NATIONAL SOCIETY'S DEPOSITORY. WESTMINSTER A •-, • v-"*.. r% v v • -NJT v • * CHAPTERS IN POPULAR NATURAL HISTORY. BY SIR JOHN LUBBOCK, BART, M.P., F.R.S., D.C.L., LL.D., PRES. LINN. SOC., ETC., ETC., ETC. ARRANGED AS AN ADVANCED READING BOOK FOR USE IN ELEMENTARY AND HIGHER SCHOOLS. LONDON : NATIONAL SOCIETY'S DEPOSITORY, SANCTUARY, WESTMINSTER. [All rights reserved, ,] LONDON : HARRISON AND SONS, PRINTERS IN ORDINARY TO HER MAJESTY. ST. MARTIN'S LANE. PREFACE. THE National Society has done me the honour to propose to republish parts of some of my Natural History Lectures adapted as a Reading Book. Those who may wish to pursue the subjects further, I would refer to my " Origin and Metamor- phoses of Insects" (Macmillan and Co.), "British Wild Flowers," &c. (Macmillan and Co.), " Scientific Lectures" (Macmillan and Co.), and "Ants, Bees, and Wasps" (Paul, Trench, and Co.). I am greatly indebted to my publishers for their courtesy in allowing me to reprint here part of the above-mentioned works. I have also to thank Messrs. Paul, Trench, and Co., Messrs. Macmillan and Co., Messrs. Cassell and Co., and Messrs. Lovel Reeve and Co., for the use of various illustrations, which they have been so good as to place at my disposal. HIGH ELMS, DOWN, KENT. December, 1882. 2090901 CONTENTS. SECTION I. PAGE ANTS J l 'J.'-!^"*. .-"'"'- 1'J.X' •>• .'£IO: i SECTION II. BEES AND WASPS 63 . . : : ' '• . SECTION III. THE COLOURS OF ANIMALS ... ' "i..1 ... "" 74 SECTION IV. ON FLOWERS AND INSECTS ... » .^ •oj»j-x;;^lj^t» ••• II2 SECTION V. ON PLANTS AND INSECTS ... " .« J 1.. * 155 .' } t.'iiB H^ SECTION VI. FRUITS AND SEEDS 169 LIST OF ILLUSTRATIONS. FIG. 1. The Slave-making or Amazon Ant (Polyergus rufescens). 2. Larva, Chrysalis, and Cocoon of the Horse Ant (Formica rufa). After Blanchard. 3. The Horse Ant (Formica rufa) : Male, Female, and Worker. After Blanchard. 4. The Mexican Honey Ant (Myrmecocystus mexicanus). After Blanchard. 5. The Sauba Ant (Oecodoma cephalotes]. Two sisters. 6. The Rose Aphis (Aphis ROSCE). After Blanchard. 7. A Root-feeding Aphis. 8. The White Woodlouse (Platyarthrus hojfmanseggii) + to. After Spence Bate. 9. Claviger. After Shuckard. 10. The Slave Ant (Formica fusca). 11. The Caterpillar of the Marbled White Butterfly (Arge galathea). After Weissmann. 12. The Caterpillar of the Eyed Hawk-moth (Smerinthus ocel- latus). After Weissmann. 13. The Caterpillar of the Elephant Hawk-moth (Ch&rocampa elpenor). Full grown, natural size. After Weissmann. 14. The Caterpillar of the Elephant Hawk -moth (Charocavipa elpenor). First Stage. After Weissmann. 15. The Caterpillar of the Elephant Hawk-moth (Charocampa elpenor}. Second Stage. After Weissmann. 1 6. The Caterpillar of the Elephant Hawk-moth (Charocampa elpenor). Just before the second moult. After Weissmann. 17. The Caterpillar of the Elephant Hawk-moth (Cha:rocampa elpenor). Third Stage. After Weissmann. vf List of Illustrations. FIG. 1 8. The Caterpillar of the Elephant Hawk-moth (Charocampa elpenor). Fourth Stage. After \Veissmann. 19. The Caterpillar of the Elephant Hawk-moth. (Charocampa elpenor). Fifth Stage. After Weissmann. 20. The Caterpillar of the Small Elephant Hawk-moth (Ckarocamj 'a porcellus}. After Weissmann. 21. White Deadnettle (Lamium album). After Bentham. 22. Flower of White Deadnettle (Lamium album). 23. Section of the Flower of White Deadnettle (Lamium album}. 24. Meadow Geranium (Geranium pratense). After Bentham. 25. Common Sundew (Drosera rotundijolia}. After Bentham. 26. Common Bladderwort (Utricularia vulgaris). After Bentham. 27. Broad Dock (Rumex obtusifolius). After Bentham. 28. Common Willow Herb (Epilobium anguslifolium). After Bentham. 29. Common Mallow (Malva sylvestris). After Sowerby. 30. Dwarf Mallow (Malva rotundifolia}. After Sowerby. 31. Stamens and Stigmas of the Common Mallow (Malva sylves- tris). After Miiller. 32. Stamens and Stigmas of the Dwarf Mallow (Malva rotundifoha}. After Miiller. 33. Common Willow Herb (Epilobium angustifolium). After Sowerby. 34. Hoary Willow Herb (Epilobium parviflorum}. After Sowerby. 35. Meadow Geranium (Geranium pratense). Young flower and older flower. After Hildebrand. 36. Common Arum (Arum maculatuni). Diagrammatic section. 37. Sage (Salvia qffidnalis). Section of a young flower. After Ogle. 38. Sage (Salvia ojficinalis} visited by a Bee. After Ogle. 39. Sage (Salvia officinalis). Section of an older flower. After Ogle. 40. Stamens of Sage (Salvia qffidnalis) in their natural position. After Ogle. 41. Stamens of Sage (Salvia ojficinalis) when moved by a Bee. After Ogle. 42. Wild Chervil (Charophyllum sylvestre). After Bentham. 43. Floret of Feverfew ( Chrysanthemum partheniuni). Just opened. After Ogle. L ist of Illustrations. v i i FIG. 44. Floret oi Feverfew {Chrysanthemum parthenium}. Somewhat more advanced. After Ogle. 45. Floret of Feverfew (Chrysanthemum parthenium). With the stigmas expanded. After Ogle. 46. Bird's-foot Trefoil (Lotus corniculatus). After Bentham. 47. Flower of Bird's-foot Trefoil (Lotus corniculatus), seen from the side and in front. After Milller. 48. Flower of Bird's-foot Trefoil (Lotus corniculatus), after removal of the standard. After Miiller. 49. Flower of Bird's-foot Trefoil (Lotus corniculatus}, after removal of the standard and wings. After Miiller. 50. Flower of Bird's-foot Trefoil (Lotus corniculatus'), after removal of one side of the keel. After Miiller. 51. Flower of Bird's-foot Trefoil (Lotus corniculatus}. Terminal portion of fig. 50, more magnified. After Miiller. 52. Common Cowslip (Primula veris}. After Bentham. 53. Section of the Flower of Primula. Long-styled form. 54. Section of the Flower of Primula. Short-styled form. 55. Common Carlina (Carlina vulgaris}. After Kerner. 56. Knautia dipsacifolia. After Kerner. 57. Flower of Linnoea. After Kerner. 58. Amphibious Polygonum (Polygonum amphibium}. After Bentham. 59. -Nottingham Catchfly (Silene nutans). After Bentham. 60. Nottingham Catchfly (Silene nutans}. After Kerner. 61. John Go-to- Bed-at-Noon ( Tragopogon pratense}. After Bentham. 62. Valisneria (Valisneria}. 63. Hairy Bittercress (Cardamine hirsuta}. After Bentham. 64. Hairy Violet ( Viola hirta}. 65. Dog Violet ( Viola canina}. 66. Dog Violet ( Viola canina}. Seed-vessel open and showing seeds. 67. Dog Violet ( Viola canina). Seed-vessel after ejecting the seeds. 68. Herb Robert (Geranium Robertianum). 69. Cut-leaved Geranium (Geranium dissectum}. Diagram. 70. Herb Robert (Geranium Robertianum}. Diagram. 71. Wood Vetch (Vicia syhatica}. viii List of Illustrations. FIG. 72. Pod of Bush Vetch ( Vicia sepium). After Bentham. 73. Fruit of the Squirting Cucumber (Ecballium). 74. Poppy-head (Papaver). 75. Seeds or Fruits of the Maple, Sycamore, Lime, Hornbeam, Elm, Birch, Pine, Fir, Ash. 76. Fruits or Seeds of the Willow Herb (Epilobiuni), Hawkbit (Thrincia kirla), Tamarix, Willow (Salix), Cotton-grass (Eriophorum), Bullrush ( Typha}. 77. Lesser Duckweed (Lemna minor). After Bentham. 78. Seeds or Fruits of Burdock (Lappa), Agrimony (Agrimonia), Bur Parsley (Caucalis), Enchanter's Nightshade (Ctrtcza), Cleavers (Galittm), Forget-me-not (Myosotis). 79. Fruits of Harpagophyton procumbens and Martynia proboscidea. Natural size. 80. Seed of Myzodendron. After Hooker. 81. Cardamine chenopodifolium. 82. Vetch ( Vicia amphicarpa). 83. Pea (Lathyrus amphicarpos). 84. Seed of Crane's Bill (Erodium). 85. Seed of Stipa pennata. Natural size. 86. Seeds of Corydalis. 87. Pods of Scorpiurus subvillosa and Scorpiurus vermiculata. 88. Pod of Biserrula. 89. Seed of Castor Oil Plant. 90. Seed of Jatropha. CHAPTERS IN POPULAR NATURAL HISTORY. Fig. i. — THE SLAVE-MAKING ANT. SECTION I.-ANTS. I. 1. THERE is no animal or plant which would not well repay long and careful study. Yet all are by no means equally interesting. Some specially de- B 2 Ants. serve attention from their utility to man, some from their power of inflicting injury. Among insects there are few, if any, whose habits are more interesting than those of Ants. They live in large communities : they build houses ; they make roads ; some of them, as we shall presently see, keep other insects, just as we keep cows ; and some of them even have slaves. In this country we have rather more than thirty kinds ; but ants become more numerous in species, as well as in individuals, in warmer countries, and more than a thousand species are known. Even this large number is certainly far short of those actually in existence. 