Insectivorous Plants (Darwin)

From Wikisource
Jump to: navigation, search






Authorised Edition.


In the present Edition I have not attempted to give a complete account of the progress of the subject since 1875. Nor have I called attention to those passages occurring occasionally throughout the book wherein the Author makes use of explanations, illustrations, or reference to authorities which seems to me not perfectly satisfactory. I have merely wished to indicate the more important points brought to light by recent research. The additions are in some cases placed in the text, but they are more commonly given as footnotes. They are, in all cases, indicated by means of square brackets.

Misprints, errors in numbers, &c., have been set right, and a few verbal corrections have been taken from Charles Darwin's copy of the First Edition. Otherwise the text remains unchanged.

Cambridge, July, 1888.


Drosera rotundifolia, or the Common Sun-dew.

Number of insects captured—Description of the leaves and their appendages or tentacles—Preliminary sketch of the action of the various parts, and of the manner in which insects are captured—Duration of the inflection of the tentacles—Nature of the secretion—Manner in which insects are carried to the centre of the leaf—Evidence that the glands have the power of absorption—Small size of the roots

Pages 1–17

The Movements of the Tentacles from the Contact of Solid Bones.

Inflection of the exterior tentacles owing to the glands of the disc being excited by repeated touches, or by objects left in contact with them—Difference in the action of bodies yielding and not yielding soluble nitrogenous matter—Inflection of the exterior tentacles directly caused by objects left in contact with their glands—Periods of commencing inflection and of subsequent re-expansion—Extreme minuteness of the particles causing inflection—Action under water—Inflection of the exterior tentacles when their glands are excited by repeated touches—Falling drops of water do not cause inflection


Aggregation of the Protoplasm within the Cells of the Tentacles.

Nature of the contents of the cells before aggregation—Various causes which excite aggregation—The process commences within the glands and travels down the tentacles—Description of the aggregated masses and of their spontaneous movements—Currents of protoplasm along the walls of the cells—Action of carbonate of ammonia—The granules in the protoplasm which flows along the walls coalesce with the central masses—Minuteness of the quantity of carbonate of ammonia causing aggregation—Action of other salts of ammonia—Of other substances, organic fluids, &c.—Of water—Of heat—Redissolution of the aggregated masses—Proximate causes of the aggregation of the protoplasm—Summary and concluding remarks—Supplementary observations on aggregation in the roots of plants

Pages 33–55

The Effects of Heat on the Leaves.

Nature of the experiments—Effects of boiling water—Warm water causes rapid inflection—Water at a higher temperature does not cause immediate inflection, but does not kill the leaves, as shown by their subsequent re-expansion and by the aggregation of the protoplasm—A still higher temperature kills the leaves and coagulates the albuminous contents of the glands


The Effects of Non-nitrogenous and Nitrogenous Organic Fluids on the Leaves.

Non-nitrogenous fluids—Solutions of gum arabic—Sugar—Starch—Diluted alcohol—Olive oil—Infusion and decoction of tea—Nitrogenous fluids—Milk—Urine—Liquid albumen—Infusion of raw meat—Impure mucus—Saliva—Solution of isinglass—Difference in the action of these two sets of fluids—Decoction of green peas—Decoction and infusion of cabbage—Decoction of grass leaves


The Digestive Power of the Secretion of Drosera.

The secretion rendered acid by the direct and indirect excitement of the glands—Nature of the acid—Digestible substances—Albumen, its digestion arrested by alkalies, recommences by the addition of an acid—Meat—Fibrin—Syntonin—Areolar tissue—Cartilage—Fibro—cartilage—Bone—Enamel and dentine—Phosphate of lime—Fibrous basis of bone—Gelatine—Chondrin—Milk, casein and cheese—Gluten—Legumin—Pollen—Globulin—Haematin—Indigestible substances—Epidermic productions—Fibro—elastic tissue—Mucin—Pepsin—Urea—Chitine—Cellulose—Gun-cotton—Chlorophyll—Fat and oil—Starch—Action of the secretion on living seeds—Summary and concluding remarks


The Effects of Salts of Ammonia.

Manner of performing the experiments—Action of distilled water in comparison with the solutions—Carbonate of ammonia, absorbed by the roots—The vapour absorbed by the glands—Drops on the disc—Minute drops applied to separate glands—Leaves immersed in weak solutions—Minuteness of the doses which induce aggregation of the protoplasm—Nitrate of ammonia, analogous experiments with—Phosphate of ammonia, analogous experiments with—Other salts of ammonia—Summary and concluding remarks on the action of salts of ammonia


The Effects of various other Salts, and Acids, on the Leaves.

