome __ living plants, and information re- Park for fresh specimens of this garding many of the rarer Britisn Orchis, and for his never-tiring Orchids. 26 OPHREZ. Cuap. L they are removed from their cells, they do not di- verge, but become depressed, sweeping through an angle of ninety degrees, in about thirty seconds. They are then in a proper position for striking the single large stigma which lies beneath the rostellum. In the case of O. pyramidalis we have seen that the depression of the two pollinia is effected by the contraction of -the disc in front of each, two furrows or valleys being there formed; whilst with the present species, the whole front of the disc contracts or sinks down, the {ront part being thus separated from the hinder part -by an abrupt step. Aceras* (Orchis) anthropophora.—The caudicles of the pollinia are unusually short; the nectary consists of two minute rounded depressions in the labellum; the stigma is transversely elongated; and lastly the two viscid discs lie-so close together within the ros- tellum that they affect each other’s outline. This latter fact is worth notice, as a step towards the two becoming absolutely confluent, as in the following species of Aceras, in O. pyramidalis and hireina. Nevertheless, in Aceras a single pollinium is some- times removed by insects, though more rarely than with the other species of Orchis. Aceras (Orchis) longibracteata.—-Mr. Moggridge has given an interesting account, together with a figure, of this plant which grows in the South of France.t The pollinia are attached to a single viscid disc. When they are removed they do not diverge as in O. pyramidalis, but converge and then undergo the * The separation of this genus is evidently artificial. It isa true Orchis, but with a very short nectary. Dr. Weddell has de- scribed (‘Annales des Se. Nat.,’ 3 ser. Bot. tom. xviii. p. 6) the occurrence of numerous hybrids, naturally produced, between this Aceras and Orehis galeata. _¢ ‘Journ. Linn. Soc. Bot,’ vol. viii. 1865, p. 256. He gives also a figure of Orchis hircina. Cuar. I. NIGRITELLA ANGUSTIFOLIA. 27 movement of depression. The most remarkable point about this species is that insects seem to suck nectar out of minute open cells in the honeycombed surface of the labellum. The flowers are visited by various hymenopterous and dipterous insects; and the author saw the pollinia attached to the forehead of a large bee, the Xylocopa violacea. Neotinea (Orchis) intacta.a—Mr. Mogegridge sent me from North Italy living specimens of. this very rare British plant, which, as he informed me, is remark- able from producing seeds without the aid of insects. When insects were carefully excluded by me, almost all the flowers produced capsules. Their fertilisation follows from the pollen being extremely incoherent, so as to fall spontaneously on the stigma. Nevertheless -a short nectary is present, the pollinia possess small viscid discs, and all the parts are so arranged that, if insects were to visit the flowers, the pollen-masses would almost certainly be removed and carried to another flower, but not so effectually as with most other orchids, Serapias cordigera, an inhabitant of the South of France, has been described by Mr. Moggridge in the paper just referred to. The pollinia are attached to a single viscid disc; when first withdrawn, they are bent backwards, but soon afterwards move forwards and downwards in the usual manner. As the stigmatic cavity is narrow, the pollinia are guided into it by two guiding plates. Nigritella angustifolia.—This Alpine species is said by Dr. H. Miller * to differ from all ordinary orchids in the ovarium not being twisted; so that the labellum stands on the upper side of the flower, and insects * ‘Nature,’ Dee. 31, 1874, p. 169. 28 OPHREZ. Cuar. I. alight on the opposite sepals and petals. As a con- sequence of this, when a butterfly inserts its proboscis into the narrow entrance of the nectary, the viscid discs become attached to the lower surface of the proboscis, and the pollinia afterwards move upwards, instead of as in all other orchids downwards. They are then in the proper position for striking the stigma of the next flower which is visited. Dr. Miller remarks that the flowers are frequented by an extraordinary number of butterflies. I have now described the structure of most of the British and of a few foreign species in the genus Orchis and its close allies. All these species, with the exception of the Neotinea, require the aid of insects for their fertilisation. This is obvious from the fact that the pollinia are so closely embedded in the anther-cells, and the ball of viscid matter in the pouch-formed rostellum, that they cannot be shaken out by violence. We have also seen that the pollinia do not assume the proper position for striking the stigmatic surface until some time has elapsed; and this indicates that they are adapted to fertilise, not their own flowers, but those on a distinct plant. To prove that insects are neces- sary for the fertilisation of the flowers, I covered up a plant of Orchis morto under a bell-glass, before any of its pollinia had been removed, leaving three adjoining plants uncovered; I looked at the latter every morning, and daily found some of the pollinia removed, till all were gone with the exception of those in a single flower low down on one spike, and of those in one or two flowers on the summits of all the spikes, which were never removed. Butit should be observed that when only a very few flowers remain open on the summits of the spikes, these are no longer conspicuous, Cuap. L. FERTILISED BY INSECTS. 29 and would consequently be rarely visited by insects. I then looked at the perfectly healthy plant under the bell-glass, and it had, of course, all its pollinia in the anther-cells. I tried an analogous experiment with specimens of 0. mascula with the same result. It de- serves notice that the spikes which had been covered up, when subsequently left uncovered, never had their pollinia carried away by insects, and did not, of course, set any seed, whereas the adjoining plants produced plenty of seed. From this fact it may be inferred that there is a proper season for each kind of Orchis, and that insects cease their visits after the proper season. has’ passed. With many of the hitherto mentioned species, and with several other European kinds, the sterility of the flowers, when protected from the access of insects, depends solely on the pollen-masses not coming into contact with the stigma. This has been proved to be the case by Dr. Hermann Miller, who, as he informs me, applied the pollen-masses of Orchis pyramidalis (44), fusca (6), militaris (14), variegata (3), coriophora (6), morio (4), maculata (18), mascula (6), latifolia (8), incarnata (3), Ophrys muscifera (8), Gymnadenia conop- sea (14), albida (8), Herminium monorchis (6), Epipogon aphyllus (2), Epipactis latifolia (14), palustris (4), Listera ovata (5), and Cypripedium calceolus (2), to their own stigmas, and full-sized capsules, containing seeds in appearance good, were formed. The numbers placed after the names of the species show how many flowers were tried in each case. These facts are remarkable, because Mr. Scott and Fritz Miller* have proved * An abstract of their observa- _ tication, chap. xvii. 2nd edit. vol tions is given in my ‘Variation of ii. p. 114. : Animals and Plants under Domes- 30 OPHREZ. Ouag. L that various exotic species, both in this country and in their native homes, invariably fail to yield seed- capsules, when the flowers are fertilised with their own pollen. From the observations already given, and from what will hereafter be shown with respect to Gym nadenia, Habenaria, and some other species, it is a safe generalisation* that species with a short and not very narrow nectary are fertilised by bees and flies; whilst those with a much elongated nectary, or one having a very narrow entrance, are fertilised by butterflies or moths, these being provided with long and thin proboscides. We thus see that the structure of the flowers of Orchids and that of the insects which habitually visit them, are corre- lated in an interesting manner,—a fact which has been amply proved by Dr. H. Miller to hold good with many of the Orchidee and other kinds of plants. With respect to Orchis pyramidalis, which possesses, as we have seen, an elongated nectary, Mr. Bond was so kind as to send me a large number of Lepidoptera, out of which I selected twenty-three species, enumer- ated in the following list, with the pollinia of this Orchid, which can easily be recognised, attached to their proboscides. * Some remarks to this effect were given in my “Notes on the Fertilisation of Orchids,” in ‘Annals and Mag. of Nat. Hist.’ Sept. 1869, p. 2. + M. Méniére (in ‘Bull. Bot. Soe. de France, tom. i. 1854, p. 370) says he saw in Dr. Guépin’s collection, bees collected at Sau- mur with the pollinia of Orchids attached to their heads; and he states that 1 person who kept bees near the Jardin de la Faculté (at Toulouse?) complained that his bees returned from the garden with their heads charged with yellow bodies, of which they could not free themselves. ‘This is good evidence how firmly the pollinia are attached. There is, however, nothing to show whether the pol- linia in these cases belonged to the genus Orchis or to some other genus of the family. Cuar, I. Polyommatus alexis, Lycena plileas, Arge galathea, Hesperia sylvanus. es linea. Syrichthus alveolus. Anthrocera filipendula, si trifolii.* Lithosia complana. Leucania lithargyria (two speci- mens). Caradrina blanda. es alsines. Agrot's cataleuca, FERTILISED BY INSECTS. 31 Eubolia mensuraria (two speci- mens). Hadena dentina, Heliothis marginata (two speci- mens). Xylophasia sublustris (two speci- mens). Fuclidia glyphica. Toxocampa pastinum, Melanippe rivaria. Spilodes palealis. 5 cinctalis, Acontia luctuosa. A large majority of these moths and butterflies had two or three pairs of pollinia attached to them, and invariably to the proboscis. seven pair (fig. 4), and the Caradrinano lessthaneleven _ pair! The proboscis of this latter moth presented an ex- traordinary arborescent ap- pearance. Thesaddle-formed discs, each bearing a pair of pollinia, adhered to the pro- boscis, one before the other, witn perfect symmetry ; and this follows from the moth having always inserted its The Acoutia had Fig. 4. Head and proboscis of Acontia luc- tuosa with seven pair of pollinia of Orchis pyramidalis attached to the proboscis. proboscis into the nectary in exactly the same manner, owing to the presence of the guiding plates on the labellum. The unfortunate Caradrina, with its pro- boscis thus encumbered, could hardly have reached the extremity of the nectary, and would soon have * Tam indebted to Mr. Parfitt for an examination of tl:is moth, which is mentioned in the ‘En- tomologist’s Weekly Intelligencer,’ vol. ii. p. 182, and vol. iii. p. 3, Oct. 3, 1857, The pollinia were erroneously thought to belong to Ophrys apifera. The pollen had changed from its natural green colour to yellow; on washing it, however, and drying it, the green tint returned, 82 OPHREZ. Cuar. I. been starved to death. Both these moths must have sucked many more than the seven and eleven flowers, of which they bore the trophies, for the earlier at- tached pollinia had lost much of their pollen, showing that they had touched many viscid stigmas. The above list proves that many different species of Lepidoptera visit the same kind of Orchis. The Hadena dentina also frequents Habenaria. Probably all the Orchids provided with elongated nectaries are visited indifferently by many kinds of moths. Whether any of the British Orchids are fertilised exclusively by special insects confined to certain localities is very doubtful ; but we shall hereafter see that Epipactis latifolia seems to be fertilised by wasps alone. I have twice observed plants of Gymnadenia conopsea, which had been transplanted into a garden many miles from its native home, with nearly all their pollinia removed. Mr. Marshall of Ely* has made the same observation on similarly transplanted specimens of O. maculata. On the other hand fifteen plants of Ophrys muscifera had not one pollen-mass there removed. Malazxis paludosa was placed in a bog about two miles from that in which it naturally grew; and it had most of its pollinia immediately removed. The list which follows serves to show that insects in most cases perform the work of fertilisation effectually. But the list by no means gives a fair idea how effectu- ally it is done; for I have often found nearly all the pollinia removed, but kept an exact record only in exceptional cases, as may be seen by the appended remarks. Moreover, in most cases, the pollinia which * ‘Gardener’s Chronicle,’ 1861, marks of mine on this subject p. 73. Mr. Marshall’s communi- _ previously published in the ‘ Gar- cation was in answer to some re- _dener’s Chronicle,’ 1860, p. 528. Cuar, 1. FERTILISED BY INSECTS. 