2. No two species of ants are identical in habits ; and, on various accounts, their mode of life is far from easy to unravel. Most of their time is passed underground ; all the tending of the young, for instance, is carried on in the dark. I have for some years kept many nests of various species under observation, and these have given me special facilities for observing the internal economy of ant life. Another main difference between my observations and those of previous naturalists has consisted in the careful record of the actions of individual ants. The most convenient mode of marking them was, I found, a small dab of paint on the back. 3. The life of an ant falls into four well-marked periods — those of the egg, of the larva or grub Ants. 3 (fig. 2, a a'\ of the pupa or chrysalis (fig. 2, b b'} and of the perfect insect or imago. The eggs arc white or yellowish, and somewhat elongated. Fig. 2.— Larva (a a'), Chrysalis (bb'), and Cocoon (c and a head or anther, in which the pollen is produced ; and fourthly, a pistil, which is situated in the centre of the flower, and consists generally of three principal parts : one or more compartments at the base, each containing one or more seeds ; the stalk or style ; and the stigma, which in many familiar instances forms a small head at the top of the style or ovary, and to which the pollen must find its way in order to fertilise the flower. 3. At the close of the last century, Conrad Sprengel, a German schoolmaster, published a valu- able work on flowers, in which he pointed out that the forms and colours, the scent, honey, and general structure of flowers, have reference to the visits of insects, which are of importance in transferring the pollen from the stamens to the pistil. This admir- able work, however, did not attract the attention it deserved, and remained almost unknown until Mr. Darwin devoted himself to the subject. Our illustrious countryman was the first clearly to per- ceive that the essential service which insects perform to flowers, consists not only in transferring the pollen from the stamens to the pistil, but in trans- ferring it from the stamens of one flower to the pistil of another. Sprengel had indeed observed in more than one instance that this was the case, but he did not altogether appreciate the importance of the fact. I 2 1 1 6 On Flowers and Insects. 4. Mr. Darwin, however, has not only made it clear from theoretical considerations, but has also proved it, in a variety of cases, by actual experiment. More recently Fritz Miiller has even shown that in some cases pollen, if placed on the stigma of the same flower, has no more effect than so much in- organic dust. In by far the majority of cases, the relation between flowers and insects is one of mutual ad- vantage. In some plants, however — as, for instance, in our Common Sundew — we find a very different state of things, and the plant catches and devours the insects. The first observation on insect-eating flowers was made about the year 1768 by our countryman Ellis. He observed that in a certain North American plant the leaves have a joint in the middle, and thus close over, kill, and actually digest any insect which may alight on them. 5. In our common Sundew (fig. 25) the rounded leaves are covered with hairs, which are swollen and glutinous at the tip. Of these hairs there are on an average about 200 on a full-sized leaf. The tips of the hairs are each surrounded by a drop of an exceedingly viscid solution, which, glittering in the sun, has given rise to the name of the plant. If any object be placed on the leaf, these glandular hairs slowly fold over it, and en- close it. If, for instance, any small insect alights on the leaf it becomes entangled in the glutinous secretion, the glands close over it, their secretion is, On Flffwers and Insects. 117 increased, and they literally digest their prey. It has been recently shown that plants supplied with insects grow more vigorously than those not so fed. If, on the other hand, a small stone, or any other substance which contains no nourishment, be placed on the leaf, though the hairs at first close over it, they soon open again. It is very Fig. 25. — COMMON SUNDEW (Drosera rotundifolia). curious that while the glands are so sensitive that an object weighing only y-^j-j^th of a grain placed on them is sufficient to cause motion, yet they are "insensible to the weight and repeated blows of drops" of even heavy rain. 6. The Sundew, however, is not our only English insectivorous plant. In the Butterwort, which fre- On Floivers and Insects. qucnts' moist places, generally on mountains, the leaves are concave with incurved margins, and the upper surfaces are covered with two sets of glan- dular hairs. In this case the naturally incurved edges curve over still more if a fly or other insect be placed on the leaf. 7. Another case is that of the Bladderwort Fig. 26. — COMMON BLADDERWORT (Utricularia vulgaris). (fig. 26), an aquatic species, which bears a number of little bags which have been supposed to act as floats. Branches, however, which bear nobladderfloat just as well as the others, and there seems no doubt that the real use of these little bags is to capture small aquatic animals, which they do in considerable numbers. The bladders, in fact, are on the prin- On Floivers and Insects. 119 ciple of an eel-trap, having an entrance closed with a flap which permits an easy entrance, but effec- tually prevents the unfortunate victim from getting out again. 8. I will only allude to one foreign case, that of the Sarracenia. In this genus some of the leaves are in the form of a pitcher. They secrete a fluid, and are lined internally with hairs pointing down- wards. Up the outside of the pitcher there is a line of honey glands, which lure the insects to their des- truction. Flies and other insects which fall into this pitcher cannot get out again, and are actually digested by the plant. Bees, however, are said to be scarcely ever caught. 1 20 On Flowers and Insects. II. 1. Everyone knows how important flowers are to insects ; every one knows that bees, butterflies, &c., derive the main part of their nourishment from the honey or pollen of flowers, bnt comparatively few are aware, on the other hand, how much the flowers themselves are dependent on insects. Yet it has, I think, been clearly shown that if insects have been in some respects modified and adapted with a view to the acquirement of honey and pollen, flowers, on the other hand, owe their scent and honey, their form and colour, to the agency of insects. Thus the lines and bands by which so many flowers are ornamented have reference to the position of the honey ; and it may be observed that these honey-guides are absent in flowers which open at night, where they of course would not show, and would therefore be useless. Flowers, more- over, which are generally pale — for instance, the White Lychnis — open in the evening ; while those of a deeper hue, such as the Red Lychnis, flower by day. 2. Indeed, it may be laid down as a general rule, that those flowers which are not fertilised by honey- seeking insects — as, for instance, those of the Dock (fig. 27), the Beech, and most other forest trees — On Flowers and Insects. 121 are small in size, and do not possess either colour, scent, or honey. Though the pistil is generally surrounded by a row of stamens, there are comparatively few cases in which the pollen of the latter falls directly on the former. On the contrary, this transference is in most cases effected in other ways, generally Fig. 27. — BROAD DOCK (Rumex obtusifolius). by means of the wind, of insects, or, in some cases, of birds. In the former case, however, by far the greater part of the pollen is wasted ; and much more must therefore be produced than in those cases where it is carried by insects. 