THE VARIOUS CONTRIVANCES BY WHICH. ORCHIDS ARE FERTILISED BY INSECTS WELLCOME INSTITUTE LIBRARY Coll. weiMOmec Call No. qK \Vl-lh THE VARIOUS CONTRIVANCES BY WHICH ORCHIDS ARE FERTILISED BY INSECTS. By CHAELES DARWIN, M.A., F.R.S. SECOND EDITION, REVISED. FIFTH THOUSAND. WITH ILLUSTRATIONS. LONDON: JOHN MURRAY, ALBEMARLE STREET. 1890. The right of Translation is reserved. WORKS BY THE SAME AUTHOR, THE LIFE AND LETTERS OF CHARLES DARWIN. With an Autobiographical Chapter. Edited by his Son, Francis Darwin. Seventh Thousand. Portraits. 3 vols. 8vo. 36s. Murray. A NATURALIST’S JOURNAL OF RESEARCHES INTO the Natural Htstory and Geology of Countries visited dnriDg a Voyage Hound the World. Thirtieth Thousand. Woodcuts. 3s. 6cZ. Murray. THE ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION ; or. The Preservation of Favoured Haof.s in tiie struggle for Life. 6s., or Large Type Edition, 2 vols. 12s. Murray. THE VARIOUS CONTRIVANCES BY WHICH ORCHIDS ARE FERTILIZED BY INSECTS. Fifth Thousand. 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With a Study of Ms Scientific Works. Portrait. 7s. 6 d. Murray. THE STRUCTURE AND DISTRIBUTION OF CORAL REEFS. Second Edition, revised. Smith, Elder, & Co. GEOLOGICAL OBSERVATIONS ON VOLCANIC ISLANDS AND ON PARTS OF SOUTH AMERICA, visited during the Voyage of H.M.S. ‘ Beagle.’ Second Edition. Smith, Elder, £ Co. GEOLOGICAL OBSERVATIONS ON SOUTH AMERICA. Smith, Elder, & Co. A MONOGRAPH OF THE CIRRIPEDIA. With numerous Illustrations. 2 vols. 8vo. Ray Society. Hardwicke. A MONOGRAPH OF THE FOSSIL LEPADIDiE, OR PEDUNCULATED CIRRIPEDS OF GREAT BRITAIN. PALAtOXTOGRAl’HICAL SOCIETY. A MONOGRAPH OF THE FOSSIL BALANID2E AND VERRUC1D.E OF GREAT BRITAIN. Paideontogeaphical Society. FACTS AND ARGUMENTS FOR DARWIN. By Fritz Muller. From the German, with Additions by the Author. Translated by W. S. Dallas, F.L.S. Illustrations. 6s. Murray. LONDON: PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, STAMFORD STREET AND CHARING CROSS. PREFACE TO THE SECOND EDITION. The first edition of this work was published early in the year 1862, and has 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 Muller 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 Orchidece 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 Catasetidse. The account of their structure and of the action of the several parts will, I think, be intelligible, if he will first glance at the explanation of the terms given at the close of the Introduction. ( vii ) List of Papers and Books hearing on the Fertilisation of the Orchidese, which have been published since the appearance of the First Edition of this Work in 1862, arranged in Chronological Order. Bronx, H. G. — £ Charles Darwin, iiber die F.inrichtungen zur Be- fruchtung britischer und auslandischer Orchideen.’ With an Appendix by the Translator on Stanhopea devoniensis. Stuttgart, 1862. Gray, Asa. — On Platanthera (Babenarid) and Gymnadenia in 4 Enumeration 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 hooker i, in a review of the first edi- tion of the present work. — American Journal of Science and Arts, vol. xxxiv. July 1862, p. 143. Anderson, J. — ‘ Fertilisation of Orchids.’ — Journal of Horticulture and Cottage Gardener, April 21, 1863, p. 287. Gosse, P. H. — 4 Microscopic Observation on some Seeds of Orchids.’ — Journal of Horticulture and Cottage Gardener, April 21, 1863, p. 287. Gray, Asa. — On Platanthera ( Ptabernaria ) Jlava and Gymnadenia tridentata. — American Journal of Science and Arts, vol. xxxvi. Sept. 1863, p. 292. Journal of Horticulture and Cottage Gardener. — March IT, 1863, p. 206. ‘On Orchid Cultivation, Cross-breeding, and Hybridising.’ Scudder, J. H. — On Pogonia ophioglossoides. Proceedings of the Boston Society of Natural History, vol. ix. April, 1863. Treviranus. — ‘Ueber Dichogamie nach C. C. Sprengel und Ch. Darwin. § 3. Orchideen.’ — Botanische Zeitung, No. 2, 1863, p. 9. TUI LIST OF PAPERS AND BOOKS. Treviranus. — 1 Nachtragliche Bemerkungen iiber die Befruchtung einiger Orchideen.’ — Botanische Zeitung, No. 32, 1863, p. 241. Trimen, B. — ‘On tlie Fertilisation of Disa grandiflora, Linn.’ — Journal of Linnean Society, Botany, vol. vii. 1863, p. 144. West of Scotland Horticultural Magazine. — ‘ Fertilisation of Orchids,’ Sept. 1863, p. 65. Cruger. — ‘ A few Notes on the Fecundation of Orchids, and their Morphology.’ — Journal of Linnean Society, Botany, vol. viii. No. 31, 1864, p. 127. Scott, J. — ‘ On the Individual Sterility and Cross-impregnation of certain Species of Oucidium.’ — Journal of Linnean Society, vol. viii. No. 31, 1864, p. 162. Moggridge, J. Traherne. — ‘ Ohs rvations on some Orchids of the South of France.’ — Journal of Linnean Society, Botany, vol. viii. No.32, 1865, p. 256. Trimen, B. — ‘ On the Structure of Bonatea speciosa, Linn., with reference to its Fertilisation.’ — Journal of Linnean Society, vol. ix. 1865, p. 156. Rohrbach, P. — ‘Ueber Epipogium gmelini .’ — Gekronte Preisschrift, Gottingen, 1866. Delpino. — ‘ Sugli Apparecchi della Fecondazione nelle Piante antocarpee.’ Florence, 1867. Hildebrand, F. — ‘Die Geschlechter-Vertheilung hei den Pflanzen,’ &c. Leipzig, 1867, p. 51, et seq. Hildebrand, F. — ‘ Frederigo Delpino’s Beobachtungen iiber die Bestaubungsvorrichtungen bei den Phanerogamen.’ — Bota- nische Zeitung, No. 34, 1867, p. 265. Moggridge, J. Traherne, on Ophrys. — ‘Flora of Mentone,’ 1867 (?). Plates 43, 44, 45. Weale, J. P. Mansel. — ‘ 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. Hildebrand. — ‘ Notizen iiber die Geschlechtsverhaltnisse brasili- anischer Pflanzen. Aus einem Briefe von Fritz Miiller.’ — Botanische Zeitung, No. 8, 1868, p. 113. LIST OF PAPERS AND BOOKS. IX Muller, Fritz. — * Ueber Befruchtungserscheinungen bei Orchi- deen.’ — Botanische Zeitung, No. 39, 1868, p. 629. Muller, Hermann.—1 Beobachtungen an westfalishen Orchideen.’ — Yerhandlungen des nat. Yereins flir Pr. Rheinl. u. Westf. 1868 and 1869. Darwin, Charles. — ‘ Notes on the Fertilisation of Orchids.’ — Annals and Magazine of Natural History, Sept. 1869. Delpino. — ‘ Ulteriori Osservazioni sulla Dicogamia nel Regno vege- tale.’ Parte prima. Milan, 1868-69, pp. 175-78. Moggridge, J. Traherne. — ‘ Ueber Ophrys insectifera, L. (part). — Verhandlungen der Kaiserl. Leop. Carol. Akad. (Nova Acta), tom. xxxv. 1869. Muller, Fritz. — ‘ Qeber einige Befruchtungserscheinungen.’ — Botanische Zeitung, No. 14, 1869, p. 224. Muller, Fritz. — ‘Umwandlung von Staubgefassen in Stempel bei Begonia. Uebergang von Zwitterbliithigkeit in Getrenntblii- thigkeit bei Chamissoa. Triandrische Varietiit eines monan- drischen Epidendrum.’ — Botanische Zeitung, No. 10, 1870, p. 149. Weale, J. P. Mansel. — ‘ Note on a Species of Disperis found on the Kageberg, South Africa.’ — Journal of Linnean Society, Botany, vol. xiii. 1871, p. 42. Weale, J. P. Mansel.— ‘ Some Observotions on the Fertilisation of Disci macrantha .’ — Journal of Linnean Society, vol. xiii. 1871, p. 45. Weale, J. P. Mansel. — ‘ Notes on some Species of Habenaria found in South Africa.’ — Journal of Linnean Society, vol. xiii. 1871, p. 47. Cheeseman, T. F. — ‘ On the Fertilisation of the New Zealand Species of Pterostylis.’ — -Transactions of the New Zealand Insti- tute, vol. v. 1873, p. 352. Muller, Hermann. — ‘ Die Befruchtung der Blumen durch Insekten,’ &c. Leipzig, 1873, pp. 74-86. Cheeseman, T. F. — ‘On the Fertilisation of Acianthus cyrtostiHs' — Transactions of the New Zealand Institute, vol. vii. 1874 (issued 1875), p. 349. X LIST OF PAPERS AND BOOKS. Muller, Hermann. — ‘ Alpine Orchids adapted to Cross-fertilisation by Butterflies.’ — Nature, Dec. 31, 1874. Delrino. — ‘ Ulteriori Osservazioni sulla Dicogamia nel Regno vegetale.’ Parte seconds, fasc. ii. Milan, 1875, pp. 149, 150. Lubbock, Sir J. — £ British Wild Flowers.’ London, 1875, pp. 162- 175. Fitzgerald, R. D. — ‘ Australian Orchids.’ Part I. 1875, Part II. 1876. Sydney, New South Wales. Introduction Pages 1-5 CHAPTER I. OPHRE^E. 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 II. OPHEE7E — 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 CONTENTS. Nil CHAPTER III. ARETHUSE2E. 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 ensifolia — Pogonia — Pterostylis and other Australian orchids with the labellum sensitive to a touch — Vanilla — Sobralia Pages 80-92 CHAPTER IV. NE0TTE2E. 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; sensitiveness 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 — Thelv mitra, self-fertile 93-12? CHAPTER V. MALAXEZE AND EPIDENDREiE . Malaxis paludosa — Masdevallia, 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- dendrese 128-148 CONTENTS. X1U CHAPTER VI. YANDEX. 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 oi fertilisation — Angraecum sesquipedale, wonderful length of nec- tary— Species with the entrance into the stigmatie chamber much contracted, so that the pollen-masses can hardly be inserted — Coryanthes, extraordinary manner of fertilisation Pages 149-177 CHAPTER YII. vande.33 continued. — catasetid.