33 had not been removed were in the upper flowers beneath the buds, and many of these would probably have been subsequently carried away. I have often found an abundance of pollen on the stigmas.of flowers which had not their own pollinia removed, showing that they had been visited by insects. In many other cases the pollinia had been removed, but no pollen had been as'yet left on the stigmas. Aaq@ .jageeo ae SESq (2283 [22 BEES EGE | af S3 |os Sock! oF Baas |Sag7=| oe eS S/baeual es a2 gle ecgc|/ as Boek lee Bi 5% s : pole |seueel eed #283 (225 22) 228 £225 |88a88| 22 a 4 a Orchis morio, Three small plants, N. Kent 22 2 6 Orchis morio. Thirty-eight ‘plants. Kent. These plants were in after nearly four weeks of extraordi- om narily alll and wet weather in 1860; oe 23 19 and therefore under the most unfavour- able circumstances. Orchis pyramidalis. Two plants ae 6 Kent and peopel ; : rehis pyramidalis. Six p! ants from a arolevied valleys. Devonshire . 102 ee 66 Orehis pyramidalis, Six plants from | much exposed bank. Devonshire Orchis maculata. One plant. Stafford- shire. Of the twelve flowers which not their pollinia removed, the greater 32 6 12 number were young flowers under the : buds 2 - Orchis maculata. ‘One plant. Suriey i 21 5 7 Orchis maculata. Two plants. + an 8. Kent . | 28 ae Orchis latifolia. ” Nine plants from 8. Kent, seut me by the Rev. B. 8. Maiden. 50 27 119 The flowers were all mature ; | Orchis fusea. Two plants. S&. El} 8 5 54 Flowers quite mature, and even withered Aceras sutmepoplionn. Four ene s, 63 6 34 Kent . 3 34 OPHRE.E, Cuar. I. In the second lot of O. morio, in the preceding list, we see the injurious effects of the extraordinary cold and wet season of 1860 on the visits of insects, and, consequently, on the fertilisation of this Orchid, very few seed-capsules having been produced. I have examined spikes of O. pyramidalis in which every single expanded flower had its pollinia removed. ‘The forty-nine lower flowers of a spike from Folkestone (sent me by Sir Charles Lyell) actually produced forty- eight fine seed-capsules; and of the sixty-nine lower flowers in three other spikes, seven alone had failed to produce capsules. These facts show how well moths and butterflies perform their office of marriage-priests.* The third lot of O. pyramidalis in the above list grew on a steep grassy bank, overhanging the sea near Torquay, and where there were no bushes or other shelter for Lepidoptera; being surprised how few pol- linia had been removed, though the spikes were old and very many of the lower flowers withered, I gathered, for comparison, six other spikes from two bushy and sheltered valleys, half a mile on each side of the exposed bank; these spikes were certainly younger, and would probably have had several more of their pollinia removed ; but in their present condition we see how much more frequently they had been visited by moths, and consequently fertilised, than those growing on the much exposed bank. The Bee Ophrys and O. pyramidalis grow mingled together in many parts of England ; and they did so here, but the Bee Ophrys, instead of being, as usual, the rarer species, was here * In the summer of 1875, which was a very wet one, I gathered six unusually fine spikes of O, pyra- midalis. ‘These bore 302 flowers, excluding fourteen which were still fully expanded and capable of be- ing fertilised ; and on this occasion only 119 flowers produced cap- sules, 183 having failed to do go. Six spikes of O. maculata bore 187 flowers, of which eighty-two pro- duced capsules, 105 having failed. Cuar. I. FERTILISED BY INSECTS. 35 much more abundant than 0. pyramidalis. No one would readily have suspected that one chief reason of this difference probably was, that the exposed situation was unfavourable to Lepidoptera, and therefore to the seeding of O. pyramidalis ; whereas, as we shall here- after see, the Bee Ophrys is independent of insects. Many spikes of O. latifolia were examined, because, being familiar with the usual state of the closely-allied O. maculata, I_ was surprised to find in nine nearly withered spikes (as may be seen in the list) how few pollinia had been removed. In one instance, however, O. maculata bad been even worse fertilised; for seven spikes with 315 flowers, produced only forty-nine seed- capsules—that is, on an average only seven capsules on each spike. In this case the plants formed larger beds than I had ever before seen ; and I imagine that there were too many flowers for the insects to visit and fertilise all of them. On some other plants of O. maculata growing at no great distance, above thirty capsules had been produced by each spike. Orchis fusca offers a still more curious case of imperfect fertilisation. I examined ten fine spikes from two localities in South Kent, sent to me by Mr. Oxenden and Mr. Malden: most of the flowers on these spikes were partly withered, with the pollen mouldy even in the uppermost flowers; we may therefore infer that no more pollinia would have been removed. I examined all the flowers only in two spikes, on account of the trouble from their withered condition, and the result may be seen in the list, namely, fifty-four flowers with both pollinia in place, and only eight with one or both removed. In this Orchid, and in O. latifolia, neither of which had been sufficiently visited by insects, there were more flowers with one pollinium than with both removed. J casually examined many 36 OPHREZ. Cuar. 1 flowers in the other spikes of O. fusca, and the propor- tion of pollinia removed was evidently not greater than in the two in the list. The ten spikes bore altogether 358 flowers, and, in accordance with the few pollinia removed, only eleven capsules had been formed: five of the ten spikes produced not a single capsule; two spikes had only one, and one had as many as four capsules. As corroborating what I have before said with respect to pollen being often found on the stigmas of flowers which retain their own pollinia, I may add that, of the eleven flowers which had produced capsules, five had both pollinia still within their now withered anther-cells. From these facts the suspicion naturally arises that O. fusca is so rare a species in Britain from not being sufficiently attractive to insects, and to its not producing a sufficiency of seed. CO. K. Sprengel* noticed, that in Germany O. militaris (ranked by Bentham as the same species with 0. fusca) is likewise imperfectly fertilised, but more perfectly than our O. fusca ; for he found five old spikes bearing 138 flowers which had set thirty-one capsules; and he contrasts the state of these flowers with those of Gymnadenia conop- sea, in which almost every flower produces a capsule. An allied and curious subject remains to be discussed. The existence of a well-developed spur-like nectary seems to imply the secretion of nectar. But Sprengel, a most careful observer, thoroughly searched many flowers of O, latifolia and morio, and could never find a drop of nectar; nor could Krinitzt find nectar * ‘Das entdeckte Gcheimniss, tung der Nektarien,’ 1833, s. 28. ete. 8, 404. See also ‘Das entdeckte Geheim- t+ Quoted by J. G. Kurr in his _ niss,’ s. 403. ‘Untersuchungen tiber die bedcu- Cuar, T. SECRETION OF NECTAR. 37 either in the nectary or on the labellum of O. morio, fusca, militaris, maculata or latifolia. I have looked to all our common British species and could find no trace of nectar; I examined, for instance, eleven flowers of O. maculata, taken from different plants growing in different districts, and taken from the most favourable position on each spike, and could not find under the microscope the smallest bead of nectar. Sprengel calls these flowers “Scheinsaftblumen,” or sham-nectar-producers ;—he believes that these plants exist by an organized system of deception, for he well knew that the visits of insects were indispensable for their fertilisation. But when we reflect on the incalcul- able number of plants which have lived during a great length of time, all requiring that insects should carry the pollen-masses from flower to flower in each gene- ration; and as we further know from the number of the pollen-masses attached to their proboscides, that the same insects visit a large number of flowers, we can hardly believe in so gigantic an imposture. He who believes in Sprengel’s doctrine must rank the sense or instinctive knowledge of many kinds of insects, even bees, very low. in the scale. To test the intellect of moths and butterflies I tried the following little experiment, which ought to have been tried on a larger scale. I removed a few already- opened flowers on a spike of O. pyramidalis, and then cut off about half the length of the nectaries of the six next non-expanded flowers. When all the flowers were nearly withered, I found that thirteen of the fifteen upper flowers with perfect nectaries had their pollinia removed, and two alone had their pollinia still in the anther-cells; of the six flowers with their nectaries cut off, three had their pollinia removed, and three were still in place; and this in- 38 OPHRE XE. Cuar. L dicates that moths do not go to work in a quite sense- less manner.* : Nature may be said to have tried this same experi- ment, but not quite fairly; for Orehis pyramidalis, as shown by Mr. Bentham,t often produces monstrous flowers without a nectary, or with a short and imperfect one. Sir C. Lyell sent me several spikes from Folke- stone with many flowers in this condition: I found six without a vestige of a nectary, and their pollinia had not been removed. In about a dozen other flowers, having either short nectaries, or with the labellum imperfect, the guiding ridges being either absent or developed in excess and rendered foliaceous, the pollinia in one alone had been removed, and the ova- rium of another flower was swelling. Yet I found that the saddle-formed discs in these eighteen flowers were perfect, and that they readily clasped a needle when inserted in the proper place. Moths had removed the pollinia, and had thoroughly fertilised the perfect flowers on the same spikes; so that they must have neglected the monstrous flowers, or, if visiting them, the derangement in the complex mechanism of the parts had hindered the removement of the pollinia, and prevented their fertilisation. Notwithstanding these several facts I still suspected that nectar must be secreted by our common Orchids, * Kurr (‘Bedeutung der Nek- tarien,’ 1833, p. 123) cut off the nectaries of fiftcen flowers of Gymnadenia conopsea, and they did not produce a single capsule: he also trcated in the same man- ner fifteen flowers of Platanthera or Habenaria bifolia, and these set only five capsules; but then it should be observed that the nec- taries of both these orchids con- tain free nectar. He also cut off the corolla, leaving the nectary, of forty flowers of Orchis morio, and these set no capsules; and this case shows that insects are guided to the flowers by the corolla. Sixteen flowers of Platanthera treated in the same manner bore only one capsule. Similar experi- ments made by him on Gymna- denia seem to me open to doubt. + ‘Handbook of the British Flora,’ 1858, p. 591. Onar. 1 SECRETION OF NECTAR. 39 and I determined to examine O. morio rigorously. As soon as many flowers were open, I began to examine them for twenty-three consecutive days: I looked at them after hot sunshine, after rain, and at all hours: I kept the spikes in water, and examined them at midnight, and early the next morning: I irritated the nectaries with a bristle, and exposed them to irritating vapours: I took flowers which had lately had their pollinia removed by insects, of which fact I had independent proof on one occasion by finding grains of some foreign pollen within the nectary ; and 1 took other flowers, which judging from their position on the spike, would soon have had their pollinia removed ; but the nectary was invariably quite dry. After the publication of the first edition of this work, I one day saw various kinds of bees visiting repeatedly the flowers of this same Orchid, so that this was evidently the proper time to examine their nectaries ; but I failed to detect under the microscope even the minutest drop of nectar. So it was with the nectaries of O. maculata at a time when I repeatedly saw flies of the genus Empis keeping their proboscides inserted into them for a considerable length of time. Orchis pyramidalis was examined with equal care with the same result, for the glittering points within the nectary were abso- lutely dry. We may therefore safely conclude that the nectaries of the above-named Orchids neither in this country nor in Germany ever contain nectar. Whilst examining the nectaries of O. morio and maculata, and especially of O. pyramidalis and hircina, I was surprised at the degree to which the inner and outer membranes forming the tube or spur were sepa- rated from each other,—also at the delicate nature of the inner membrane, which could be penetrated very easily,—and, lastly, at the quantity of fiuid contained 40 OPUREZ. Cnar, L between the two membranes. So copious is this fluid, that, after cutting off the extremities of the nectaries of O. pyramidalis, and gently squeezing them on glass under the microscope, such large drops of fluid exuded from the cut ends, that I concluded that at last I had found nevtaries which contained nectar; but when I care- fully made, without any pressure, a slit along the upper surface of other nectaries from the same plants, and looked into them, their inner surfaces were quite dry. I then examined the nectaries of Gymnadenia conopsea (a plant ranked by some botanists as a true Orchis) and of Habenaria bifolia, which are always full of necta1 up to one-third or two-thirds of their length. The inner membrane presented the same structure and was covered with papille as in the foregoing species ; but there was a plain difference in the inner and outer membranes being closely united, instead of being in some degree separated from each other and charged with fluid. I was therefore led to conclude that insects penetrate the lax inner membrane of the nectaries of the above-named Orchids, and suck the copious fluid between the two membranes. This was a bold hypo- thesis; for at the time no case was known of insects penetrating with their delicate proboscides even the laxest membrane. But I have now heard from Mr. Trimen, that at the Cape of Good Hope moths and butterflies do much injury to peaches and plums by puncturing their unbroken skins. In Queensland Australia, a moth, the Ophideres fullonica, bores through the thick rind of the orange with its wonder- ful proboscis, provided with formidable teeth.