3. One advantage, of course, is the great economy of pollen. We have not much information on the 122 On Flowers and Insects. subject, but it would seem, from the few observa- tions that have been made, that half a dozen pollen grains are sufficient to fertilise a seed. But in plants in which the pollen is carried by the wind, the chances against any given grain reaching the pistil of another flower are immense. Consequently by far the greater part of the pollen is lost. Every one, for instance, must have observed the clouds of pollen produced by the Scotch Fir. In such flowers as the Paeony the pollen is carried by insects, and far less therefore is required ; yet even here the quantity produced is still large; it has been esti- mated that each flower produces between 3,000,000 and 4,000,000 grains. The Dandelion is more spe- cialised in this respect, and produces far less pollen, about 240,000 grains to each flower ; while in the common Avens only ten times more pollen is pro- duced than is actually used in fertilisation. 4. It might, however, be at first supposed that where stamens and pistil co-exist in the same flower, the pollen from the one could easily fall on and fertilise the other. And in fact this does occur in some species ; but, as we have seen, it is a great advantage to a species that the flower should be fertilised by pollen from a different stock. How then is self-fertilisation prevented ? There are three principal modes. Firstly, in many plants the stamens and pistil are in separate flowers, sometimes situated on different plants. On Flowers and Insects. 123 Secondly, even when the stamens and pistil are in the same flower, they are in many species not mature at the same time; this was first observed by Sprengel as long ago as 1790; in some cases the stigma has matured before the anthers are ripe, while in other and more numerous cases the anthers have ripened and shed all their pollen before the stigma has come to maturity. Thirdly, there are many species in which, though the anthers and stigma are contained in the same flower and are mature at the same time, they are so situated that the pollen can hardly reach the stigma of the same flower. 5. The transference of the pollen from one flower to another is, as already mentioned, effected princi- pally either by the wind or by insects. Wind-fertilised flowers, as a rule, have no colour, emit no scent, produce no honey, and are regular in form. Colour, scent, and honey are the three characteristics by which insects are attracted to flowers. As a rule, wind-fertilised flowers produce much more pollen than those which are fertilised by insects. This is necessary, because it is obvious that the chances against any given pollen grain reaching the stigma are much greater in the one case than in the other. Every one, as already mentioned, has observed the showers of yellow pollen produced by the Scotch Fir. 6. Again, it is an advantage to wind-fertilised 1 24 On Flowers and Insects. plants to flower early in the spring before the leaves are out, because the latter would catch much of the pollen, and thus interfere with its access to the stigma. Again, in these plants the pollen is less adherent, so that it can easily be blown away by the wind, which would be a disadvantage in most plants which are fertilised by insects. Such flowers generally have the stigma more or less branched or hairy, which evidently must tend to increase their chances of catching the pollen. 7. The evidence derivable from the relations of bees and flowers is probably sufficient to satisfy most minds that bees are capable of distinguishing colours, but the fact had not been proved by any conclusive experiments. I therefore tried the fol- lowing. If you bring a bee to some honey, she feeds quietly, goes back to the hive, stores away her honey, and returns with or without companions for another supply. Each visit occupies about six minutes, so that there are about 10 in an hour, and about 100 in a day. I may add that in this respect the habits of wasps are very similar, and that they appear to be quite as industrious as bees. Perhaps I may give the record of a morning's work of one of my wasps.* She came to the honey at a few minutes after 4 in the morning, and to show how regularly she worked I may give the following extract from my note-book, recording her visits from 6.30 till 12. Thus she — * In her case the intervals were rather longer than usual. On Floivers and Insects. 125 Came again )> at 6.29, 6.41 6-55 and returned at 6. 32 6.44 7 " 7.11 7-23 7-15 „ 7.26 " 7-37 7.56 742 8.3 » 8.ii 8.20 8.14 8.24 » » 8.31 8.40 8.34 8.42 5» 8.50 8.58 8.52 9 > ) 9.8 9.18 9-n 9-22 » 9-30 9-32 » J 9-39 9-40 » 9-So 9-54 » IO.I 10.5 >l 10.14 10.25 10-17 10.28 H 10.37 ,, 10.40 » 10.47 II » 10.51 n.6 > » 11.17 ,, 11.20 ,, 11-34 "•37 " 11.50 12.5 "•53 12.8 and so on till half-past 7 in the evening. Thus she worked twelve hours like a man, and performed more than 100 journeys to and fro.* This, how- * Mr. Darwin, in his last work, brought forward some striking evidence how rapidly bees work. They visit, it appears, 20 flowers in a minute, and so carefully do they economise the sunny hours, that in flowers with several nectaries if they find one dry, they do 1 26 On Flowers and Insects. ever, was in autumn ; in summer they make over- time, and work on till late in the evening. 8. I have already mentioned some experiments which show clearly that bees can distinguish colours. They appear fortunately to prefer the same colours as we do. On the contrary, flowers of a livid, yellow, or fleshy colour are most attractive to flies ; and moreover, while bees are attracted by odours which are also agreeable to us, flies, as might naturally be expected from the habits of their larvae, prefer some which to us seem anything but pleasant. not waste time by examining the others on the same plant. Mr. Darwin watched carefully certain flowers, and satisfied himself that each one was visited by bees at least thirty times in a day. The result is, that even where flowers are very numerous — as, for in- stance, on heathy plains and in clover fields — every one is visited during the day. Mr. Darwin carefully examined a large number of flowers in such cases, and found that every single one had been visited by bees. On Flowers and Insects. 12: Fig. 28. — COMMON WILLOW HERB (Epilobium angustifoliuni). III. r . Among other obvious evidences that the beauty of flowers is useful in consequence of its attracting insects, we may adduce those cases in which the transference of the pollen is effected in different manners in nearly allied plants, sometimes even in the same genus. Thus, the Common Mallow (fig. 29) and Dwarf Mallow (fig. 30), which grow in the same localities, and therefore must come into competition, are nevertheless nearly equally common. In the Common Mallow, however, where the 128 On Flowers and Insects. branches of the stigma are so arranged (fig. 31^ that the plant cannot fertilise itself, the petals are large and conspicuous, so that the plant is visited Fig. 29. — COMMON MALLOW (Malva sylvestris}. Fig. 30. — DWARF MALLOW (Malva rotundifolia}. by numerous insects; while in the Dwarf Mallow (fig. 32), the flowers of which are comparatively small and rarely visited by insects, the branches of the stigma are elongated, and twine themselves On Flowers and Insects. 129 among the stamens, so that the flower readily fertilises itself. 2. Another interesting case is afforded by the Stamen; and Stigmas of the COMMON MALLOW (Malva sylvestris) and the DWARF MALLOW {Malva rotundifolla}. Fig- 33-— COMMON WILLOW HERB (Epilobium anguslifoliuni], Willow Herbs. The Common Willow Herb (fig. 33) has large purplish flowers in conspicuous heads, and is much frequented by insects; while the K On Floivers and Insects. Hoary Willow Herb (fig. 34) has small solitary flowers, and is seldom visited by insects. Now in the former species their visits are necessary, because the stamens ripen and shed their pollen before the pistil, so that the flower is consequently incapable of fertilising itself. In the latter species, on the contrary, the stamens and pistil come to maturity at the same time. 3. Let us take another case, that of certain Gera- Fig. 34. — HOARY WILLOW HERB (Efilobium parviforum). niums. In the Meadow Geranium (fig. 35), which has a very large flower, all the stamens open, shed their pollen, and wither away, before the pistil comes to maturity. The flower cannot, therefore, fertilise itself, and depends entirely on the visits of insects for the transference of the pollen. In the Moun- tain Geranium, where the flower is not quite so large, all the stamens ripen before the stigma, but the interval is shorter, and the stigma is mature before all the anthers have shed their pollen. It is, On Flowers and Insects. therefore, not absolutely dependent on insects. In the Dove's-foot Geranium, which has a still smaller flower, five of the stamens come to maturity before the stigma, but the last five ripen simultaneously K 2 1 32 On Flowers and Insects, with it. Lastly, in the Small-flowered Geranium, which is least of all, the stigma ripens even before the stamens. Thus, then, we have a series more or less dependent on insects, from the Meadow Gera- nium to which they are necessary, to the Small- flowered Geranium which is quite independent of them ; whilst the size of the corolla increases with the dependence on insects. In those species in which self-fertilisation is pre- vented by the circumstance that the stamens and pistil do not come to maturity at the same time, the stamens generally ripen first. 