®. Catasetkhe, the most remarkable of all Orchids — The mechanisrr by which the pollinia of Catasetum are ejected to a distance ana are transported by insects — Sensitiveness of the horns of the rostellum — Extraordinary difference in the male, female, and hermaphrodite forms of Catasetum tridentatum — Monnodes ignea, curious structure of the flowers ; ejection of the pollinia — Mormodes luxata — Cycnoches ventricosum, manner of fer- tilisation 178-225 CHAPTER VIII. CYPRIPEDE2E — 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 Orchideae — Wonderful amount of modification which they have undergone 226-246 XIV CONTENTS. 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 Page 247-293 LIST OF WOODCUTS, 1*AG H 1. Orchis mascula 8 2. „ „ pollinia of 12 3. Orchis pyramid alis 18 4. Moth’s head and proboscis, with attached pollinia 31 5. Ophrys muscifera 46 6. „ aranifera 50 7. „ arachnites 51 8. „ apifera 53 9. PeRISTYLUS VIRIDIS 62 10. Gymnadenia conopsea 65 11. IIabenaria ciilorantha 69 12. PoLLINIA OF IIABENARIA CHLORANTHA AND BIFOLIA .. 74 13. Cephalanthera grandiflora 81 14. Pterostylis longifodta 87 15. Epipactis palustris 94 16. „ LATIFOLIA 101 17. Spiranthes autumnalis 107 18. Listera oyata .. .. 116 19. Malaxis paludosa 130 20. Masdevallia fenestrata 136 21. Dendrobium chrysanthum 139 22. Cattleya , 144 23. Diagram illustrative of the structure of the VANDE2E 150 24. PoLLINIA OF Yande® 154 25. Pollinium of Ornithocephalus 160 XVI LIST OF WOODCUTS. 20. Calanthe masuca 27. CoRYANTIIES SrECIOSA Catasetum saccatum 29. f 30. Catasetum tridentatum 31. Monachantecjs and Myanthus 32. Moemodes ignea 33. Cycnoches ventkicosum 34. „ „ SECTION THROUGH BUD .. 35. Cypripedium 36. Transverse section of flower of an Orchid 37. Rostellum of Catasetum 33. Disc of Gymnadenia conopsea 161 174 1182 (183 194 199 209 222 223 227 236 256 272 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, &c. &c. INTKO DUCT ION. The object of tbe 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, I 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 B 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. I 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- In this memoir Waetcher, who servazioni sulla Dicogamia,’ Part does not seem to have been ac- ii. 1875, p. 150) a memoir by Waet- quainted with Sprengel’s work, cher, published in 1801 in Roe- shows that insects are necessary mer’s 1 Archiv fiir die Botanik,’ t. for the fertilisation of various ii. p. 11, which apparently has re- orchids, and describes well the mained unknown to everyone else. wonderful structure of Neottia. 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 to 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 * 1 Linnean Transactions,’ 1833, vol. xvi. p. 704. B 2 4 INTRODUCTION. 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, sc 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 disc;’ but in many exotic species the portion removed is so INTRODUCTION. 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 disc, together in some cases with the pedicel. Lastly, the three outer divisions of the flower are 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 labellum, 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 OPHREiE. Chap I. i CHAPTER I. OPHREiE. Structure of 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, 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. Throughout the following volume I have followed, as far as I conveniently could, the arrangement of the Orchidese given by Lindley. The British species belong to five of his tribes, the Ophreae, ISTeottese, Arethusese, Malaxeae and Cypripedese, 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 Orchidese. The ninth chapter is devoted to miscellaneous and general considerations. The Ophreae 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 ( 0 . masctda). The sepals and the petals have been re- moved, excepting the labellum with its nectary. The Chap. I. ORCHIS MASCULA. 7 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 packets 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 eaudicle (c, C). The end of the caudiele 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 dies 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 Orchis mascula. Chap. I. ORCHIS MASCULA. 9 Description of Fig. 1. a. anther, consisting of two cells. r. rostellum. s. stigma. 1. labellum. n. sectary. р. pollen-mass. с. caudicle of pollinium. 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. C. 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 caudicle of one pollinium, lip not depressed. F. Packets of pollen-grains, tied together by elastic threads, here extended. (Copied from Bauer.) 10 OPHRE2E. Chap. I. 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 Chap. I. 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 OPHREiE. Chap. 