* There is therefore not the least difficulty in believing that Lepidoptera with their delicate proboscides, and bees * My son Francis has described ‘Q. Journal of Microscopical and figured this organ in the Science, vol. xv. 1875, p. 385. Cuap. 1. SECRETION OF NECTAR. 41 with their much stronger ones, could penetrate with ease the soft inner membrane of the nectaries of the above- named Orchids. Dr. H. Miller is also convinced* that insects puncture the thickened bases of the standard petals of the Laburnum,f and perhaps tha petals of some other flowers, so as to obtain the included fluid. The various kinds of bees which I saw visiting the flowers of Orchis morio remained for some time with their proboscides inserted into the dry nectaries, and I distinctly saw this organ in constant movement. I observed the same fact with Empis in the case of 0. maculata ; and on afterwards opening several of the nectaries, I occasionally detected minute brown specks, due as I believe to the punctures made some time before by these flies. Dr. H. Miller, who kas often watched bees at work on several species of O.chis, the nectaries of which do not contain any free nectar, fully accepts my view.{ On the other hand, Delpino still maintains that Sprengel is right, and that insects are continually deceived by the presence of a nectary, though this contains no nectar.§ His belief is founded chiefly on a statement by Sprengel that insects soon find out that it is of no use to visit the nectaries of these orchids, as shown by their fertilising only the * ‘Die Befruchtung,’ &e. p. 235. ¢ Treviranus confirms (‘ Kot. Zeitung,’ 1863, p. 10) a statement made by Salisbury, that when the filaments in the flowers of another leyuminous plant, Edwardsia, fall off, or when they are cautiously separated, a large quantity of sweet tluid flows from the points of separation; and as beforehand there was no trace of any such Huid, it must have been contained, as Treviranus remarks, within the cellular tissue. I may add an ap- parently similar, but really dis- tinct case, namely, the presence of nectar in several monocotyle- donous plants (as described by Ad. Brongniart in ‘ Bull. Soe. Bot. de France,’ tom, i. 1854, p. 75) between the two walls (feuillets) which form the divisions of the ovarium. But the nectar in this case is conducted to the outside by a channel; and the secreting surface is homologivally an ex- terior surface, t ‘Die Befruchtung,’ &c. p. 84. § ‘Ult. Osservazioni sulla Di- cogamia,’ 1875, p. 121. 42 OPHRLA. Cuap. L lower and first opened flowers. But this statement is completely contradicted by my observations previously given, from which it follows that very many of the upper flowers are fertilised; for instance, on a spike of O. pyramidalis with between fifty and sixty flowers, no less than forty-eight had their pollinia removed. Nevertheless, as soon as I learnt that Delpino still be- lieved in Sprengel’s view, I selected during the un- favourable season of 1875 six old spikes of O. maculata, and divided each into halves, so as to observe whether many more capsules were produced by the lower than by the upper half. This certainly was not always the case; for in some of the spikes no difference could be detected between them; in others there were more cap- sules in the lower, while in others there were more in the upper half. A spike of O. pyramidalis examined in the same manner produced twice as many capsules in the upper as in the lower half. Bearing in mind these facts and others before given, it appears to me incredible that the same insect should go on visiting flower after flower of these Orchids, although it never obtains any nectar. Insects, or at least bees, are by no means destitute of intelligence. They recognise from a distance the flowers of the same species, and keep to them as long as they can. When humble- bees have bitten holes through the corolla, as they often do, so as to reach the nectar more easily, hive- bees immediately perceive what has been done and take advantage of the perforations. When flowers having more than a single nectary are visited by many bees, so that the nectar is exhausted in most of them, the bees which afterwards visit such flowers insert their proboscides only into one of the nectaries, and if they find this exhausted, they instantly pass on te another flower. Can it be believed that bees which Cuap. I. SECRETION OF NECTAR. 43 show this much intelligence, should persevere in visiting flower after flower of the above-named Orchids, and in keeping their proboscides in constant movement for some time within the nectaries, in the hope of obtaining nectar which is never present? This, as I have said, seems to me utterly incredible. It has been shown how numerous and beautiful are the contrivances for the fertilisation of Orchids. We know that it is of the highest importance that the pollinia, when attached to the head or proboscis of an insect, should be fixed symmetrically, so as not to fall either sideways or backwards. We know that in the species as yet described the viscid matter of the disc sets hard in a few minutes when exposed to the air, so that it would be a great advantage to the plant if insects were delayed in sucking the nectar, time being thus allowed for the disc to become immovably affixed. It is manifest that insects must be delayed by having to bore through several points of the inner membrane of the nectary, and to suck the nectar from the inter- cellular spaces; and we can thus understand why the nectaries of the above-named species of Orchis do not contain free nectar, but secrete it internally between the two membranes. The following singular relation supports this view in a striking manner. I have found free nectar within the nectaries of only five British species of Ophree, namely, in Gymnadenia conopsea and albida, in Habenaria bifolia and chlorantha, and in Peristylus (or Habenaria) viridis. The first four of these species have the viscid surfaces of the discs of their pollinia naked or not enclosed within pouches, and the viscid matter does not rapidly set hard when exposed to the air, as if it did, it would immediately have been rendered use- less; and this shows that it must differ in chemical 44 OPHREZ. Cuar. I nature from that in the foregoing species of Orchis. But to make sure of this fact I removed the pollinia from their anther-cells, so that the upper as well as the under surfaces of the viscid discs were freely exposed to the air; in Gymnadenia conopsea the disc remained sticky for two hours, and in Habenaria chlorantha for more than twenty-four hours. In Peristylus viridis the viscid disc is covered by a pouch-formed membrane, but this is so minute that botanists have overlooked it. I did not, when examining this species, see the importance of ascertaining exactly how soon the viscid matter set hard; but I copy from my notes the words written at the time: “disc remains sticky for some time when removed from its little pouch.” Now the meaning of these facts is clear: as the viscid matter of the discs of these five latter species is so adhesive that it serves to attach the pollinia firmly to the insects which visit the flowers, without setting hard, there would be no use in the insects being delayed by having to bore holes at several points through the inner membrane of the nectaries; and in these five species, and in these alone, we find copious nectar ready stored for rapid suction in open nectaries, On the other hand, whenever the viscid matter sets hard by exposure for a short time to the air, it would manifestly be advantageous to the plant, if insects were delayed in obtaining the nectar; and in all such species the nectar is lodged within intercellular spaces, so that it can be obtained only by the inner mem- brane being penetrated at several points, and this will require time. If this double relation is accidental, it is a fortunate accident for the plants; but I cannot believe it to be so, and it appears to me one of the most wonderful cases of adaptation which has ever been recorded. Cuap, II OPHRYS MUSCIFERA. 45 CHAPTER II. OPHREE—continued. Fly and Spider Ophrys—Bee Ophrys, apparently adapted for perpetuat _ self-fertilisation, but with paradoxical contrivances for intercrossing —Herminium monorchis, attachment of the pollinia to the front legs of insects—Peristylus viridis, fertilisation indirectly effected by nectar secreted from three parts of the labellum—Gymnadenia conopsea, and other species Habenaria or Platanthera chlorantha and bifolia, their pollinia attached to the eyes of Lepidoptera—Other species of Habenaria—Bonatea—Disa—Summary on the powers of movement in the pollinia. Tue genus Ophrys differs from Orchis chiefly in having separate pouch-formed rostella,* instead of the two being confluent. In Ophrys muscifera, or the Fly Ophrys, the chief peculiarity is’ that the caudicle of the pollinium (B, fig. 5) is doubly bent. The nearly circular piece of membrane, to the under side of which the ball of viscid matter adheres, is of considerable size, and forms the summit of the rostellum. It is thus freely exposed * It is not correct to speak of two rostella, but the inaccuracy may be forgiven from its conve- nience. The rostellum strictly is a single organ, formed by the moditication of the dorsal stigma and pistil; so that in Ophrys the two pouches, the two viscid discs, and the space between them to- gether form the true rostellum. Again, in Orchis I have spoken of the pouch-formed organ as the rostellum, but strictly the rostel- am includes the little crest or fold of membrane (see B in fig. 1) projecting between the bases of the anther-cells, This folded crest (sometimes converted into a solid ridge) corresponds with the smooth surface lying between the two pouches in Ophrys, and owes its protuberant and folded condi- tion in Orchis to the two pouches having been brought together and rendered confluent. This modi- fication will be more fully ex- plained in a future chapter. 46 OPHRES. Cuar. I to the air, instead of lying almost hidden at the base of the anther, as in Orchis, and thus kept damp. Never: theless, when a pollinium is removed, the caudicle bends downwards in the course of about six minutes, and, therefore, at an unusually slow rate; the upper Fig. 5. OPHRYS MUSCIFERA, OR FLY OPuHRYS, ad, anther. s. stigma. of the bases of the anther-cells 5. r,r. rostella, 7, labellum. but this is not shown from the A. Flower viewed in front: the two foreshortening of the drawing. upper petals are almost cylin- | B. One of the two pollinia removed drical and hairy; the two ros- from its anther-cell, and viewed tella stand a little in advance laterally. end still remaining curved. I formerly thought that it was incapable of any movement, but have been con- vinced by Mr. T. H. Farrer of my error. The ball of viscid matter is bathed in fluid within the pouch formed by the lower half of the rostellum, and this is necessary, Cuap. IT. OPHRYS MUSCIFERA. 47 as the viscid matter quickly sets hard when exposed to the air. The pouch is not elastic, and does not spring up when the pollinium is removed. Such elasticity would have been useless, as there is here a separate pouch for each viscid disc; whereas in Orchis, after ‘one pollinium has been removed, the other has to be kept covered up and ready for action. Hence it appears that nature had been so economical as to save even superfluous elasticity. The pollinia cannot, as I have often proved, be shaken out of the anther-cells. That insects of some kind visit the flowers, though not frequently, and remove the pollinia, is certain, as we shall immediately see. Twice I have found abundant pollen on the stigmas of flowers, in which both pollinia were still in their cells ; and no doubt this might have been much oftener ob- served. The elongated labellum affords a good landing- place for insects: at its base, just beneath the stigma, there is a rather deep depression, representing the nectary in Orchis; but I could never see a trace of nectar within it; nor have I ever observed any insects approach these inconspicuous and scentless flowers, often as | have watched them. There is, however, on each side of the base of the labellum a small shining projection, having an almost metallic lustre, which appears curi- ously like a drop of fluid or nectar ; and as these flowers are only visited occasionally by insects, Sprengel’s view of the existence of sham-nectaries is far more probable in this case than in any other known to me. On several occasions I have detected minute punctures in these protuberances, but I was not able to decide whether they had been made by insects, or whether superficial cells had spontaneously burst. Similar shining pro- tuberances are present on the labella of all the other species of Ophrys. The two rostella stand not far 18 OPHREZ. Cuar. IL, apart, and project over the stigma; and if any object is gently pushed against one of them, the pouch is depressed and the viscid ball together with the pol- linium adheres to it and is easily removed. The structure of the flower leads me to believe that small insects (as we shall see in the case of Listera) crawl up the labellum to its base, and that in bending their heads downwards, so as to puncture and suck, or only to examine one of the small shining protuberances, they push against the pouch, and a pollinium is attached to their heads; they then fly to another flower, and there bending down in a similar manner, the attached and doubly-bent pollinium, after the movement of depression, strikes the sticky stigmatic surface, and leaves pollen on it. Under the next species we shall see reason for believing that the natural double cur- vature of the caudicle compensates for its slight power of movement, compared with that in all the species of Orchis. Number of Flowers. Both Pollinia 7 Both Poll* or one removed lin thelr Cells In 1858, 17 plants, bearing 57 flowers, 30 97 growing near each other were examined In 1858, 25 plants growing in another 15 50 spot, and bearing 65 flowers . . In 1860, 17 plants, bearing 61 flowers. 