4. The advantage of this is probably connected with the visits of bees. In those flowers which grow in bunches the lower ones generally open first. Consequently in any given spike the flowers are at first all staminate ; subsequently the lower ones, being the older, have arrived at the pistillate stage, while the upper ones are still staminate. Now it is the habit of bees to begin with the lower flowers of a spike and work upwards. A bee, there- fore, which has already dusted herself with pollen from another flower, first comes in contact with the pistillate flowers, and dusts them with pollen, after which she receives a fresh supply from the upper staminate flowers, with which she flies to another plant. 5. There are, however, some few species in which the pistil ripens before the stamens. One is our common Figwort. Now, why is this ? On Flowers and Insects. 133 Probably because the Figwort is one of our few flowers specially visited by wasps, the honey being not pleasing to bees. Wasps, however, unlike bees, generally begin with the upper flowers and pass downwards, and consequently in wasp flowers it is an advantage that the pistil should ripen before the stamens. But though the stamens generally ripen before the pistil, the reverse some- times occurs. Of this a very interesting case is that of the genus Aristolochia. The flower is a long tube, with a narrow opening closed by stiff hairs which point backwards, so that it much re- sembles an ordinary eel-trap. Small flies enter the tube in search of honey, but from the direction of the hairs it is impossible for them to return. Thus they are imprisoned in the flower, until the stamens have ripened and shed their pollen, by which the flies get thoroughly dusted. Then the hairs of the tube shrivel up, thus releasing the prisoners, who carry the pollen to another flower. 6. Again, in our common Arums, the lords-and- ladies of village lanes, the well-known green leaf incloses a central pillar (fig. 36) ; near the base of which are arranged a number of stigmas (st in the accompanying figure), and above them several rows of anthers (a). It might be supposed, therefore, that the pollen from the anthers would fall on and fertilise the stigmas. This, however, is not what occurs. In fact the stigmas come to maturity first, and have lost the possibility of fertilisation before 134 On Flowers and Insects, the pollen is ripe. The pollen must therefore be brought by insects, and this is effected by small flies, which enter the leaf, either for the sake of honey or of shelter, and which, moreover, when they have once entered the tube, are imprisoned by the fringe of hairs (//). When the anthers Fig. 36. — COMMON ARUM. Diagrammatic Section. h, hairs ; a, anthers ; st, stigmas. ripen, the pollen falls on to the flies, which in their efforts to escape get thoroughly dusted with it. Then the fringe of hairs withers, and the flies, thus set free, soon come out, and ere long carry the pollen to another plant. 7. Now let us return to our White Deadnettle, On Flowers and Insects. 135 and see how far we can answer the questions which I began by asking. 8. In the first place, the honey attracts insects. If there were no honey, they would have no object in visiting the flower. The bright colour is useful in rendering the flower conspicuous. The platform serves as an alighting stage for bees. The length of the tube has reference to that of their proboscis, and prevents the smaller species from obtaining access to the honey, which would be injurious to the flower, as it would remove the source of attraction for the bees, without effecting the object in view. The upper arch of the flower protects the stamens and pistil, and also presses them firmly against the back of the bee ; so that, when the bee alights on the stage and pushes its proboscis down to the honey, its back comes into contact with them. The row of small hairs at the bottom of the tube prevents small insects from creeping down the tube and stealing the honey. Lastly, the small processes on each side of the lower lip are the rudimentary representatives of parts formerly more largely developed, but which, having become use- less, have almost disappeared. 9. In the Deadnettle it would appear that the pistil matures as early as the stamens, and that cross- fertilisation is attained by the relative position of the stigma, which, as will be seen in the figure, hangs down below the stamens ; so that a bee, bearing pollen on its back from a previous visit to 136 On Flowers and Insects. another flower, would touch the pistil and transfer to it some of the pollen, before coming in contact with the stamens. In other species belonging to the same great group or family of plants, the same object is secured by the fact that the stamens come to maturity before the pistil ; they shed their pollen, and shrivel up before the stigma is mature. On Flowers and Insects. 137 IV. i. Fig. 37 represents a young flower of Sage, in which the stamens (a a) are mature, but not the pistil (/), which moreover, from its position, is un- touched by bees visiting the flower, as shown in Fig- 37- — SAGE (Salvia officinalis). Section of a young flower. fig. 38. The anthers, as they shed their pollen, gradually shrivel up ; while, on the other hand, the pistil increases in length and curves downwards, until it assumes the position shown in fig. 39, sf, where, as is evident, it must come in contact with any bee visiting the flower, and would touch just that part of the back on which pollen would be deposited by a younger flower. In this manner cross-fertilisation is effectually secured. 2. There are, however, several other curious points 138 On Flowers and Insects. in which the Sage differs greatly from the species last described. The general form of the flower, indeed, is very Fig. 38. — SAGE (Salvia officinalis] visited by a bee. Fig. 39- — SAGE (Salvia qfficinalis). An older flower, similar. We find again that, as generally in the Labiates, the corolla has the lower lip adapted as an alighting board for insects, while the arched On Flowers and Insects. 139 upper lip covers and protects the stamens and pistils. The arrangement and structure of the stamens is, however, very peculiar and interesting. As in the Deadnettle, they are four in number, but one Fig. 40. — Stamens in their natural position. Fig. 41. — Stamens when moved by a bee. pair is quite rudimentary (fig. 37, b\ In the other (a a) the two anthers, instead of being attached close together at the summit of the filament, are separated by a long movable rod, called a con- nective (figs. 40, 41, ;«), so that they can play freely on the stalk of the stamen. In a natural position, 140 On Flowers and Insects. this connective is upright, so that the one anther is situated (fig. 37) in the neck of the tube, the other under the arched hood. The lower anther, more- over, is more or less rudimentary. Now, when a bee comes to suck the honey, it pushes the lower anther out of the way with its head ; the result of which is that the connective swings round, and the upper fertile anther comes down on to the back of the bee (figs. 38 and 41), and dusts it with honey, just at the place where, in an older flower (fig. 39), it would be touched by the stigma, st. 3. At first sight it may seem an objection to this view that some species — as, for instance, the common Snapdragon — the flower of which, accord- ing to the above- given tests, ought to be fertilised by insects, is entirely closed. A little consideration, however, will suggest the reply. The Snapdragon is especially adapted for fertilisation by humble bees. The stamens and pistil are so arranged that smaller species would not effect the object. It is therefore an advantage that they should be ex- cluded, and in fact they are not strong enough to move the spring. The Snapdragon is, so to say, a closed box, of which the humble bees alone possess the key. 4. The common Heath offers us a very ingenious arrangement. The flower is in the form of an inverted bell. The pistil represents the clapper, and projects a little beyond the mouth of the bell. The stamens are eight in number, and form a circle On Flowers and Insects. 