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 B A. Pollen-mass of 0. mascula, when I B. Pollen-mass of 0. masoula, 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 Chap. I. OllCHIS 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.f 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. Muller (‘ Die Befruch- flowers of Orchis mascula, and tung der Blumen durch Insekten,’ finds that this statement is correct. 1873, p. 84) has timed humble- f ‘ Transactions of the Linnean bees at work on the spikes of Society,’ vol. xvi. p. 731. 14 OPHKB^E. Chap. 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 Chap. I. 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 Bornbus muscorum ; and Dr. H. Muller * has seen four other species of Bornbus 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 0. 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. Muller and myself visiting the flowers of Orchis morio. On some of the * ‘ Dio Befruchtung,’ &c., p. 81. 16 0PHRE2E. Chap. I. hive-bees from ten to sixteen pollen-masses adhered , to the head of Eucera longicornis eleven, to the head of Osmiarufa several, and several to the bare surface close above the mandibles of Bombus muscorum. H. Muller 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 0. inaculata , and saw many specimens of a fly (Empis livadi) 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 antennae. 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. Muller 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 Chap. I. ORCHIS PYRAMIDALI3. 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 0. mascula and its allies. There are two quite distinct rounded stigmatie 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 0. 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 continuous with the rest of the surface. The disc is partially hidden and kept damp (which is of great importance) 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 0. 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. c 18 OPHREiE, Chap. I. Fig. 3. Orciiis pyramidalis. Chap. L ORCHIS PYRAMID AXIS. 19 Descriptiox of Fig. 3. a. aether. s,s. stigma. r. rostellum. 1. labellum. V. guiding plate on the labellum. n. 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 disc 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 OPHRE2E. Chap. 1, 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 (l1, 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) Chap. 1. * ORCHIS PYRAMIDALIS. 21 between the guiding ridges of the labellum, or insert a fine bristle, and it is conducted safely to the ndnute 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 0PHRE2E. Chap. 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 0. masoula 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 Chap. I. t 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 disc would become attached obliquely, and after the compounded movement of the pollinia they would not strike the two lateral stigmatie surfaces. Then we have the rostellum partially closing the mouth of the nectary, like a trap placed in a run for 24 OPHRE2E. Chap. L 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 * Tlie late Prof. Treviranus lias but points out two unimportant confirmed (‘ Botanische Zeitung,’ inaccuracies in the drawing which. 1863, p. 241) all my observations, I have given. CllAP. I. ORCHIS USTULATA. 25 fly to another plant, and thus effect a union between two distinct individuals. Orchis ustulata * resembles 0. 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 0. 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 0. pyramidalis, might be converted into a single one, by becoming at first slightly lobed like that of 0. 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 Eimantoylossum ) 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 * I am greatly indebted to Mr. kindness in supplying me witli G. Chichester Oxenden of Broome living plants, and information re- Park fur fresh specimens of this garding many of the rarer British Orchis, and for his never-tiring Orchids. 26 0PHREJ3. Chap I. 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 0. 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 front part being thus separated from the hinder part by an abrupt step. Acer as* ( 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 0. pyramidalis and hircina. 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.f The pollinia are attached to a single viscid disc. When they are removed they do not diverge as in 0. pyramidalis , but converge and then undergo the * The separation of this genus occurrence of numerous hybrids, is evidently artificial. It is a true naturally produced, between this Orchis, but with a very short Aceras and Orchis galeata. nectary. Dr. Weddell has de- f ‘ Joum. Linn. Soc. Bot.’ scribed (‘Annales des Sc. Nat.,’ vol. viii. 1865, p. 256. He gives 3 ser. Bot. tom. xviii. p. 6) the also a figure of Orchis hircina. Chap. 