28 33 In 1861, 4 plants from 8. Kent, bearing 24 flowers (all the previous plants having 15 9 grown in N. Kent) é . g Tutal » 2 « ss | sig That insects visit the flowers of the Fly Ophrys and remove the pollinia, though not effectually or suffi- Cuap. II. JPHRYS MUSCIFERA.' 49 ciently, the following cases show. During several years before 1858 I occasionally examined some flowers, and found that only thirteen out of 102 had one or both pollinia removed. Although at the time I re- corded in my notes that most of the flowers were partly withered, I now think that I must have included many young flowers, which might perhaps have been subsequently visited ; so I prefer trusting to the fol- lowing observations. We here see that, out of 207 flowers examined, not half had been visited by insects. Of the eighty-eight flowers visited, thirty-one had only one pollinium re- moved. As the visits of insects are indispensable for the fertilisation of this Orchid, it is surprising (as ix the case of Orchis fusca) that the flowers have not been rendered more attractive to insects. The number of seed-capsules produced is proportionably even less than the number of flowers visited by insects. The year 1861 was extraordinarily favourable to this species in this part of Kent, and I never saw such numbers in flower; accordingly I marked eleven plants, which bore forty-nine flowers, but these produced only seven capsules. Two of the plants each bore two capsules, and three other plants each bore one, so that no less than six plants did not produce a single capsule! What are we to conclude from these facts? Are the conditions of life unfavourable to this species, though during the year just alluded to it was so numerous in some places as to deserve to be called quite common? Could the plant nourish more seed ; and would it be of any advantage to it to produce more seed? Why does it produce so many flowers, if it already produces a sufficiency of seeds? Something seems to be out of order in its mechanism or in its conditions. We shall presently see that Ophrys apifera or the Bee Ophrys 50 OPHREZ. Cuapr. IL presents a wonderful contrast in every flower producing a capsule. Ophrys aranifera, or the Spider Ophrys.—I am in- debted to Mr. Oxenden for some spikes of this rare Fig. 6. species. Whilst the pollinia . remain enclosed within their cells, the lower part of the cau- dicle projects up in a straight line from the viscid disc, and therefore has a very different form from the corresponding Ophrys avanifera. part of the caudicle of 0. mus- A. Pollinium before the act of cifera ; but the upper part ( A, depression. . : B. Pollinium after the act of fig. 6) is a little bent forward, depression. that is, towards the labellum. The point of attachment of the caudicle to the disc is hidden within the bases of the anther-cells, and is thus kept damp; consequently, as soon as the pollinia are exposed to the air, the usual movement of depression takes place, and they sweep through an angle of about ninety degrees. By this movement they assume, supposing them to be attached to an insect’s head, a position exactly adapted for striking the stigmatic surface, which is situated, relatively to the potch-formed rostella, rather lower down in the flower than in the Fly Ophrys. I examined fourteen flowers of the Spider Ophrys, several of which were partly withered; and in none were both pollinia, and in three alone was one pollinium removed. Hence this species, like the Fly Ophrys, is but little visited by insects in England. In parts of Italy it is even less visited, for Delpino states* that in Liguria hardly one flower out of 3000 sets a * + Ult. Osserv. s. Dicogamia, &c. Parte i. 1868-69, p. 177. Cuar. IT. OPHRYS ARACIINITES, ol capsule, though near Florence rather more capsules are produced. The labellum does not secrete any nectar. The flowers, however, must be occasionally visited and fertilised by insects, for Delpino found* pollen-masses on the stigmas of some flowers which still retained both their own pollinia. The anther-cells are remarkably open, so that with some plants which were sent me in a box, two pair of pollinia fell out, and stuck by their viscid discs to the petals. Here we have an instance of the first appearance of a trifling structure which is of not the least use to its possessor, but becomes when a little more developed, highly beneficial to a closely-allied species; for although the open state of the anther-cells is useless to the Spider Ophrys, it is of the highest importance, as we shall presently see, to the Bee Ophrys. The flexure of the upper end of the caudicle of the pollinium is of service to the Spider and Fly Ophrys, by aiding the pollen-masses, when carried by insects to another flower, to strike the stigma; but by an increase of this bend together with increased flexi- bility in the Bee Ophrys, the pollinia become adapted for the widely different purpose of self-fertilisation. Ophrys arachnites—This form, of which Mr. Oxenden sent me several living specimens, is considered by some botanists as only a variety of the Bee Ophrys, by others as a distinct species. The anther-cells do not stand so high above the stigma, and do not overhang it so much, as in the Bee Ophrys, and the pollen masses are more _pollinium of elongated. The caudicle is only two- phrysar achnite thirds, or even only half as long as that of the Bee Fig. 7. * ‘Fecondazione nelle Piante Antocarpee,’ 1867, p. 20. 52 OPHREZ. Cuap. IL Ophrys, and is much more rigid; the upper part is naturally curved forward; the lower part undergoes the usual movement of depression, when the pollinia are removed from their cells. The pollen-masses never fall spontaneously out of their cells. This plant, therefore, differs in every important respect from 0. apifera, and seems to be much more closely allied to O. aranifera. Ophrys scolopax of Cavanilles.—This form inhabits the north of Italy and the south of France. Mr. Mogegridge says* that at Mentone it never shows any tendency to fertilise itself, whilst at Cannes the pollen- masses naturally fall out of their cells and strike the stigma. He adds: “This material difference between the two is accomplished by a very slight bend in the anther-cells, which are prolonged into a beak of variable length, in the case of the self-fertilising blossoms.” Ophrys apifera—The Bee Ophrys differs widely from the great majority of Orchids in being excellently constructed for fertilising itself. The two pouch-formed rostella, the viscid discs, and the position of the stigma, are nearly the same as in tue other species of Ophrys ; but the distance of the two pouches from each other, and the shape of the pollen-masses are somewhat variable.t The caudicles of the pollinia are remark- ably long, thin, and flexible, instead of being, as in all the other Ophres seen by me, rigid enough to stand upright. They are necessarily curved forward at their upper ends, owing to the shape of the anther-cells; and the pear-shaped pollen-masses lie embedded high above and directly over the * ‘Journ. Liun. Soe.’ vol. viii. symmetrically confluent as in the 1865, p. 258. genus Orchis, and with the two + I once found a single flower viscid discs likewise confluent, as on the summit of a spike, with in Orchis pyramidalis or hircina, the two rostella as completely and Ouap. II. OPHRYS APIFERA. 53 stigma. The anther-cells naturally open soon after the flower is fully expanded, and the thick ends of the pollen-masses then fall out, the viscid discs still remaining in their pouches. Slight as is the weight of the pollen-masses, yet the caudicles are so thin and quickly become so flexible, that in the course of a few hours they sink down, until they hang freely in the air Fig. 8. GPURYS APIFERA, OR BEE OPURYS. a. anther. out of tHe anther-cell; and » 2 labellum. the other has fallen almost to A. Side view of flower, with the its full extent, opposite to the upper sepal and the two upper hidden stigmatic surface. petals removed. One pollinium, | B. Pollinium in the position in with its dise still in its pouch, which it lies embedded. is represented as jast falling (see lower pollen-mass in fig. A) exactly opposite to and in front of the stigmatic surface. In this position a breath of air, acting on the expanded petals, sets the flexible and elastic caudicles vibrating, and they almost immediately strike the viscid stigma, and, being there secured, impregnation is effected. ‘lo make sure that no other aid was requisite, thorgh 54 OPHREZ, Caap. IL. the experiment was superfluous, I covered up a plant under a net, so that the wind, but no insects, could pass in, and in a few days the pollinia became attached to the stigmas. But the pollinia of a spike kept in water in a still room remained free, suspended in front of the stigma, until the flowers withered. Robert Brown first observed that the structure of the Bee Ophrys is adapted for self-fertilisation.* When we consider the unusual and perfectly-adapted length, as well as the remarkable flexibility of the caudicles ; when we see that the anther-cells naturally open, and that the masses of pollen, from their weight, slowly fall down to the exact level of the stigmatic surface, and are there made to vibrate by the slightest breath of wind until the stigma is struck; it is impossible to doubt that these several points of structure and function, which occur in no other British Orchid, are ' specially adapted for self-fertilisation. The result is what might have been anticipated. 1 have often noticed that the spikes of the Bee Ophrys apparently ‘produced as many seed-capsules as flowers ; and near Torquay I carefully examined many dozen plants, some time after the flowering season; and on all I-found from one to four, and occasionally five, fine capsules, that is, as many capsules as there had been flowers. In extremely few cases, with the excep- tion of a few deformities, generally on the summit of the spike, could a flower be found which had not pro- duced a capsule. Let it be observed what a contrast this species presents with the Fly Ophrys, whicb requires insect aid for its fertilisation, and which from forty-nine flowers produced only seven capsules ! * © Transact. Linn. Soc.” vol. common to the genus. As far aa xvi. p. 740. Brown erroneously the four British species are con- believed that this peculiarity was cerned, it applics tu this one alone. Cuap. IL OPHRYS APIFERA. 55 From what I had then seen of other Orchids, J was so much surprised at the self-fertilisation of this species, that I examined during many years, and asked others to examine, the state of the pollen-masses in many hundreds of flowers, collected in various parts of England. The particulars are not worth detailing ; but I may give as an instance, that Mr. Farrer found in Surrey that not one flower out of 106 had lost both pollinia, and that only three had lost a single one. In the Isle of- Wight, Mr. More examined 136 flowers, and of these the very unusual number of ten had lost both, and fourteen had lost one; but then he found that in eleven cases the caudicles had been gnawed through apparently by snails, the discs still remaining in their pouches; so that the pollinia had not been carried away by insects. In some few cases, also, in which I found the pollinia removed, the petals were marked with the slime of snails. Nor must we forget that a blow from a passing animal, and possibly heavy storms of wind might occasionally cause the loss of one or both pollinia. During most years the pollen-masses of the many hundred flowers which were examined, adhered with the rarest exceptions to the stigma, with their discs still enclosed within the pouches. But in the year 1868, from some cause the nature of which I cannot conjecture, out of 116 flowers gathered in two localities in Kent, seventy-five retained both pollinia in their cells; ten had one pollinium, and only thirty-one had both adhering to the stigma. Long and often as I have watched plants of the Bee Ophrys, I have never seen one visited by any insect.