141 round it, the anthers being united by their sides into a continuous ring. Each anther has a lateral hole, but as long as they touch one another, the pollen cannot drop out. Each also sends out a long process, so that the ring of anthers is sur- rounded by a row of spokes. Now when a bee comes to suck the honey, it first touches the end of the pistil, on which it could hardly fail to deposit some pollen, had it previously visited another plant. It would then press its proboscis up the bell, in doing which it would pass between two of the spokes, and pressing them apart, would dislocate the ring of anthers ; a shower of pollen would thus fall from the open cells on to the head of the bee. 5. In many cases the effect of the colouring and scent is greatly enhanced by the association of several flowers in one bunch, or raceme ; as, for instance, in the Wild Hyacinth, the Lilac, and other familiar species. In the great family of Umbelli- fera, this arrangement is still further taken advan- tage of, as in the common Wild Chervil (fig. 42). In this group the honey is not, as in the flowers just described, situated at the bottom of a tube, but lies exposed, and is therefore accessible to a great variety of small insects. The union of the florets into a head, moreover, not only renders them more conspicuous, but also enables the insects to visit a greater number of flowers in a given time. 6. It might at first be supposed that in such small flowers as these self-fertilisation would be almost 142 On Flowers and Insects. unavoidable. In most cases, however, the stamens ripen before the stigmas. The position of the honey on the surface of a more or less flat disk renders it much more acces- sible than in those cases in which it is situated at the end of a more or less long tube. That of the Fig. 42. — WILD CHERVIL (Chczrophyllum sylvestris). Deadnettle, for instance, is only accessible to certain humble bees ; while H. Muller has recorded no less than 73 species of insects as visiting the common Chervil, and some plants are frequented by even a larger number. 7. In the Composites, to which the common Daisy and the Dandelion belong, the association of flowers On Flowers and Insects. 143 is carried so far, that a whole group of florets is ordinarily spoken of as one flower. The Daisy, for instance, is not really a flower, but a group of little flowers on a single stalk. Let us take, for instance, the common Feverfew, or large White Daisy (figs. 43, 44, 45). Each head consists of an outer row of Fig. 43. — Floret of FEVERFEW (Chrysanthemum parthenium), just opened. pistillate florets or little flowers, in which the tubular corolla terminates on its outer side in a white leaf or ray, which serves to make the flower more con- spicuous, and thus to attract insects. The central florets are tubular, and make up the central yellow part of the flower-head. Each of these florets con- tains a circle of stamens, the upper portions of 1 44 On Floivers and Insects. which are united at their edges and at the top (fig. 43), so as to form a tube, within which is the pistil. The anthers open inwards, so as to shed the pollen into this box, the lower part of which is Fig. 44. — Floret of FEVERFEW (Chrysanthemum parlhenium}, somewhat more advanced. Fig. 45- — Floret of FEVERFEW (Chrysanthemum par thenium], with the stigmas expanded. formed by the stigma, or upper part of the pistil. As the latter elongates, it presses the pollen against the upper part of the box, which at length is forced open, and the pollen is pushed out (fig. 44)- Any insect then alighting on the flower would carry off On Flowers and Insects. some of the pollen adhering to the under side of its body. The upper part of the pistil terminates in two branches (fig. 45, sf), each of which bears a little brush of hairs. These hairs serve to brush the pollen out of the tube; while in the tube the two branches are pressed close together, but at a later stage they separate, and thus expose the stigmatic surfaces (fig. 45, sf), on which an insect, coming from a younger flower, could hardly fail to deposit some pollen. The two stigmas in the ray florets of this White Daisy have no brush of hairs ; and they would be of no use, as these flowers have no stamens. 146 On Flowers and hi sects. Fig. 46.— BIRD'S-FOOT TREFOIL (Lotus corniculaius). V. i. The Leguminosae, or Pea-tribe, present a num- ber of beautiful contrivances. Let us take a com- mon little Bird's-foot Trefoil (fig. 46). The petals are five in number ; the upper one stands upright, and is known as the standard (fig. 47, std} ; the two lateral ones present a slight resemblance to wings (fig. 47, w), while the two lower ones are united along their edges, so as to form a sort of boat, whence they are known as the "keel" (figs. 48, 49, £). The stamens, with one exception, are united at their bases, thus forming a tube (figs. 50, 51, /), surrounding the pistil, which projects beyond them On Flowers and Insects. 1 47 - 47- Fig. 48. Fig. 47. — Flower ot BIRD'S-FOOT TREFOIL (Lotus corn':culatus}t seen from the side and in front. ,, 48. — Ditto, after removal of the standard. ,, 49. — Ditto, after removal of the standard and wings. ,, 50. — Ditto, after removal of one side of the keel. „ 51. — Terminal portion of fig. 50, more magnified. e, entrance to the honey ; a, the free stamen ; c, the place where the wings lock with the keel ; /, expanded ends of stamens ; jc, filaments of stamens ; g, tip of keel ; po, pollen ; st, stigma. L 2 148 On Flowers and Insects, into a triangular space at the end of the keel. Into this space the pollen is shed (fig. 5 !,/ ( Tragopogon pratense). close again before ten in the morning. Bees, however, are very early risers, while ants come out later, when the dew is off; so that it might be an advan- tage to a flower which was quite unprotected, to open early for the bees, and close again before the ants were out, thus preserving its honey exclusively for bees. Fig. 62. — VALISNERIA. a, pistillate flower ; b, staminate flower ; c, floating pollen. 169 SECTION VI.— FRUITS AND SEEDS. I. i. THOUGH technical terms are very necessary in science, I shall endeavour, as far as I can, to avoid them here. As, however, it will be impossible for me to do so altogether, I will do my best at the commencement to make them as clear as possible. In order to understand the structure of the seed, we must commence with the flower, to which the seed owes its origin. Now, if you take such a flower as, say a Geranium, you will find, as has been already explained, that it consists of the following parts : — Firstly, there is a whorl of green leaves, known as the sepals, and together forming the calyx ; secondly, a whorl of coloured leaves, or petals, generally forming the most conspicuous part of the flower, and called the corolla ; thirdly, a whorl of organs more or less like pins, which are called stamens ; and in the heads, or anthers, of which the pollen is produced. These anthers are in reality modified leaves ; in the so-called double flowers, as, for instance, in our Garden Roses, they are developed into coloured leaves like those 1 70 Fruits and Seeds. of the corolla, and monstrous flowers are not unfrequently met with, in which the stamens are green leaves, more or less resembling the ordinary leaves of the plant. Lastly, in the centre of the flower is the pistil, which also is theoretically to be considered as constituted of one or more leaves, each of which is folded on itself, and called a carpel. Sometimes there is only one carpel. Generally the carpels have so completely lost the appearance of leaves, that this explanation of their true nature requires a considerable amount of faith. The base of the pistil is the ovary, composed, as I have just mentioned, of one or more carpels, in which the seeds are developed. I need hardly say that many so-called seeds are really fruits ; that is to say, they are seeds with more or less complex envelopes. 