Salts of sodium, potassium, and other alkaline, earthy, and metallic salts—Summary on the action of these salts—Various acids—Summary on their action


The Effects of certain Alkaloid Poisons, other Substances and Vapours.

Strychnine, salts of—Quinine, sulphate of, does not soon arrest the movement of the protoplasm—Other salts of quinine—Digitaline—Nicotine—Atropine—Veratrine—Colchicine—Theine—Curare—Morphia—Hyoscyamus—Poison of the cobra, apparently accelerates the movements of the protoplasm—Camphor, a powerful stimulant, its vapour narcotic—Certain essential oils excite movement—Glycerine—Water and certain solutions retard or prevent the subsequent action of phosphate of ammonia—Alcohol innocuous, its vapour narcotic and poisonous—Chloroform, sulphuric and nitric ether, their stimulant, poisonous, and narcotic power—Carbonic acid narcotic, not quickly poisonous—Concluding remarks


On the Sensitiveness of the Leaves, and on the Lines of Transmission of the Motor Impulse.

Glands and summits of the tentacles alone sensitive—Transmission of the motor impulse down the pedicels of the tentacles, and across the blade of the leaf—Aggregation of the protoplasm, a reflex action—First discharge of the motor impulse sudden—Direction of the movements of the tentacles—Motor impulse transmitted through the cellular tissue—Mechanism of the movements—Nature of the motor impulse—Re-expansion of the tentacles


Recapitulation of the Chief Observations on Drosera rontundifolia.


On the Structure and Movements of some other Species of Drosera.

Drosera anglicaDrosera intermediaDrosera capensisDrosera spathulataDrosera filiformisDrosera binata—Concluding remarks

Pages 226–231

Dionæa muscipula.

Structure of the leaves—Sensitiveness of the filaments—Rapid movement of the lobes caused by irritation of the filaments—Glands, their power of secretion—Slow movement caused by the absorption of animal matter—Evidence of absorption from the aggregated condition of the glands—Digestive power of the secretion—Action of chloroform, ether, and hydrocyanic acid—The manner in which insects are captured—Use of the marginal spikes—Kinds of insects captured—The transmission of the motor impulse and mechanism of the movements—Re-expansion of the lobes


Aldrovanda vesiculosa.

Captures crustaceans—Structure of the leaves in comparison with those of Dionæa—Absorption by the glands, by the quadrifid processes, and points on the infolded margins—Aldrovanda vesiculosa, var. australis—Captures prey—Absorption of animal matter—Aldrovanda vesiculosa, var. verticillata—Concluding remarks


Drosophyllum —Roridula —Byblis —Glandular Hairs of other Plants —Concluding Remarks of the Droseraceæ.

Drosophyllum—Structure of leaves—Nature of the secretion—Manner of catching insects—Power of absorption—Digestion of animal substances—Summary on Drosophyllum—Roridula—Byblis—Glandular hairs of other plants, their power of absorption—Saxifraga—Primula—Pelargonium—Erica—Mirabilis—Nicotiana—Summary on glandular hairs—Concluding remarks on the Droseraceæ



Pinguicula vulgaris—Structure of leaves—Number of insects and other objects caught—Movement of the margins of the leaves—Uses of this movement—Secretion, digestion, and absorption—Action of the secretion on various animal and vegetable substances—The effects of substances not containing soluble nitrogenous matter on the glands—Pinguicula grandifloraPinguicula lusitanica, catches insects—Movement of the leaves, secretion and digestion

Pages 298–319


Utricularia neglecta—Structure of the bladder—The uses of the several parts—Number of imprisoned animals—Manner of capture—The bladders cannot digest animal matter, but absorb the products of its decay—Experiments on the absorption of certain fluids by the quadrifid processes—Absorption by the glands—Summary of the observation on absorption—Development of the bladders—Utricularia vulgarisUtricularia minorUtricularia clandestina


Utricularia (continued).

Utricularia montana—Description of the bladders on the subterranean rhizomes—Prey captured by the bladders of plants under culture and in a state of nature—Absorption by the quadrifid processes and glands—Tubers serving as reservoirs for water—Various other species of Utricularia—Polypompholyx—Genlisea, different nature of the trap for capturing prey—[Sarracenia]—Diversified methods by which plants are nourished