* Robert Brown imagined * Mr. Gerard E. Smith, in his ‘Catalogue of Plants of S. Kent, 56 OPHREZ. Osap. IT. that the flowers resembled bees in order to deter their visits, but this seems extremely improbable. The flowers with their pink sepals do not resemble any British bee, and it is probably true, as I have heard it said, that the plant received its name merely from the — hairy labellum being somewhat like the abdomen of a humble-bee. We see how fanciful many of the names are,—one species being called the Lizard and another the Frog Orchis. The resemblance of O. muscifera to a fly is very much closer than that of O. apifera toa bee; and yet the fertilisation of the former absolutely depends on and is effected by the means of insects. All the foregoing observations relate to England, but Mr. Moggridge made similar ones on the Bee Ophrys in Northern Italy and Southern France, as did Treviranus* in Germany, and Dr. Hooker in Morocco. We may therefore conclude,—from the pollinia spon- taneously falling on the stigma—from the co-related structure of all the parts for this purpose—and from almost all the flowers producing seed-capsules—that this plant has been specially adapted for self-fertilisa- tion. But there is another side to the case. When an object is pushed against one of the pouches of the rostellum, the lip is depressed, and the large viscid disc adheres firmly to it; and when the object is removed, so is the pollinium, but perhaps not quite so readily as in the other species of Ophrys. Even after the pollen-masses have naturally fallen out of their cells on to the stigma, their removal can sometimes be thus effected. Assoon as the disc-is 1829, p. 25, says: “Mr. Price cannot conjecture. has frequently witnessed attacks * ‘Bot. Zeitung, 1863, p. 241. made upon the Bee Orchis by a This botanist at first doubted my bee, similar to those of the observations on Ophrys apifera troublesome Apis muscorum.” and aranifera, but has since fully What this sentence means I confirmed them. Cuap. I. OPHRYS APIFERA. 57 drawn out of its pouch a movement of depression commences, by which the pollinium if attached to the front of an insect’s head would be brought into a proper position for striking the stigma. When a pollen-mass is placed on the stigma and then with- ‘drawn, the elastic threads by which the packets are tied together break, and leave several packets on the viscid surface. In all other Orchids the meaning of these several contrivances is unmistakably clear— namely, the downward movement of the lip of the ros- tellum when gently pushed—the viscidity of the disc —the depression of the caudicle as soon as the disc is exposed to the air—the rupturing of the elastic threads—and the conspicuousness of the flower. Are we to believe that these adaptations for cross-fertilisa- tion in the Bee Ophrys are absolutely purposeless, as would certainly be the case if this species has always been and will always be self-fertilised ? It is, however, just possible that insects, although they have never been seen to visit the flowers, may at rare intervals transport the pollinia from plant to plant, during such seasons as that of 1868, when the pollinia did not all fall out of the anther-cells so as to reach the stigmas. The whole case is perplexing in an unparalleled degree, for we have in the same flower elaborate contrivances for directly opposed objects. That cross-fertilisation is beneficial to most Orchids, we may infer from the innumerable structures serving for this purpose which they present; and I have elsewhere shown in the case of many other groups of plants* that the benefits thus derived are of high importance. On the other hand, self-fertilisation is manifestly advantageous in as far as it ensures a full * ‘The Effects of Cross and Self-Fertilisntion in the Vegetable Kingdom,’ 1876. 58 OPHREZ. Cua, IL supply of seed; and we have seen with the other British species of Opnrys which cannot fertilise them- selves, how small a proportion of their flowers produce capsules. Judging therefore from the structure of the flowers of O. apifera, it seems almost certain that at some former period they were adapted for cross- fertilisation, but that failing to produce a sufficiency of seed they became slightly modified so as to fertilise themselves. It is, however, remarkable on this view, that none of the parts in question show any tendency to abortion—that in the several and distant countries which the plant inhabits, the flowers are still con- spicuous, the discs still viscid, and the caudicles still retain the power of movement when the discs are ex- posed to the air. The metallic points at the base of the labellum are however smaller than in the other ‘species; and if these serve to attract insects, this dif- ference is of some signification. As it can hardly be doubted that O. apifera was at first constructed so as to be regularly cross-fertilised, it may be asked will it ever revert to its former state; and if it does not so revert, will it become extinct? These questions cannot be answered, any more than in the case of those plants which are now propagated exclusively by buds, stolons, &c., but which produce flowers that rarely or never set any seed; and there is reason to believe that a sexual propagation is closely analogous to long-continued self-fertilisation. Finally Mr. Moggridge has shown that in North Italy Ophrys apifera, aranifera, arachnites, and scolopax are connected by so many and such close intermediate links,* that all seem to form a single species in * These forms are illustrated by ‘ Verhandlungen der Kaiser, beautiful coloured drawings in Leop. Car. Akad.’ (Nov. Act.), the ‘Flora of Mentone, pi.43 to tom. xxxv. 1869 45; and in his memoir in the Cuar. II. HERMINIUM MONORCHIS. 59 accordance with the belief of Linneus, who grouped them all together under the name of Ophrys insectifera. Mr. Moggridge further shows that in Italy 0. aranifera flowers first, and O. apifera last, the intermediate forms at intermediate periods; and according to Mz. Oxenden, the same fact holds good to a certain extent in Kent. The three forms which inhabit England do not seem to blend into one another as in Italy, and I am assured by Mr. Oxenden, who has closely attended to these plants in their native homes, that 0. aranifera and apifera always grow in distinct spots. The case therefore is an interesting one, as here we have forms which may be and generally have been ranked as true species, but which in North Italy have not as yet been fully differentiated. The case is all the more interest- ing, as the intermediate forms can hardly be due to the crossing of O. aranifera with apifera; this latter species being regularly self-fertilised and apparently never visited by insects. Whether we rank the several forms of Ophrys as closely allied species or as mere varieties of the same species, it is remarkable that they should differ in a character of such physiological importances as the flowers of some being plainly adapted for self-fertilisation, whilst the flowers of others are strictly adapted for cross-fertilisation, being utterly sterile if not visited by insects. Herminium monorchis.—The Musk Orchis, which is a rare British plant, is generally spoken of as having naked glands or discs, but this is not strictly correct. The disc is of unusual size, nearly equalling the mass of pollen-grains : it is subtriangular, with one side pro- tuberant, and somewhat resembles a distorted helmet in shape: it is formed of hard tissue with the base hollowed out, and viscid; the base resting on and being covered by a narrow strip of membrane, which is 60 OPHREZ. Cuar. [1 easily pushed away, and answers to the pouch in Orchis. The whole upper part of the helmet answers to the minute oval bit of membrane to which the caudicle of Orchis is attached and which in Ophrys is larger and convex. When the lower part of the helmet is moved by any pointed object, the point readily slips into its hollow base, and is there held so firmly by the viscid matter, that the whole helmet appears adapted to stick to some prominent part of an insect’s body. The caudicle is short and very elastic ; it is attached not to the apex of the helmet, but to the hinder end; if it had been attached to the apex, the point of attachment would have been freely exposed to the air and not kept damp; and then the pollinium when removed from its cell would not have been %yuickly depressed. This movement is well marked, and serves to bring the end of the pollen-mass into a proper position for striking the stigma, ‘The two viscid discs stand wide apart. There are two transverse stigmatic. surfaces, meeting by their points in the middle; but the broad part of each lies directly beneath each disc. The labellum is remarkable from not differing much in shape from the two upper petals, and from not always occupying the same position in reference to the axis of the plant, owing to the ovarium being more or less twisted. This state of the labellum is intelligible, for as we shall see, it does not serve as a landing-place for insects. It is upturned, and together with the two other petals makes the whole flower in some degree tubular. At its base there is a hollow so deep as almost to deserve to be called a nectary; but I could not perceive any nectar, which, as I believe, remains enclosed in the intercellular spaces. The flowers are very small and inconspicuous, but emit a strong honey- Cuar. II. IIERMINIUM MONORCHIS. 61 like odour. They seem highly attractive to insects; in a spike with only seven flowers recently open, four had both pollinia, and one had asingle pollinium removed. When the first edition of this book appeared I did not know how the flowers were fertilised, but my son George has made out the whole process, which is’ extremely curious and differs from that in any other Orchid known to me. He saw various minute insects entering the flowers, and brought home no less than twenty-seven specimens with pollinia (generally with only one, but sometimes with two) attached to them. These insects consisted of minute Hymenoptera (of which Tetrastichus diaphantus was the commonest), of Diptera and Coleoptera, the latter being Malthodes brevicollis, ‘The one indispensable point appears to be that the insect should be of very small size, the largest being only the =; of an inch in length. The pollinia were always attached to the same place, namely, to the outer surface of the femur of one of the front legs, and generally to the projection formed by the articulation of the femur with the coxa. The . cause of this peculiar mode of attachment is suffici- ently clear: the middle part of the labellum stands so close to the anther and stigma, that insects always enter the flower at one corner, between the edge of the labellum and one of the upper petals; they also almost always crawl in with their backs turned directly or obliquely towards the labellum. My son saw several which began to crawl into the flowers in a different position; but they came out and changed their posi- tion. Standing in either corner of the flower, with their backs turned towards the labellum, they insert their heads and fore legs into the short nectary, which is seated between the two widely separated viscid discs, I ascertained that they had occupied this position by 62 OPURE.E. Cuar. IL. finding three dvad insects, permanently glued to the discs. Whilst sucking the nectar, which takes two or three minutes, the projecting joint of the femur stands under the large helmet-like viscid disc on either side ; and when the insect retreats, the disc exactly fits on and is glued to the prominent joint, or to the surface of the femur. The movement of depression in the caudicle now takes place, and the mass of pollen-grains then projects just beyond the tibia; so that the insect, when entering another flower, can hardly fail to ferti- lise the stigma, which is situated directly beneath the disc on either side. Fig. 9. PrRISTYLUS VIRIDIS, OR FROG OrcuIs, Frout view of flower. a. anther. n'n', lateral nectarics. 8. stigma. t, Jabellum. n. orifice of central nectary. Peristylus viridis.—This plant, which bears the odd name of the Frog Orchis, has been placed by many botanists in the genus Habenaria or Platanthera; but as the discs are not naked, it is doubtful whether this Cuar. IL PERISTYLUS VIRIDIS. 