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. — Mr. Moggridge 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. Muller * 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,’ Dec. 31, 1874, p. 169. 28 OPHKEiE. Chap. 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. Muller 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 morio 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. But it should be observed that when only a very few flowers remain open on the summits of the spikes, these are no longer conspicuous, ClIAI . I. FERTILISED BY INSECTS. 29 and would consequently be rarely visited by insects. I then looked at tbe 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 Muller, who, as he informs me, applied the pollen-masses of Orchis pyramidalis (44), fusca (6), militaris (14), variegata (3), coriophora (6), morio (4), maculatcc (18), mascula (6), latifolia (8), incarnata (3), Oplirys muscifera (8), Gymnadenia conop- sea (14), albida (8), Herminium monorchis (6), Epipogon aphyllus (2), Epipadis latifolia (14), palustr is (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 Muller* have proved * An abstract of their observa- ticalion,’ chap. xvii. 2nd edit. vol. tions is given in my ‘Variation of ii. p. 114. Animals and Plants under Domes- 30 OPHREiE. Chap. 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 t 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. Muller to hold good with many of the Orcbidete 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. t M. Meniere (in ‘Bull. Bot. Soc. de France,’ tom. i. 1854, p. 370) says he saw in Dr. Gue'pin’s collection, bees collected at Sau- mur with the pollinia of Orchids attached to their heads; and he states that a person who kept bees near the Jardin de la Faculte' (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. Chap. I. FEKTILISED BY INSECTS. 31 Polyommatus alexis. Lycsena plilaeas. Arge galathea. Hesperia sylvanus. „ linea. Syrichthus alveolus. Antlirocera filipendulae. „ trifolii.* Lithosia complana. Leueania lithargyria (two speci- mens). Caradrina blanda. „ alsines. Agrotis cataleuca. A large majority of these moths and butterflies had two or three pairs of pollinia attached to them, and invariably to the proboscis. The Acontia had seven pair (fig. 4), and the Fig. 4.. Caradrina no less than eleven pair ! The proboscis of this latter moth presented an ex- traordinary arborescent ap- pearance. The saddle-formed discs, each bearing a pair of pollinia, adhered to the pro- boscis, one before the other, with perfect Symmetry ; and Head and proboscis of Acontia luc- F „ p ,i tuosa with seven pair of pollinia this follows from the moth of Orchis pyramidalis attached having always inserted its to the iiroboscis- 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 Eubolia mensuraria (two speci- mens). Hadena dentina. Heliothis marginata (two speci- mens). Xylophasia sublustris (two speci- mens). Euclidia glyphica. Toxocampa pastinum. Melanippe rivaria. Spilodes palealis. „ cinctalis. Acontia luctuosa. * I am indebted to Mr. Parfitt erroneously thought to belong to for an examination of this moth, Ophrys apifera. The pollen bad which is mentioned in the ‘ En- changed from its natural green tomologist’s Weekly Intelligencer,’ colour to yellow; on washing it, vol. ii. p. 182, and vol. iii. p. 3, however, and drying it, the green Oct. 3, 1857. The pollinia were tint returned. 32 0PHRE2E. Chap. L 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 Uadena 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 Epipadis 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 0. maculata. On the other hand fifteen plants of Oplirys muscifera had not one pollen-mass there removed. Malaxis 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 * ‘ Gardeners’ 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- deners’ Chronicle,’ 1860, p. 528. Chat1. I. 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. i 6 3 2 . 3 A 1 1|| * a | ~ ®a «'fl Oi if a £ o CD c c a *!*■§• glSS-eii ° c .-3 = *.s c — « o «*-< A o glsl umber only o moved are in columi i~, The flowers were all mature . . ) 50 27 119 Orchis fusca. Two plants. S. Kent.) 8 54 Flowers quite mature, and even withered) Aceras anthropophora. Four plants. S.) Kent J 63 6 34 D u 0PHRE7E. Chap. I. In tlie second lot of 0. 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 0. pyramida/tis 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 0. 