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PROFESSOR ASA GRAY, the eminent botanist, was born in Paris, Oneida County, New York, November 18, 1810. He studied medicine, but his enthusiastic love of botanical investigation withheld him from the practice of his profession. In 1834 he received the appointment of Botanist to the United States Exploring Expedition, but, impatient of the delays which hindered that enterprise, he resigned his office in 1837. About that time he was chosen Professor of Botany in the University of Michigan; before that institution was opened he accepted the Fisher Professorship of Natural History in Harvard University, and has ever since filled it with honor to himself and great advantage to science. His first contribution to the literature of botany was North American Graminee and Cyperaceae, of which two volumes were published in 1834-35. This brought him prominently before the scientific world. His botanical career, however, may be said to date from his reading in December, 1834, before the New York Lyceum of Natural History, of A Notice of some New, Rare, or otherwise Interesting Plants from the Northern and Western Portions of the State of New York. In 1838, in conjunction with John Torrey, M. D., he prepared the first part of The Flora of North America. This work has never been completed; but in its fragmentary state it is esteemed one of the most valuable contributions ever made in America to the science of Botany. The collections made by the Exploring Expedition of Commodore Wilkes, during the years 1838-42, except those obtained from the Pacific Coast, were placed in the hands of Professor Gray for elaboration, and the fruits of his labors are preserved in two volumes on the Botany of the United States Exploring Expedition. His numerous papers in the memoirs of the learned societies, although not of a popular character, comprise a large part of his most important contributions to science. The most generally interesting one is his Memoir on the Botany of Japan in its Relations to that of the United States, which subject was followed up in his Address as President of the American Association for the Advancement of Science, delivered at Dubuque, August, 1872. But while, by the works above-mentioned and many others unnamed, Professor Gray has won fame at home and abroad, he has established a still stronger claim upon the grateful respect of humanity by his untiring and successful efforts to popularize the study of Botany by means of elementary books. His Structural Botany has gone through a multitude of editions, and is universally accepted as one of the best expositions of vegetable physiology and morphology ever written, while his Manual of Botany has long been known as a standard work. Within a few years he has produced several books of an elementary character, which combine literary grace and substantial instruction in singularly happy union. Among these are How Plants Grow, How Plants Behave, Lessons in Botany, The School and Field Book of Botany, etc. Professor Gray possesses remarkable qualifications for this work, his expositions being singularly clear, and his style in all respects attractive. As a representative of science in America, he enjoys an enviable reputation abroad, and his works are quoted with admiring respect by the most distinguished European savans.
HOW CERTAIN PLANTS CAPTURE INSECTS.
THIS is not a common habit of plants. Insects are fed and allowed to depart unharmed. When captures are made they must sometimes be purely accidental and meaningless; as in those species of Silene called Catch-fly, because small flies and other weak insects, sticking fast to a clammy exudation of the calyxes in some species, of a part of the stem in others, are unable to extricate themselves and so perish. But in certain cases insects are caught in ways so remarkable that we cannot avoid regarding them as contrivances, as genuine fly-traps.
Flower fly-traps are certainly to be found in some plants of the Orchis family. One instance is that of Cypripedium or Lady'sSlipper, which is a contrivance for cross-fertilization. Here the insect is entrapped for the purpose of securing its services; and the detention is only temporary. If it did not escape from one flower to enter into another, the whole purpose of the contrivance would be defeated. Not so, however, in leaf fly-traps. These all take the insect's life, whether with intent or not it may be difficult to make out. The commonest and the most ambiguous leaf fly-traps are such as Pitchers, of which those of our Sarracenia or Sidesaddle-flower are most familiar. A common yellow-flowered species of the Southern States has them so very long and narrow, that they are popularly named Trumpets. In these pitchers or tubes water is generally found, sometimes caught from rain, but in other cases evidently furnished by the plant, the pitcher being so constructed that water cannot rain in : this water abounds with drowned insects, commonly in all stages of decay. One would suppose that insects which have crawled into the pitcher might as readily crawl out; but they do not, and closer examination shows that escaping is not as easy as entering. In most pitchers of this sort there are sharp and stiff hairs within, all pointing downward, which offer considerable obstruction to returning, but none to entering.
Why plants which are rooted in wet bogs or in moist ground need to catch water in pitchers, or to secrete it there, is a mystery, unless it is wanted to drown flies in. And what they gain from a solution of dead flies is equally hard to guess, unless this acts as a liquid manure.
Into such pitchers as those of the common species rain may fall; but not readily into others, not at all into those of the Parrot-headed species of the Southern States, for the inflated lid or cover arches over the mouth of the pitcher completely. This is even more strikingly so in Darlingtonia, the curious Californian Pitcher-plant lately made known and cultivated in this the contracted entrance to the pitcher is concealed under the hood and looks downward instead of upward; and even the small chance of any rain entering by aid of the wind is, as it were, guarded against by a curious appendage, resembling the forked tail of some fish, which hangs over the front. Any water found in this pitcher must come from the plant itself. So it also must in the combined Pitcher and Tendril of Nepenthes. These Pitcher-plants are woody climbers, natives of the Indian Archipelago,
and not rarely cultivated in hothouses, as a curiosity. Some of their leaves lengthen the tip into the tendril only; some of the lower bear a pitcher only; but the best developed leaves have both, — the tendril for climbing, the pitcher one can hardly say for what purpose. The pitcher is tightly closed by a neatly fitting lid when young; and in strong and healthy plants there is commonly a little water in it, which could not possibly have been introduced from without. After they are fully grown the lid opens by a hinge; then a little water might be supposed to rain in. In the humid, sultry climates they inhabit it probably does so freely; and the leaves are found partly filled with dead flies, as in our wild Pitcher-plants.