63 classification can be correct. The rostella are small and widely separated from each other. The viscid matter on the under side of the disc forms an oval ball which is enclosed within a small pouch. The upper membrane to which the caudicle is attached is of large size relatively to the whole disc, and is freely exposed to the air. Hence probably it is that the pollinia when removed from their cases do not become depressed until, as Mr. T. H. Farrer has observed, twenty or thirty minutes have elapsed. Owing to this long interval, I formerly thought that they did not undergo any movement of depression. Supposing a pollinium to be attached to the head of an insect, and to have become depressed, it will stand at the proper angle, vertically, for striking the stigma. But from the lateral position of the anther-cells, notwithstanding that they converge a little towards their upper ends, it is difficult at first to see how the pollinia when removed by insects are afterwards placed on the stigma; for this is of small size and is situated in the middle of the flower between the two widely separated rostella. The explanation is, I believe, as follows. The base of the elongated labellum forms a rather deep hollow in front of the stigma, and in this hollow, but some way in advance of the stigma, a minute slit-like orifice (1) leads into a short bilobed nectary. Hence an insect, in order to suck the nectar with which the nectary is filled, would have to bend down its head in front of the stigma. The labellum has a medial ridge, which would probably induce an insect first to alight on either side; but, apparently to make sure of this, besides the true nectary, there are two spots (n'n’) which secrete drops of nectar on each side at the base of the labellum, bordered by prominent edges, directly 64 OPHRE. Cuap. Il beneath the two pouches. Now let us suppose an insect to alight on one side of the labellum so as first to lick up the exposed drop of nectar on this side; from the position of the pouch exactly over the drop, it would almost certainly get the pollinium of this side attached to its head. If it were now to go to the mouth of the true nectary, the pollinium attached to its head from not having as yet become depressed would not touch the stigma; so that there would be no self-fertilisation, The insect would then probably suck the exposed drop of nectar on the other side of the labellum, and would perhaps get another pollinium attached to its head ; it would thus be considerably delayed by having to visit the three nectaries. It would then visit other flowers on the same plant, and afterwards flowers on a distinct plant; and by this time, but not before, the pollinia will have undergone the movement of depression and will be in a proper position for effecting cross-fertilisa- tion. It thus appears that the secretion of nectar at three separate points of the labellum,—the wide dis- tance apart of the two rostella—and the slow down- ward movement of the caudicle without any lateral movement—-are aJl correlated for the same purpose of cross-fertilisation. , To what extent this Orchis is frequented by insects, and what the kinds are, I do not know, but several of the flowers on two spikes, sent me by the Rev. B. 8. Malden, had a single pollintum removed, and one flower had both removed. We now come to two genera, namely, Gymnadenia and Habenaria or Platanthera, including four British species, which have uncovered viscid discs. The viscid matter, as before remarked, is of a somewhat different nature from that in Orchis, Ophrys, &c., and does not Cuav, II. GYMNADENIA CONOPSEA. 65 rapidly set hard. Their nectaries are stored with free nectar. With respect to the uncovered condition of the dises, the last species, or Peristylus viridis, is in an almost intermediate condition. The four following species compose a much broken series. In Gymna- denia conopsea the vicid discs are narrow and much elongated, and lie close together; in G. albida they are less elongated, but still approximate ; in Habenaria bifolva they are oval and far apart; and, lastly, in H. chlorantha they are circular and much farther apart. Gymnadenia conopsea.—In general appearance this plant resembles pretty closely a true Orchis. The pollinia differ in having naked, narrow, strap-shaped Fig. 10. GYMNADENIA CONOPSEA, A, Pollinium, before the act of | B, Pollinium, after the act of de- depression. pression, but before it has closely clasped the dise. discs, which are as long as the caudicles (fig. 10). When the pollinia are exposed to the air the caudicle is depressed in from thirty to sixty seconds; and as the posterior surface of the caudicle is slightly hol- lowed out, it closely clasps the upper membranous surface of the disc. The mechanism of this movement will be described in the last chapter. The elastic threads by which the packets of pollen are bound to- gether are unusually weak, as is likewise the case with 66 OPHREE. Cuar. IL tlie two following species of Habenaria: this was well shown by the state of specimens which had been kept in spirits of wine. This weakness apparently stands in relation to the viscid matter of the discs not setting hard and dry as in Orchis; so that a moth with a pollinium attached to its proboscis might be enabled to visit several flowers without having the whole polli- nium dragged off by the first stigma which was struck. The two strap-shaped discs lie close together, a and form the arched roof of the entrance into the nectary. They are not protected, as in Orchis, by a lower lip or pouch, so that the structure of the rostellum is simpler. When we come to treat of the homologies of the ros- tellum we shall see that this difference is due to a small change, namely, to the lower and exterior cells of the rostellum resolving themselves into viscid matter; whereas in Orchis the exterior surface retains its early cellular or membranous condition. As the two viscid discs form the roof of the mouth of the nectary, and are thus brought down near to the labellum, the two stigmas, instead of being confluent and standing beneath the rostellum, as in most of the species of Orchis, are lateral and separate. These stigmas consist of protuberant, almost horn-shaped, processes on each side of the nectary. That their surfaces are really stigmatic I ascertained by finding them deeply penetrated by a multitude of pollen- tubes. As in the case of Orchis pyramidalis, it is a pretty experiment to push a fine’ bristle straight into the narrow mouth of the nectary, and to observe how certainly the narrow elongated viscid discs, forming the roof, stick to the bristle. When the bristle is withdrawn, the pollinia adhering to its upper side are withdrawn; and as the discs form the sides of the arched roof, they adhere somewhat to the sides Cuap. IL. GYMNADENIA CONOPSEA. 67 of the bristle. They then quickly become depressed so as to lie in the same line with the bristle,—one a little on one side, and the other on the other side; and if the bristle, held in the same relative position, be now inserted into the nectary of another flower, the two ends of the pollinia accurately strike the two protu- berant stigmatic surfaces, situated on each side of the mouth of the nectary. The flowers smell sweet, and the abundant nectar always contained in their nectaries seems highly attractive to Lepidoptera, for the pollinia are soon and effectually removed. For instance, in a spike with forty-five open flowers, forty-one had their pollinia removed, or had pollen left on their stigmas: in another spike with fifty-four flowers, thirty-seven had both pollinia, and fifteen had one pollinium, removed ; so that only two flowers in the whole spike had neither pollinium removed. My son George went at night to a bank where this species grows plentifully, and soon caught Plusia chrysitis with six pollinia, P. gamma with three, Anaitis plagiata with five, and Triphena pronuba with seven pollinia attached to their proboscides. I may add that he also caught the first-named moth in my flower-garden, with the pollinia of this Orchis attached to its proboscis, but with all the pollen-grains removed, although the garden is a quarter of a mile distant from any spot where the plant grows. Many of the above moths had only a single pollinium attached, somewhat laterally to their proboscides; and this would happen in every case, unless the moth stood directly in front of the nectary and inserted it proboscis exactly be- tween the two discs. But as the labellum is rather broad and flat, with no guiding ridges like those on the labellum of Orchis pyramidalis, there is nothing to 68 OPHREZ. Cuar. I compel moths to insert their proboscides symmetrically into the nectary, and there would be no advantage in their doing so. Gymnadenia albida.—The structure of the flower of this species resembles in most respects that of the last ; but, owing to the upturning of the labellum, it is rendered almost tubular. The naked elongated discs‘are minute and approximate. The stigmatic sur- faces are partially lateral and divergent. The nectary is short, and full of nectar. Small as the flowers are, they seem highly attractive to insects: of the eighteen lower flowers on one spike, ten had both, and seven had one pollinium removed; on some older spikes all the pollinia had been removed, except from two or three of the uppermost flowers. Gymnadenia odoratissima is an inhabitant of the- Alps, and is said by Dr. H. Miller* to resemble in all the above characters G. conopsea. As the flowers, which are pale coloured and highly perfumed, are not visited by butterflies, he believes that they are fertilised exclusively by moths. The North American G. tri- dentata, described by Professor Asa Gray, differs in an important manner from the foregoing species. The unther opens in the bud, and the pollen-grains, which in the British species are tied together by very weak threads, are here much more incoherent, and some in- variably fall on the two stigmas and on the naked cellular tip of the rostellum; and this latter part, strange to say, is penetrated by the pollen-tubes. The flowers are thus self-fertilised. Nevertheless, as Pro- fessor Gray adds, “all the arrangements for the removal * ‘Nature,’ Dec. 31, 1874, p. note p. 260; and vol. xxxvi. 1863, 469, p. 293. In the latter paper he + ‘American Journal of Science,’ adds some remarks on G. flava and vol. xxxiv. 1862, p. 426, and foot- nivea. Cuap. IL HABENARIA CHLORANTHA. 69 of the pollinia by insects, including the movement of depression, are as perfect as in the species which depend upon insect aid.” Hence there can be little doubt that this species is occasionally cross-fertilised. Fig. 11. HABENARIA CULORANTHA, OR BUTTERFLY Orcilis. aa, anther-cells. B, A pollintum. (This has hardly d. disc of pollinium, a sufficiently elongated appear- 8 stigma. ance.) The drum-like pedicel n. nectary. is hidden behind the disc. n’. orifice of nectary. C. Diagram, giving a__ section 4 Jabellum. through the viscid disc, the A. Flower viewed in front, with all drum-like pedicel, and the the sepals and petals removed attached end of the caudicle, except the labellum with its | - The viscid disc is formed of an nectary, which is turned to one upper membrane with a layer side, of viscid matter beneath. Habenaria or Platanthera chlorantha.—The pollinia of the Large Butterfly Orchis differ considerably from those of any species hitherto mentioned. The two 70 OPHREZ. Cuar. 11 anther-cells are separated from each other by a wide space of connective membrane, and the pollinia are enclosed in a backward sloping position (fig. 11). The viscid discs front each other, and stand in advance of the stigmatic surface. In consequence of their forward position, the caudicles and pollen-masses are much elongated. Tach viscid disc is cireular, and, in the early bud, consists of a mass of cells, of which the exterior layers (answering to the lip or pouch in Orchis) resolve themselves into adhesive matter. This matter has the property of remaining adhesive for at least twenty-four hours after the pollinium has been removed from its cell. The disc, externally covered with a thick layer of adhesive matter (see fig. CO, which stands so that the layer of viscid matter is below) is produced on its opposite and embedded side into a short drum-like pedicel. This pedicel is continuous with the membranous portion of the disc and is formed of the same tissue. The caudicle of the pollinium is attached in a transverse direction to the embedded end of the pedicel, and its extremity is prolonged, asa bent rudimentary tail, just beyond the drum. The caudicle is thus united to the viscid disc in a very different manner, and in a plane at right angles, to what occurs in the other British Orchids. In the short drum- like pedicel, we have a small development of the long pedicel of the rostellum, which is so conspicuous in many Vande, and which connects the viscid dise with the true caudicles of the pollinia. The drum-like pedicel is of the highest importance, not only by rendering the viscid dise more prominent and more likely to stick to the face of an insect whilst inserting its proboscis into the nectary beneath the stigma, but on account of its power of contraction. The pollinia lie inclined backwards in their cells (see Cuap. IL WABENARIA CHLORANTHA. 