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 0. 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 ing fertilised ; and on this occasion was a very wet one, I gathered six only 119 flowers produced cap- unusually fine spikes of 0. pyra - suits, 183 having failed to do so. midalis. These bore 302 flowers, ' S;x spikes of 0. macula ta bore 187 excluding fourteen which were still flowers, of which eighty-two pro- fully expanded and capable of be- duced capsules, 105 having failed. CiiAr. L 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 0. fyramidalis ; whereas, as we shall here- after see, the Bee Ophrys is independent of insects. Many spikes of 0. latifolia were examined, because, being familiar with the usual state of the closely-allied 0. 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, 0. maculata had 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 0. 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 0. latifolia, neither of which had been sufficiently visited by insects, there were more flowers with one pollinium than with both removed. I casually examined many D 2 0PHRE2E. Chap. I. 86 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 0. fusca is so rare a species in Britain from not being- sufficiently attractive to insects, and to its not producing a sufficiency of seed. C. K. Sprengel* noticed, that in Germany 0. militaris (ranked by Bentham as the same species with 0. fusca) is likewise imperfectly fertilised, but more perfectly than our 0. 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 0. latifolia and morio, and could never find a drop of nectar; nor could Krunitzf find nectar * ‘Das entdeckte Geheimniss,’ tung der Nektarien,’ 1833, s. 28. etc. s. 404. See also ‘Das entdeckte Gtheim- t Quoted by J. G. Kr.rr in his niss,’ s. 403. * Untersuchungen iiber die Bedeu- ■Chat. I. SECRETION OF NECTAR. 37 either in the nectary or on the labellum of 0. 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 0. 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 kind? 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 0. pyramidalis, ana 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 0PHKE2E. Chap. I, dicates that moths do not go to wcrk in a quite sense- less manner.* Nature may he said to have tried this same experi- ment, but not quite fairly ; for Orchis pijramidalis, 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 fifteen flowers of Gi/mnadenia ccmopsew, and they did not produce a single capsule : he also treated in the same man- ner fifteen flowers of Platanthera or Habenavia 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 boro only one capsule. Similar experi- ments made by him on Gymna- denia seem to me open to doubt. t ‘ Handbook of the British Flora,’ 1858, p. 501. Ciiai\ 1. SECRETION OF NECTAR. 39 and I determined to examine 0. morio rigorously. As soon as many dowers 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 dowers which had lately had their pollinia removed by insects, of which fact I had independent proof on one occasion by dnding grains of some foreign pollen within the nectary ; and 1 took other dowers, 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 drst edition of this work, I one day saw various kinds of bees visiting repeatedly the dowers 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 0. viaculata at a time when I repeatedly saw dies of the genus Empis keeping theb- 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 0. morio and maculata, and especially of 0. pyramidalis and lnrcina, 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 ot the inner membrane, which could be penetrated very easily, — and, lastly, at the quantity of duid contained 40 OPHREiE. Chap. L between the two membranes. So copious is this fluid, that, after cutting off the extremities of the nectaries of 0. 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 nectaries 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 nectar up to one-third or two-thirds of their length. The inner membrane presented the same structure and was covered with papillae 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. Chap. I. 