2. We all know that seeds and fruits differ greatly in different species. Some are large, some small ; some are sweet, some bitter ; some are brightly — some dull — coloured, some are good to eat, some poisonous ; some spherical, some winged ; some covered with bristles, some with hairs ; some are smooth, and some very sticky. We may be sure that there are good reasons for these differences. 3. In the first place, then, during growth, seeds in many cases require protection. This is especially the case with those of an albuminous character. It is curious that so many of those which are luscious when ripe, as the Peach, Strawberry, Cherry. Fruits and Seeds. 171 Apple, &c., are stringy, and almost inedible, till ripe. Moreover, in these cases, the fleshy portion is not the seed itself, but only the envelope, so that even if the sweet part is eaten the seed itself remains uninjured. 4. On the other hand, such seeds as the Hazel, Beech, Spanish Chestnut, and innumerable others are protected by a thick, impervious shell, which is especially developed in the Brazil-nut, the so-called Monkey Pot, the Cocoa-nut, and other plants. In other cases the envelopes protect the seeds, not only by their thickness and toughness, but also by their bitter taste, as, for instance, in the Walnut. One genus (Mucund) is remarkable in having the pods covered with stinging hairs. 5. In many cases the calyx, which is closed when the flower is in bud, opens when the flower ex- pands ; and then, after the petals have fallen, closes again until the seeds are ripe, when it opens for the second time. This is, for instance, the case with the common Herb Robert (fig. 68). In a South European plant allied to the thistles the outer envelopes form an exquisite little cage. Another case, perhaps, is that of Nigella, or, as it is seme- times more prettily called, " Love-in-a-Mist," of old English gardens. 6. Again, the protection of the seed is in many cases attained by curious movements of the plant itself. In fact, plants move much more than is generally supposed. So far from being motionless, 172 Fruits and Seeds. they may almost be said to be in perpetual move- ment, though the changes of position are generally so slow that they do not attract attention. This is not, however, always the case. We are all familiar with the Sensitive Plant, which droops its leaves when touched. Another species has leaves like those of an Acacia, and all day the leaflets go slowly up and down. There is a sort of pea living in India which has trifoliate leaves, the lateral leaf- lets being small and narrow ; and these leaflets are perpetually moving round and round, whence the specific name gyrans. In this case the object of the movement is quite unknown to us. In Dion&a, as already mentioned (p. 1 16), the leaves form a regular fly-trap. Directly an insect alights on them they shut up with a snap. 7. In a great many cases leaves are said to sleep — that is to say, at the approach of night they change their position, and sometimes fold themselves up, thus presenting a smaller surface for radiation, and being, in consequence, less exposed to cold. Mr. Darwin has proved experimentally that leaves which were prevented from moving suffered more from cold than those which were allowed to assume their natural position. He has observed with re- ference to the arrowroot plant that, if it has had a severe shock, it cannot get to sleep for the next two or three nights. 8. The sleep of flowers is also probably a case of the same kind. These motions, indeed, have but Fruits and Seeds. 173 an indirect reference to our present subject. On the other hand, in the Dandelion the flower-stalk is upright while the flower is expanded, a period which lasts for three or four days ; it then lowers itself, and lies close to the ground for about twelve days while the fruits are ripening, and then rises again when they are mature. In the Cyclamen the stalk curls itself up into a beautiful spiral after the flower has faded. The flower of the little Linaria of our walls pushes out into the light and sunshine, but as soon as it is fertilised it turns round and endeavours to find some hole or cranny in which it may remain safely ensconced until the seed is ripe. 9. In some water-plants the flower expands at the surface, but after it is faded retreats again to the bottom. This is the case, for instance, with the Water Lilies and several other aquatic plants. In Valisneria, again, as already mentioned, the pistil- late flowers (fig. 62, a) are borne on long stalks, which reach to the surface of the water, on which the flowers float. The staminate flowers (fig. 62, b], on the contrary, have short straight stalks, from which, when mature, the pollen (fig. 62, c) detaches itself, rises to the surface, and, floating freely on it, is wafted about, so that it comes in contact with the pistillate flowers. After fertilisation, however, the long stalk coils up spirally, and thus carries the ovary down to the bottom, where the seeds can ripen in greater safety. 174 Fruits and Seeds. Fig. 63. — HAIRY BITTERCRESS (Cardaminc hirsuta}. II. I. The next points to which I will direct your at- tention are the means of dispersion possessed by many seeds. Farmers have found by experience that it is not desirable to grow the same crop in the same field year after year, because the soil becomes more or less exhausted. In this respect therefore the powers of dispersion possessed by many seeds are a great advantage to the species. Moreover, they are also advantageous in giving the seed a chance of germinating in new localities suitable to the requirements of the species. Thus, one com- Fruits and Seeds. 175 mon European species has rapidly spread over the whole of South Africa, the seeds, which are covered with hooked spines, being carried in the wool of sheep. 2. There are a great many cases in which plants possess powers of movement directed to the dis- semination of the seed. Thus, there are some funguses which grow underground, but eventually come up to the surface of the ground, split open and shed their spores* in the form of dust. I have already referred to the case of the common Dandelion. Some plants, as we shall see, even sow their seeds in the ground, but these cases will be referred to later on. 3. In other cases the plant throws its own seeds to some little distance. This is the case with the common Hairy Bittercress (fig. 63), a little plant, I do not like to call it a weed, six or eight inches high, which comes up abundantly on any vacant spot in our kitchen gardens or shrubberies. The seeds are contained in a pod which consists of three parts, a central membrane and two side walls. When the pod is ripe the walls are much stretched. The seeds are loosely attached to the central piece by short stalks. Now, when the proper moment has arrived, the outer walls are kept in place by a delicate membrane only just strong enough to * These are tiny seed-like bodies, but are termed " spores " by botanists, because in some important points they differ from true seeds. 1 76 Fruits and Seeds. resist the tension. The least touch, for instance a puff of wind blowing the plant against a neighbour, detaches the outer wall, which suddenly rolls itself up, generally with such force as to fly from the plant, thus jerking the seeds to a distance of several feet. 4. In the common Violets, besides the coloured flowers, there are others in which the corolla is either absent or imperfectly developed. The sta- mens also are small, but contain pollen, though less than in the coloured flowers. In the autumn large numbers of these curious flowers are produced. When very young they look like an ordinary flower-bud (fig. 64, a), the central part of the flower being entirely covered by the sepals, and the whole having a triangular form. When older (figs. 64 and 65, b] they look at first sight like an ordinary seed capsule, so that the bud seems to pass into the capsule without the flower stage. The Pansy Violets do not possess these interesting flowers. In the Sweet Violet and Hairy Violet (fig. 64) they may easily be found by searching among the leaves nestling close to the ground. It is often said that the plants actually force these capsules into the ground, and thus sow their own seeds. I have not, however, found this to be the case ; though, as the stalk lengthens, and the point of the capsule turns downwards, if the earth be loose and uneven, it will no doubt sometimes so Fruits and Seeds. 