The drowning of insects in plant-pitchers is of course an accidental occurrence, and any supposed advantage of this to the plant may be altogether fanciful. But we cannot deny that the supply of liquid manure may be useful. Before concluding that they are of no account, it may be well to contemplate other sorts of leaf fly-traps.
All species of Sundew (Drosera) have their leaves, and some their stalks also, beset with bristles tipped with a gland from which oozes a drop of clear but very glutinous liquid, making the plant appear as if studded with dew-drops. These remain, glistening in the sun, long after dew-drops would have been dissipated. Small flies, gnats, and such-like insects, seemingly enticed by the glittering drops, stick fast upon them, and perish by starvation, one would suppose without any benefit whatever to the plant. But in the broad-leaved wild species of our bogs, such as the common Round-leaved Sundew, the upper face and edges of the blade of the leaf bear stronger bristles, tipped with a larger glutinous drop, and the whole forms what we must allow to be a veritable fly-trap.
For, when a small fly alights on the upper face, and is held by some of the glutinous drops long enough for the leaf to act, the surrounding bristles slowly bend inwards so as to bring their glutinous tips also against the body of the insect, adding, one by one, to the bonds, and rendering captivity and death certain. This movement of the bristles must be of the same nature as that by which tendrils and some leafstalks bend or coil. It is much too slow to be visible except in the result, which takes a few hours or even a day or two to be completed. Here, then, is a contrivance for catching flies, a most elaborate one, in action slow but sure. And the different species of Sundew offer all gradations between those with merely scattered and
motionless dewy-tipped bristles, to which flies may chance to stick, and this more complex arrangement, which we cannot avoid regarding as intended for fly-catching. Moreover, in both of our commoner species, the blade of the leaf itself incurves, so as to fold round its victim!
And a most practiced observer, whose observations are not yet published, declares that the leaves of the common Round-leaved Sundew act differently when different objects are placed upon them. For instance, if a particle of raw meat be substituted for the living fly, the bristles will close upon it in the same manner; but to a particle of chalk or wood they remain nearly indifferent. If any doubt should still remain whether the fly-catching in Sundews is accidental or intentional, in other words, whether the leaf is so constructed and arranged in order that it may capture flies, the doubt may perhaps disappear upon the contemplation of another and even more extraordinary plant of the same family of the Sundew, namely, Venus's Flytrap, or Dionea muscipula. This plant abounds in the low savannas around Wilmington, North Carolina, and is native nowhere else. It is not very difficult to cultivate, at least for a time, and it is kept in many choice conservatories as a vegetable wonder.
The trap is the end of the leaf. It is somewhat like the leaf of Sundew, only larger, about an inch in diameter, with bristles still stouter, but only round the margin, like a fringe, and no clammy liquid or gland at their tips. The leaf folds on itself as if hinged at the midrib. Three more delicate bristles are seen on the face upon close inspection. When these are touched by the finger or the point of a pencil, the open trap shuts with a quick motion, and after a considerable interval it reopens. When a fly or other insect alights on the surface and brushes against these sensitive bristles, the trap closes promptly, generally imprisoning the intruder. It closes at first with the sides convex and the bristles crossing each other like the fingers of interlocked hands or the teeth of a steel trap. But soon the sides of the trap flatten down and press firmly upon the victim; and it now requires a very considerable force to open the trap. If nothing is caught, the trap presently reopens of itself and is ready for another attempt. When a fly or any similar insect is captured it is retained until it perishes, is killed, indeed, and consumed; after which it opens for another capture. But after the first or second it acts sluggishly and feebly, it ages and hardens, at length loses its sensibility, and slowly decays.
It cannot be supposed that plants, like boys, catch flies for pastime or in objectless wantonness. Living beings though they are, yet they are not of a sufficiently high order for that. It is equally incredible that such an exquisite apparatus as this should be purposeless. And in the present case the evidence of the purpose and of the meaning of the strange action is wellnigh complete. The face of this living trap is thickly sprinkled with glands immersed in its texture, of elaborate structure under the microscope, but large enough to be clearly discerned with a hand-lens; these glands, soon after an insect is closed upon, give out a saliva-like liquid, which moistens the insect, and in a short time (within a week) dissolves all its soft parts, digests them, we must believe; and the liquid, with the animal matter it has dissolved, is re-absorbed into the leaf! We are forced to conclude that, in addition to the ordinary faculties and function of a vegetable, this plant is really carnivorous.
That, while all plants are food for animals, some few should, in turn and to some extent, feed upon them, will appear more credible when it is considered that whole tribes of plants of the lowest grade (Mould-Fungi and the like) habitually feed upon living plants and living animals, or upon their juices when dead. An account of them would make a volume of itself, and an interesting one. But all goes
to show that the instances of extraordinary behavior which have been recounted in these chapters are not mere prodigies, wholly out of the general order of Nature, but belong to the order of Nature, and indeed are hardly different in kind from, or really more wonderful than, the doings of many of the commonest plants, which, until our special attention is called to them, ordinarily pass unregarded.
*How Plants Behave: How they move, climb, employ insects to work for them, etc. A charming elementary work, from which this extract is taken.