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. Muller is also convinced* that insects puncture the thickened bases of the standard petals of the Laburnum,! and perhaps the 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. PI. Muller, who has often watched bees at work on several species of Orchis, 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 Befruclitung,’ &c. p. 235. t Treviranus confirms (‘ Bot. Zeitung,’ 1863, p. 10) a statement made by Salisbury, that when the filaments in the flowers of another leguminous plant, Edwardsia, fall off, or when they are cautiously separated, a large quantity of sweet fluid flows from the points of separation ; and as beforehaud there was no trace of any such fluid, 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. Soc. Bot. de France,’ tom. i. 1851, 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 homologically an ex- terior surface. X ‘ Die Befruclitung,’ &c. p. 84. § ‘ Ult. Osservazioni sulla Di- cogamia,’ 1875, p. 121. 42 OPHREiE. Chai1. I. 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 0. 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 0. metadata, 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 0. 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 to another flower. Can it be believed that bees which CiiAr. 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 Ophrea3,. namely, in Gymnadenia conopsea and cdbida, 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 OPHRE.E. Chap. 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 Gijinncidenia conopsea the disc remained sticky for two hours, and in Habenaria chlorantha for more than twenty-four hours. In Peristylus viriciis 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. Chap. II. OrHRYS MUSCIFERA. 45 CHAPTER II. ophrete — continued. Fly and Spider Ophrys — Bee Ophrys, apparently adapted for perpetual self-fertilisation, but with paradoxical contrivances for intercrossing — Herminium monorchis, attachment of the pollinia to the front legs of insects — Periatylus 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 — Uisa — Summary on the powers ot movement in the pollinia. The 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 modification of the dorsal stigma and pistil ; so that in (Jphrys 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- lum 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 OPHREzE. Chap. II. 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. Opiirys muscifera, op. Fly Opiirys. a. anther. s. stigma. r, r. rostella. 1. labellum. A. Flower viewed in front : the two upper petals are almost cylin- drical and hairy : the two ros- tella stand a little in advance of the bases of the anther-cells ; but this is not shown from the foreshortening of the drawing. B. One of the two pollinia removed from its anther-cell, and viewed 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, Ohap. II. OPHRYS MUSCIFE11A. 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 I 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 OPHEEiE. Chap. 1.1, dS apart, and project over tlie 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. Since the publication of the second edition in 1877, Hermann Muller has made the interesting observa- tion* that the labellum of the Fly Ophrys is occa- sionally covered with drops of an excreted fluid, and in one instance he actually saw a fly ( Sarcovhaya , sp.) seated on the labellum and licking up the drops of fluid. The fly flew away without removing the pol- linia ; but if he had not been disturbed it is probable that he would have moved on and tried the sham nectaries of Sprengel, in which case he won Id have come in contact with the sticky disc of the pollen masses, and would thus have been able to effect the fertilisation of the next flower which he might visit. Number of Flowers. Both Pollinia or one removed by Insects. Both Pollinia In their Cells. In 1858, 17 plants, bearing 57 flowers,! growing near each other were examined/ In 1858, 25 plants growing in another! 30 27 15 50 spot, and bearing 65 flowers . . / In 1860, 17 plants, bearing 61 flowers In 1861, 4 plants from S. Kent, bearing 241 28 33 flowers (all the previous plants having! grown in N. Kent) . . . . ) 15 9 Total 8S 119 That insects visit the flowers of the Fly Ophrys and remove the pollinia, though not effectually or su£2» • ‘Nature,’ 1878, p. 221, January 27. "Chap. II OPHKYS MUSCIFEKA. 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 in 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, hut 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 E 50 ©PIIEE2E. Chap. 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. c. species. Whilst the pollinia r 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 li a form from the corresponding Ophrys aranifera. part of the caudicle of 0. mUS- A. Pollinium before the act of cifera ; but the upper part (A, B. Pollinium after the act of fiff* b) 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 clamp ; 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 pouch-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. Dicegamia,’