177 happen. When the seeds are fully ripe the capsule opens by three valves and allows them to escape. Fig. 64. — HAIRY VIOLET ( Viola hirta). a, young bud ; b, ripe seed capsule. 5. In the Dog Violet (fig. 65) the case is very different. The capsules are less fleshy, and, though hanging down when young, at maturity they erect themselves (fig. 65, c), stand up boldly above the N I78 Fruits and Seeds. Fig. 65. — DOG VIOLET (Viola canina). a, bud ; b, bud more advanced ; c, capsule open, some of the seeds are already thrown. Fig. 66.— DOG VIOLET. Seed-vessel open and showing seeds. Fruits and Seeds. 1 79 rest of the plant, and open by the three equal valves (fig. 66), resembling an inverted tripod. Each valve contains a row of three, four, or five brown, smooth, pear-shaped seeds, slightly flattened at the upper, wider end. Now the two walls of each valve, as they become drier, contract, and so approach one another, thus tending to squeeze out the seeds. These resist some time ; but at length Fig. 67. — DOG VIOLET. Seed-vessel after ejecting the seeds. the attachment of the seed to its base gives way, and it is ejected several feet, this being no doubt much facilitated by its form and smoothness. I have known even a gathered specimen throw a seed nearly 10 feet. Fig. 67 represents a capsule after the seeds have been ejected. 6. Now we naturally ask ourselves what is the reason for this difference between the species of violets ; why does the Sweet Violet conceal its cap- N 2 i8o Fruits and Seeds. sules among the moss and leaves on the ground, while the Dog Violet and others raise theirs boldly above their heads and throw the seeds to seek their fortune in the world ? If this arrangement be best for the Dog Violet, why has not the Sweet Violet also adopted it ? The reason is, I believe, to be found in the different mode of growth of these two species. The Dog Violet is a plant with an elon- gated stalk, and it is easy therefore for the capsule to raise itself above the grass and other low herbage among which violets .grow. The Sweet Violet, on the contrary, has, in ordinary parlance, no stalk, and the leaves are radical, i.e., rising from the root. This is at least the case apparently, though, botani- cally speaking, they rise at the end of a short stalk. Now, under these circumstances, if the Sweet Violet attempted to shoot its seeds, the cap- sule not being sufficiently elevated, the seeds would merely strike against some neighbouring leaf, and immediately fall to the ground. Hence, I think, we see that the arrangement of the capsule in each species is that which is most suitable to the general habit of the plant. Fruits and Seeds. 181 Fig. 68. — HERB-ROBERT GERANIUM {Geranium Robertianuni). a, bud ; b, flower ; c, flower after the petals have fallen ; J, flower with seeds nearly ripe ; e, flower with ripe seeds ; f, flower after throwing seeds. III. i. In the true Geraniums again, as for instance, in the Herb Robert (fig. 68), after the flower has faded, 1 82 Fruits and Seeds. the cen.tral axis gradually lengthens (fig. 68, c d). The seeds, five in number, are situated at the base of the column, each being enclosed in a capsule, which terminates upwards in a rod-like portion, which at first forms part of the central axis, but gradually detaches itself. When the seeds are ripe the ovary raises itself into an upright position (fig. 68, e) ; the outer layers of the rod-like termination of the seed-capsule come to be in a state of great tension, and eventually (fig. 70) detach the rod with a jerk, and thus throw the seed some little distance. Fig. 68, f, represents the central rod after the seeds have been thrown. In some species, as for instance in the Cut-leaved Geranium (fig. 69), the capsule- rod remains attached to the central column and the seed only is ejected. 2. It will, however, be remembered that the cap- sule is, as already observed, a leaf folded on itself, with the edges inwards, and in fact, in the Geranium, the seed-chamber opens on its inner side. You will, therefore, naturally observe to me that when the carpel bursts outwards, the only effect would be that the seed would be forced against the outer wall of the carpel, and that it would not be ejected, oecause the opening is not on the outer but on the inner side. Your remark is perfectly just, but the difficulty has been foreseen by our Geraniums, and is overcome by them in different ways. In some species, as for instance in the Cut-leaved Geranium, a short time before the opening of the pods, the Fruits and Seeds. 183 seed-chamber places itself at right angles to the pillar (fig. 69, a). The edges then separate, but they are provided with a fringe of hairs, just strong enough to retain the seed in its position, yet suffici- ently elastic to allow it to escape when the carpels Diagram. Fig. 69.— THE CUT-LEAVED GERANIUM. just before throwing seed ; b, just after throwing seed ; c, the capsule still attached to the rod ; , subterranean pods. VI. I . Even among terrestrial species there are many cases in which plants are not contented simply 2 1 0 Fruits and Seeds. to leave their seeds on the surface of the soil, but actually sow them in the ground. Thus in the Subterranean Clover, one of our rarer kinds, only a few of the florets become per- fect flowers, the others form a rigid pointed head which at first is turned upwards, and as their ends are close together, constitute a sort of spike. At first, I say, the flower-heads point upwards like those of other clovers, but as soon as the florets are fertilised, the flower-stalks bend over and grow- downwards, forcing the flower-head into the ground, an operation much facilitated by the peculiar con- struction and arrangement of the imperfect florets. The florets are, as Darwin has shown, no mere passive instruments. So soon as the flower-head is in the ground they begin, commencing from the outside, to bend themselves towards the peduncle, the result of which of course is to drag the flower- head further and further into the ground. In most clovers each floret produces a little pod. This would in the present species be useless ; many young plants growing in one place would jostle and starve one another. Hence we see another obvious advantage in the fact that only a few florets perfect their seeds. 2. I have already alluded to our Cardamines, the pods of which open elastically and throw their seeds some distance. A Brazilian species (fig. 81), besides the usual long pods (fig. 81, a a), produces Fruits and Seeds. 21 1 also short pointed ones (fig. 8i,& #), which it buries in the ground. In the case of the Ground-nut of the West Indies the flower is yellow and resembles that of a pea, but has an elongated calyx, at the base of which, and close to the stem, is the ovary. After the flower has faded, the young pod, which is oval, pointed, and very minute, is carried forward by the growth of the stalk, which becomes two or three inches long and curves downwards so as generally to force the pod into the ground. If it fails in this, the pod does not develop, but soon perishes ; on the other hand, as soon as it is underground the pod begins to grow and develops two large seeds. 3. In a South European species of Vetch (fig. 82) there are two kinds of pods. One of the ordinary form and habit (a), the other (£), oval, pale, con- taining only two seeds borne on underground stems, and produced by flowers which have no corolla. Again, a species of the allied genus Lathyriis (fig. 83) affords us another case of the same pheno- menon. There are many other species possessing the same faculty of burying their seeds, belonging moreover to very different families of plants. 