71 fig. A), above and some way on each side of the stig- matic surface; if attached in this position to the head of an insect, the. insect might visit any number of flowers, and no pollen would be left on the stigma. But observe what takes place : in a few seconds after the inner end of the drum-like pedicel has been removed from its embedded position and exposed to the air, one side of the drum contracts, and this contraction draws the thick end of the pollinium inwards, so that the caudicle and the viscid surface of the disc are no longer parallel, as they were at first, and as they are repre- sented in the section, fig. C. At the same time the drum rotates through nearly a quarter of a circle, and this moves the caudicle downwards, like the hand of a clock, depressing the thick end of the pollinium or mass of pollen-grains. Let us suppose the right-hand disc to be affixed to the right side of an insect’s face, and by the time required for the insect to visit another flower on another plant, the pollen-bearing end of the pollinium will have moved downwards and inwards, and will now infallibly strike the viscid surface of the stigma, situated in the middle of the flower beneath and between the two anther-cells. The little rudimentary tail of the caudicle projecting _ beyond the drum-like pedicel is an interesting point to those who believe in the modification of species ; for it shows us that the disc has been carried a little inwards, and that primordially the two discs stood even still further in advance of the stigma than they do at present. We thus learn that the parent-form ap- proached in this respect the structure of that extra- ordinary Orchid, the Bonatea speciosa of the Cape of Good Hope. The remarkable length of the nectary, containing much free nectar, the white colour of the corspicuous 72 OPHREZ. Crap. IL flowers, and the strong sweet odour emitted by them at night, all show tnat this plant depends for its fertilisa- tion on the larger nocturnal Lepidoptera. I have often found spikes with almost all the pollinia removed. From the lateral position and distance of the two viscid discs from each other, the same moth would generally remove only one pollinium at a time; and in a spike which had not as yet been much visited, three flowers had both pollinia, and eight flowers had only one pollinium removed. From the position of the discs it might have been anticipated that they would adhere to the side of the head or face of moths; and Mr. F. Bond sent me a specimen of Hadena dentina with one eye covered and blinded by a disc, and a specimen of Plusia v. aureum with a disc attached to the edge of the eye. Mr. Marshall* collected twenty specimens of Cucullia wmbratica on an island in Der- wentwater, separated by half-a-mile of water from any spot where H. chlorantha grew; nevertheless, seven of these moths had the pollinia of this Orchid affixed to their eyes. Although the discs are so adhesive that almost all the pollinia in a bunch of flowers which was carried in my hand and thus shaken were removed by adhering to the petals or sepals, yet it is certain that moths, probably the smaller species, often visit these flowers without removing the pollinia; for on examining the discs of a large number of pollinia whilst still in their cells I found minute Lepido- pterous scales glued to them. The cause of the flowers of various kinds of Orchids being constructed so that the pollinia are always affixed to the eyes or proboscides of Lepidoptera, and to the naked foreheads or proboscides of Hymenoptera, * ‘Nature,’ Sept. 12, 1872, p. 393. Cuap, II, MABENARIA BIFOLIA. 73 no doubt is that the viscid discs cannot adhere to a scaly or very hairy surface; the scales themselves being easily detached. Variations in the structure of the flower of an Orchid, unless they led to the viscid discs touching some part of the body of an insect where they would remain firmly attached, would be of no service, but an injury to the plant; and consequently such variations would not be preserved and perfected. Habenaria bifolia, or Lesser Butterfly Orchis—I am aware that this form and the last are considered by Mr. Bentham and by some other botanists as mere varieties of one another ; for it is said that intermediate gradations in the position of the viscid discs occur. But we shall immediately see that the two forms differ in a large number of other characters, not to mention general aspect and the stations inhabited, with which we are not here concerned. Should these two forms be hereafter proved to graduate into each other, independently of hybridisation, it would be a remarkable case of variation; and I, for one, should be as much pleased as surprised at the fact, for these two forms certainly differ from one another more than do most species belonging to the same genus. The viscid discs of the Lesser Butterfly Orchis are oval, and face each other. They stand far closer together than in the last species; so much so, that in the bud, when their surfaces are cellular, they almost touch. They are not placed so low down relatively to the mouth of the nectary. The viscid matter is of a somewhat different chemical nature, as shown by its much greater viscidity, if after having been long dried it is moistened, or after being kept in weak spirits of wine. The drum-like pedicel can hardly be said to be present, but is represented by a longitudinal ridge, truncated at the end where the caudicle is v4 OPHRE &. Cuar. IL attached, and there is hardly a vestige of the rudi- mentary tail. In fig. 12 the discs of both species, of the proper proportional sizes, are represented as seen vertically from above. The pollinia, after removal from their cells, undergo nearly the same movements as in the last species. In both forms the movement is well shown by removing a pollinium by the thick end with a pair of pin- cers, and holding it under the microscope, when the plane of the viscid disc will be seen to move through an angle of at least forty-five degrees. The caudicles of the Lesser Butterfly Orchis are relatively very much shorter than in the other species; the little packets of pollen are shorter, whiter, and, in a mature flower, separate much more readily from one another. Lastly, the stigmatic surface is differently shaped, being more plainly tripartite, with two lateral prominences, situ- ated beneath the viscid discs. These prominences contract the mouth of the nectary, making it sub- quadrangular. Hence I cannot doubt that the Larger and Lesser Butterfly Orchids are distinct species, masked by close external similarity.* As soon as I had examined the present species, Fig. 12. BSBA B. Disc and caudicle of H. chlo- rantha, seen from above, with the drum-like pedicel fore-shortened. A. Dise and caudicle of H. bi- folit, seen from above. * According to Dr. H. Miiller, Iabenaria or Platanthera bifolia of English authors is the P. sol- stitialis of Buenninghausen ; and he fully agrees with me that it must be ranked as specifically distinct from P. chlorantha. Dr. Miiller states that this latter species is connected by a series of gradafions with another form which in Germany is called P. bifolia. He gives a very full and interesting account of the varia- bility of these three forms of Platanthera, and of their structnra in relation to their manner of fer- tilisation: ‘Verhandl. d. Nat. Verein. f. Pr. Rh. u. Westfal’ Jabrg. xxv. IIL, Folge, v. Bd. pp. 36-38. Cuar. IL. PLATANTHERA, 75 I felt convinced, from the position of the viscid dises, that it would be fertilised in a different manner from the Larger Butterfly Orchis; and now, owing to the kindness of Mr. F. Bond, I have examined two moths, namely, Agrotis segetwm and Anaitis plagiata, one with three pollinia, and the other with five pollinia, attached, not to the eyes and side of the face as in the last species, but to the base of the proboscis. I may remark that the pollinia of these two species of Habe- naria, when attached to moths, can be distinguished at a glance. Professor Asa Gray has described* the structure of no less than ten American species of Platanthera. Most of them resemble in their manner of fertilisation the two British species; but some of the species, in which the viscid discs do not stand far apart, have curious contrivances, such as a channelled labellum, lateral shields, &c., compelling moths to insert their proboscides directly in front. P. hookeri, on the other hand, differs in a very interesting manner: the two viscid discs stand widely separated from each other ; consequently a moth, unless of gigantic size, would be able to suck the copious nectar without touching either disc ; but this risk is avoided in the following manner : —the central line of the stigma is prominent, and the labellum, instead of hanging down, as in most of the other species, is curved upwards, so that the front of the flower is made somewhat tubular and is divided into halves. Thus a moth is compelled to go to the one or other side, and its face will almost certainly be brought into contact with one of the discs. The drum of the pollinium, when removed, contracts in the same manner as I have described under P. chlorantha. *“¢ American Journal of Science,’ vol. xxxiv. 1862, pp. 118, 259, and 424, aud vol. xxxvi. 1863, p. 292, 76 OPHREZ. Cuap. II. Professor Gray has seen a butterfly (Nisoniades) from Canada with a pollinium of this species attached to each eye. In the case of P. flava, moths are compelled in a different manner to enter the nectary on one side. A narrow but strong protuberance, rising from the base of the labellum, projects upwards and backwards, so as almost to touch the column; thus the moth, being forced to go to either side, is almost sure to withdraw one of the viscid discs. P. hyperborea and dilatata have been regarded by some botanists as varieties of the same species; and Professor Asa Gray says that he was formerly tempted to come to the same con- clusion; but on closer examination he finds, besides other characters, a remarkable physiological difference, namely, that P. dilatata, like its congeners, requires insect aid and cannot fertilise itself; whilst in P. hyperborea the pollen-masses commonly fall out of the anther-cells whilst the flower is very young or in bud, and thus the stigma is self-fertilised. Nevertheless, the various structures adapted for crossing are still present.* The genus Bonatea is closely allied to Habenaria, and includes plants having an extraordinary structure. Bonatea speciosa is an inhabitant of the Cape of Good Hope, and has been carefully described by Mr. Trimen ;t but it is impossible to explain its structure without drawings. It is remarkable from the manner in which the two stigmatic surfaces, as well as the two viscid discs, project far out in front of the flower, and from the complex nature of the labellum, which consists of seven, or probably of nine distinct parts all fused * Mr. J. Mansel Weale bas de- _ poll ‘nia not undergoing any movo- scribed (‘Journ. Lin, Soc. Bot.’ ment or change of position when vol. xiii. 1871, p. 47) the method of removed from their cases. fertilisation of two South African + ‘Journ. Lian. Soc. Bot! vol species of Habenaria: one of ix. 1865, p. 156. these is remarkable from the Cuar. II. BONATEA SPECIOSA. 77 together. As in Platanthera flava, there is a process at the base of the labellum which compels moths to enter the flower on either side. The nectary, accord- ing to Mr. Trimen and Mr. J. Mansel Weale, does not contain free nectar; but the latter author believes that the tissue of which it is composed tastes sweet, so that moths probably penetrate it for the sake of the intercellular fluid. The pollinia are of astonishing length, and when removed from their cases hang down merely from the weight of the pollen-masses, and if attached to the head of an insect would be in a proper position for adhering to the stigma. Mr. Weale has likewise described some other South African species of Bonatea.* These differ from B. speciosa in having their nectaries full of nectar. He found a small butterfly, Pyrgus elmo, “ perfectly embarrassed by the number of pollinia of this Bonatea attached to its sternum.” But he does not specify whether the sternum was naked or covered with scales. The South African genera Disa and Disperis are placed by Lindley in two sub-tribes of the Ophree. The superb flowers of Disa grandiflora have been described and figured by Mr. Trimen.t The posterior sepal, instead of the labellum, is developed into a large nectary. In order that insects may reach the copiously stored nectar, they must insert their proboscides on either side of the column; and in accordance with this fact the viscid discs are turned outwards in an extraordinary manner. The pollinia are crooked, and when removed bend downwards from their own weight, so that no movement is necessary for placing themselves in a proper position. Considering the large supply of * ¢ Journ. Linn. Soc. Bot.’ vol. ¢ ‘Journ. Linn. Soc. Bot.’ vol. x. p. 470. vii. 1863, p. 144. 