4. Moreover, it is interesting that in several of these the subterranean pods differ from the usual and aerial form in being shorter and containing fewer seeds. The reason of this is, I think, obvious. In the ordinary pods the number of seeds of course P 2 2 1 2 Fruits and Seeds. increases the chance that some will find a suitable place. On the other hand, the subterranean ones Fig. 82. — VETCH (Vicia amphicarpa\ a a, ordinary pods ; b 6, subterranean pods. are carefully sown, as it were, by the plant itself. Several seeds together would only interfere with Fruits and Seeds. 213 one another, and it is therefore better that one or two only should be produced. ig- 83. — PEA (Lathyrus aniphicarpos). , ordinary pods ; b, subterranean pods. 5. In the Crane's Bills the fruit is a capsule which opens elastically, in some species throwing the 214 Fruits and Seeds, seeds to some little distance. The seeds them- selves are more or less spindle-shaped, hairy, and produced into a twisted hairy awn, as shown in fig. 84. The number of spiral turns in the awn depends upon the amount of moisture ; and the seed may Fig. 84. — Seed of CRANE'S BILL. thus be made into a very delicate hygrometer, for if it be fixed in an upright position, the awn twists or untwists according to the degree of moisture, and its extremity thus may be so arranged as to move up and down like a needle on a register. It is also affected by heat. Now, if the awn were Fruits and Seeds. 2 1 5 fixed, it is obvious that during the process of untwisting the seed itself would be pressed down- wards, and this mechanism thus serves actually to bury the seed. 6. If a seed of this plant is laid on the ground, it remains quiet as long as it is dry ; but as soon as it is moistened — i.e., as soon as the earth be- comes in a condition to permit growth — the outer side of the awn contracts, and the hairs surround- ing the seed commence to move outwards, the result of which is gradually to raise the seed into an upright position with its point on the soil. The awn then commences to unroll, and consequently to lengthen itself upwards, and it is obvious that as it is covered with reversed hairs, it will probably press against some blade of grass or other obstacle, which will prevent its moving up, and will there- fore tend to drive the seed into the ground. If then the air becomes dryer, the awn will again roll up, when from the position of the hairs the feathery awn can easily slip downwards, and will therefore not affect the seed. When moistened once more, it will again force the seed further downwards, and so on until the proper depth is obtained. One of the Mountain Anemones again has essentially the same arrangement, though belonging to a widely separated order. 7. A still more remarkable instance is afforded by a beautiful South European grass, Stipa pennata - 85). The actual seed is small, with a sharp Fig. 85. — Seed of STIPA, a South European Grass. (Natural size.) Fruits and Seeds. 217 point, and stiff, short hairs pointing backwards. The posterior end of the seed is produced into a fine twisted corkscrew-like rod, which is followed by a plain cylindrical portion, attached at an angle to the corkscrew, and ending in a long and beautiful feather, the whole being more than a foot in length. The long feather, no doubt, facilitates the disper- sion of the seeds by wind ; eventually, however, the seeds sink to the ground, which they tend to reach (the feather being the lighter portion), point down- wards. Frank Darwin considers that the seed re- mains in that position as long as it is dry, but if a shower comes on, or when the dew falls, the spiral unwinds, and if, as is most probable, the surround- ing herbage or any other obstacle prevents the feathers from rising, the seed itself is forced down and so driven by degrees into the earth. I have suggested, on the contrary, that the wind acting on the feather gradually drives the seeds into the ground. 218 Fruits and Seeds. VII. I. I have already mentioned several cases in which plants produce two kinds of seeds, or at least of pods, the one being adapted to burying itself in the ground. There is, in addition, a North African species of Corydalis which produces two kinds of seeds (fig. 86), one somewhat flattened, short and NatfSize Fig. 86. — Seeds of CORYDALIS. broad, with rounded angles ; the other elongated, and hooked. In this case the hook in the latter form perhaps serves for dispersion. 2. Our common Lesser Hawkbit (fig. 76, b} also possesses, besides the fruits with the well-known feathery crown, others which are destitute of such Fruits and Seeds. 219 a provision, and which probably therefore are intended to take root at home. Mr. Drummond has described a species of Alis- macece which has two sorts of seed-vessels ; the one produced from large floating flowers, the other at the end of short submerged stalks. He does not, however, describe either the seeds or seed-vessels in detail. 3. Before concluding I will say a few words as to the very curious forms presented by certain seeds and fruits. The pods of Lotus, for instance, quaintly resemble a bird's foot, even to the toes ; whence the specific name of one species, ornithopodioides, which means " like a bird's foot " ; those of Hippocrepis re- mind one of a horseshoe ; those of Trapa bicornis have an absurd resemblance to the skeleton of a bull's head. These likenesses appear to be acci- dental, but there are some which probably are of use to the plant. For instance, there are two species of Scorpiurus (fig. 87) , the pods of which lie on the ground, and so curiously resemble, the one (fig. 87, a) a centipede, the other (fig. 87, &) a worm or cater- pillar, that it is almost impossible not to suppose that the likeness must be of some use to the plant. The pod of a kind of Biserrula (fig. 88) also has a striking resemblance to a flattened centipede ; while the seeds of Abrus, both in size and in their very striking colour, mimic a small beetle, Artemis circumusta. 4. Mr. Moore has recently called attention to other 220 Fruits and Seeds. Fig. 87. a, pod of Scorpiurus subvillosa; b, pod of Scorpiurus vermicidata. Fruits and Seeds. 22 1 cases of this kind. Thus the seed of Martynia diandra much resembles a beetle with long an- tennae ; several species of Lupins have seeds much like spiders, and those of a gourdlike plant,* mimic a piece of dry twig. In the common castor oil plants (fig. 89), though the resemblance is not so Fig. 88.— Pod of BISERRULA. Fig. 89. — Seed of CASTOR OIL PLANT. close, still at a first glance the seeds might readily be taken for beetles or ticks. In many plants allied to Euphorbia plants, as, for instance, in Jatropha (fig. 90), the resemblance is even more striking. The seeds have a central line resembling the space between the elytra, or wing cases, dividing and * Dimorphochlamys. 222 Fruits and Seeds. slightly diverging at the end, while between them the end of the abdomen seems to peep ; at the anterior end the seeds possess a small lobe, which mimics the head or thorax of the insect, and which even seems specially arranged for this purpose ; at least it would seem from experiments made at Kew that the removal of this little lobe does not injure the seed. 5. These resemblances might benefit the plant in one of two ways. If it be an advantage to the plant that the seeds should be swallowed by birds, Fig. 90. — Seed of JATROPHA. their resemblance to insects might lead to this result. On the other hand, if it be desirable to escape from grain-eating birds, then the resem- blance to insects would serve as a protection. We do not, however, yet know enough about the habits of these plants to solve this question. 6. Indeed, as we have gone on, many other ques- tions will, I doubt not, have occurred to you, which we are not yet in a position to answer. Seeds, for instance, differ almost infinitely in the sculpturing Fruits and Seeds. 223 of their surface. I shall have failed woefully in my object if I leave you with the impression that we know all about seeds. On the contrary, there is not a fruit or a seed, even of one of our com- monest plants, which would not amply justify and richly reward the most careful study. 7. In this, as in other branches of science, we have but made a beginning. We have learnt just enough to perceive how little we know. 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