78 . OPHRES. Cuar. IL nectar and that the flowers are very conspicuous, it is remarkable that they are rarely visited by insects. Mr. Trimen wrote to me in 1864 that he had lately examined seventy-eight flowers, and only twelve of these had one or both pollinia removed by insects, and only five had pollen on their stigmas. He does not know what insects occasionally fertilise the flowers ; but Mrs. Barber has more than once seen a large fly, allied to Bombylius, with the pollinia of Disa polygnoides attached to the base of its proboscis. Mr. Weale states* that D. macrantha differs from D. grandiflora and cornuta in producing plenty of seed, and is remarkable from often fertilising itself. This follows from “avery slight jerk, when the flower is fully expanded, sufficing to eject the pollinia from their widely open anther-cases, and to bring them into contact with the stigma. This in nature is not unseldom the case, as I have repeatedly found many flowers thus fertilised.” He has, however, no doubt that the flowers are likewise cross-fertilised by nocturnal insects. He adds that D. grandiflora in being so seldom fertilised by insects offers a case like that of Ophrys muscifera; whilst D. macrantha in being often self-fertilised closely cor- responds with Ophrys apifera; but this latter species seems to be invariably self-fertilised. Lastly, Mr. Weale has described,{ as far as he could make out, the manner in which a species of Disperis is fertilised by the aid of insects. It deserves notice that the labellum and two lateral sepals of this plant secrete nectar. We have now finished with the Ophrex; but before passing on to the following tribes, I will recapitulate * ‘Journ. Linn. Soc, Bot.’ vol. + ‘Journ. Linn Soe. Bot.’ vol. xiii, 1871, p. 45. - xiii. 1871, p. 42. Cnr. IL. OPPRE, 79 the chief facts with respect to the movements of the pollinia, all due to the nicely regulated contraction of that small portion of membrane (together with the pedicel in the case of Habenaria) lying between the layer or ball of adhesive matter and the extremity of the caudicle. In a few cases, however, as with some of the species of Disa and Bonatea, the caudicles when removed from their cells do not undergo any movement ; the weight of the pollen-masses sufficing to depress them into a proper position. In most of the species of Orchis the stigma lies directly beneath the anther-cells, and the pollinia simply move vertically downwards. In Orchis pyramidalis there are two lateral and inferior stigmas, and the pollinia move downwards and outwards, diverging to the proper angle, so as to strike the two lateral stigmas. In Gymnadenia the pollinia move only downwards, but they are adapted for striking the lateral stigmas, by being attached to the upper lateral surfaces of the proboscides of Lepidoptera. In Nigri- tella they move upwards, but this depends merely on their being always affixed to the lower side of the proboscis. In Habenaria the stigmatic surface lies beneath and between the two widely-separated anther- cells, and the pollinia here converge, instead of diverg- ing as in Orehis pyramidalis, and likewise move down- wards. A poet might imagine that whilst the pollinia were borne through the air from flower to flower, adhering to an insect’s body, they voluntarily and eagerly placed themselves in that exact position, in which alone they could hope to gain their wish aud perpetuate their race. 80 ARETHUSEE. Cuar, IIL CHAPTER III. ARETHUSEZ, Cephalanthera grandiflora; rostellum aborted; early penetration of the pollen-tubes; case of imperfect self-fertilisation ; cross-fertilisation effected by insects which gnaw the labellum—Cephalanthera ensi- folia—Pogonia—Pterostylis and other Australian orchids with the labellum sensitive to a touch—Vanilla—Sobralia. \ Cephalanthera grandiflora.—This Orchid is remark- able from not possessing a rostellum, which is so eminently characteristic of the order. The stigma is large, and the anther stands above it. The pollen is extremely friable and readily adheres to any object. The grains are tied together by a few weak elastic threads; but they are not cemented together, so as to form compound pollen-grains, as in almost all other Orchids.* In this latter character and in the complete abortion of the rostellum we have evidence of degrada- tion; and Cephalanthera appears to me like a degraded Epipactis, a member of the Neottez, to be described in the next chapter. The anther opens whilst the flower is in bud and partly expels the pollen, which stands in two nearly free upright pillars, each nearly divided longitudinally into halves. These subdivided pillars rest against or even overhang the upper square edge of the stigma, which rises to about one-third of their height (see front * This separation of the grains by Lindley in his magnificent was observed, and is represented, ‘Illustrations of Orchidaccous by Bauer in the plate published Plants.’ Cuap. I. CEPHALANTHERA GRANDIFLORA. 81 view B, and side view O, in fig. 13). Whilst the flower is still in bud, the pollen-grains which rest against the upper sharp edge of the stigma (but not those in the upper or lower parts of the mass) emit a multitude of CEPHALANTUERA GRANDIPLORA. a anther; in the front view, B, ; A. Oblique view of perfect flower, the two cells with the included when fully expanded. pollen are seen. | B. Front view of column, with all v. one of the two lateral rudimen- | the petals and sepals removed. tary anthers, or auricles. C, Side view of coiumn, with all the stigma. narrow pillars of pollen (p) distal portion of the labellum. between the anther and stigma can just be seen. Diasec! ft . Masses of pollen. | sepals and petals removed; the | | tubes ; and these deeply penetrate the stigmatic tissue. After this period the stigma bends a little forward, and the result is that the two friable pillars of pollen are drawn a little forward and stand almost completely free 5 82 ARETHUSER, Cuar. (1. from the anther-cells, being tied to the edge of the stigma and supported by the penetration of the pollen- tubes. Without this support the pillars would soon fall down, The flower stands upright, with the lower part of the labellum turned up parallel to the column (fig. A). The tips of the lateral petals never become separated ;* so that the pillars of pollen are protected from the wind, and as the flower stands upright they do not fall down from their own weight. These are points of much importance to the plant, as otherwise the pollen would have been blown or fallen down and been wasted. The labellum is formed of two portions; when the flower is mature, the small triangular distal portion turns down at right angles to the basal portion ; and thus offers a small landing-place for insects in front of the triangular entrance, situated half-way up the almost tubular flower. After a short time, as soon as the flower is fully fertilised, the small distal portion of the labellum rises up, shuts the triangular door, and again perfectly encloses the organs of fructification. Although I have often searched for nectar within the cup of the labellum, I have never found even a trace. The terminal portion of the labellum is frosted with globular papille of an orange colour, and within the cup there are several transversely wrinkled, longi- tudinal ridges of a darker orange tint. These ridges are often gnawed by some animal, and I have found minute, bitten-off fragments lying within the base of the cup. In the summer of 1862 the flowers were visited less frequently by insects than is usual, as shown by the unbroken state of the pollen-masses ; nevertheless, * Baver figures the flowers say is that I have not seen them much more widely expanded than _ in this condition. is here represented : all that I can Cuapr. ILI. CEPHALANTHERA GRANDIFLORA. 83 out of seventeen flowers which were examined one day, five had their ridges gnawed, and on the next day, seven out of nine other flowers were in this state. As there was no appearance of slime, I do not believe that they had been attacked by slugs; but whether they had been gnawed by winged insects, which alone would be effectual for cross-fertilisation, J know not. The ridges had a taste like that of the labellum of certain Vande, in which tribe (as we shall hereafter see) this part of the flower is often gnawed by insects. Cephalanthera is the only British Orchid, as far as I have observed, which attracts insects, by thus offering to them solid food. The early penetration of the stigma by a multitude of pollen-tubes, which were traced far down the stigmatic tissue, apparently gives us another case, like that of the Bee Ophrys, of perpetual self-fertilisation. I was much surprised at this fact, and asked myself: Why does the distal portion of the labellum open for a short period ? what is the use of the great mass of pollen above and below that layer of grains, the tubes of which alone penetrate the upper edge of the stigma? The stigma has a large flat viscid surface; and during several years I have almost invariably found masses of pollen adher- ing to its surface, and the friable pillars by some means broken down. It occurred to me that, although the flowers stand upright, and the pillars are well pro- tected from the wind, yet that the pollen-masses might ultimately topple over from their own weight, and so fall on the stigma, thus completing the act of self-fer- tilisation. Accordingly, I covered with a net a plant having four buds, and examined the flowers as soon as they had withered ; the broad stigmas of three of them were perfectly free from pollen, but a little had fallen on one corner of the fourth. With the exception of hd st ARETHUSEZ. Crap. ILL the summit of one pillar in this latter flower, all the other pillars still stood upright and unbroken. I looked at the flowers of some surrounding plants, and every- where found, as I had so often done before, broken-down pillars and masses of pollen on the stigmas. From the usual state of the pillars of pollen, as well as from the gnawed condition of the ridges on the labellum, it may be safely inferred that insects of some kind visit the flowers, disturb the pollen, and leave masses of it on the stigmas. We thus see that the turning down of the distal portion of the labellum, by which a temporary landing-place and an open door are afforded,—the upturned labellum, by which the flower is made tubular so that insects are compelled to crawl close by the stigmatic surface,—the pollen readily cohering to any object, and standing in friable pillars protected from the wind,—and, lastly, the large masses of pollen above and below that layer of grains, the tubes of which alone penetrate the edge of the stigma,— are all co-ordinated structures, far from useless; and they would be quite useless if these flowers were always self-fertilised. To ascertain how far the early penetration of the upper edge of the stigma by the tubes of those grains which rest on it, is effectual for fertilisation, I covered up a plant, just before the flowers opened, and removed the thin net as soon as they had begun to wither. From long experience I am sure that this temporary cover- ing could not have injured their fertility. The four covered flowers produced seed-capsules as fine in ap- pearance as those on any of the surrounding plants. When ripe, I gathered them, and likewise capsules from several of the surrounding plants, growing under similar conditions, and weighed the seed in a chemical balance. The seeds from the four capsules on the Cuap, III. CEPHALANTHERA GRANDIFLORA. 85 uncovered plants weighed 1°5 grain; whilst those from an equal number of capsules on the covered plant weighed under 1 grain; but this does not give a fair idea of the relative difference of their fertility, for I observed that a great number of the seeds from the covered plant consisted of minute and shrivelled husks. Accordingly I mixed the seeds well together, and took four little lots from one heap and four little lots from the other heap, and, having soaked them in water, com- pared them under the microscope: out of forty seeds from the uncovered plants there were only four bad ones, whereas out of forty seeds from the covered-up plants there were at least twenty-seven bad; so that there were nearly seven times as many bad seeds from the covered plants, as from those left free to the access ‘of insects. We may therefore corclude that this orchid is constantly self-fertilised, although in a very imperfect manner; but this would be highly useful to the plant, if insects failed to visit the flowers. The penetra- tion of the pollen-tubes, however, is apparently even more serviceable by retaining the pillars of pollen in their proper places, so that insects, in crawling into the flowers, may get dusted with pollen. Self-fertilisation also may, perhaps, be aided by insects, carrying pollen from the same flower on to the stigma; but an insect thus smeared with pollen could hardly fail likewise to cross the flowers on other plants. From the relative position of the parts, it seems indeed probable (but I omitted to prove this by the early removal of the anthers, so as to observe whether pollen was brought to the stigma from other flowers) that an insect would more frequently get dusted by crawling out of a flower than by crawling into one; and this would of course facilitate a cross between distinct individuals. Hence 86 ARETHUSE.E. Cuar. LIL. Cephalanthera offers only a partial exception to the rule that the flowers of Orchids are generally fertilised by pollen from another plant. Cephalanthera ensifolia.—According to Delpino,* the flowers of this species are visited by insects, as shown by the removal of the pollen-masses. He believes that this is effected by their bodies being first rendered sticky by means of the stigmatic secretion. It is not clear whether the flowers also fertilise themselves. Each pollen-mass is divided into two, instead of being merely sub-divided, so that there are four distinct pollen-masses. Pogonia ophioglossoides.—The flowers of this plant, an inhabitant of the United States, resemble, as described by Mr. Scudder, t those of Cephalanthera in not having a rostellum, and in the pollen-masses not being furnished with caudicles. The pollen consists of powdery grains not united by threads. Self-fertilisation seems to be effectually prevented ; and the flowers on distinct plants must intercross, for each plant generally bears only a single flower. Pterostylis trullifolia and longifolia—I may here briefly mention some Orchids, inhabitants of Australia and New Zealand, which are included by Lindley in the same family of the Arethusez with Cephalanthera and Pogonia, and are remarkable from their labella being extremely sensitive or irritable. Two of the petals and one of the sepals form a hood which encloses the column, as may be seen at A in the accompanying figure of Pterostylis longifolia. The distal portion of the labellum affords a landing- place for insects, in nearly the same manner as with Cephalanthera; but when this organ is touched it rapidly springs up, carrying with it the touching insect, * «