Fig. 8.—Pitcher of Sarracenia purpurea, reduced, with section.
There is a characteristic figure of this Sarracenia in old Gerarde's "Herbal" (1597), where it is called "hollow-leaved sea-lavender," and stated to be copied from Clusius, "for the strangenesse thereof, but hope that some or other that travell into forraine parts may finde this elegant plant, and know it by this small expression, and bring it home with them, that so we may come to a perfecter knowledge thereof."—P. 412.
As to the fluids, we must carefully guard against misinterpretation. To this end it must be borne in mind that the honey-like, or saccharine, exudation from the lip of the tube, and the fluid, contained in greater or less quantity at the bottom of the tube, are two quite different and distinct substances. The latter will receive attention hereafter, but our present subject is the secretion which is found as a bait or lure at the mouth of the tube. This, combined with the bright colouring, may be fairly assumed to have been provided for some special purpose. Dr. McBride calls it the "cause which attracts flies," and Dr. Mellichamp, of South Carolina, set himself to investigate this, and some other disputed points, upon living plants. Having discovered some advanced plants of Sarracenia, he had no difficulty in detecting, in almost every leaf, the sugary secretion or honey-like exudation, noticed by Dr. McBride, and other observers, as being found at the mouth of the tube. "I found it," he writes, "precisely in the place described, save that it extended downwards more than a quarter of an inch, generally half an inch, or even three quarters of an inch. I also found it more sparingly under the arched lid, or upper lip of the leaf, in and among the thick and coarse hairs found there, and which, I believe, are thicker and coarser than those in the lowermost portion of the tube. Dr. McBride, however, failed to trace the continuance of the sugary exudation, which I frequently found glistening, and somewhat viscid, along the whole red or purple-coloured border, or edging of the broad wing, extending from the cleft in the lower lip, even to the ground. There is, therefore, a painted or honey-baited pathway, leading directly from the petiole (or the ground itself) up to the mouth, where it extends on each side, as far as the commissures of the lips, from which it runs within, and downwards, for at least half an inch."
<!-- image -->Fig. 9.—Hairs from mouth of Sarracenia, magnified.
"One can now readily understand why ants should so frequently be found among the earliest macerated insects at the base of the tube. Their fondness for saccharine juices is well known, and, while reconnoitring at the base of the leaf, and bent on plunder, they are doubtless soon attracted by the sweets of the honeyed path lying right before them, along which they may eat as they march, until the mouth is reached, where certain destruction awaits them."
In order to determine the character of the saccharine exudation, and whether it possessed any intoxicating properties, Dr. Mellichamp collected a large number of mature, and most sugary, leaves, which he placed in vessels of water on reaching home, and sat down before them for two hours watching the result. Flies were soon attracted to the leaves, but by no means greedily, and many were entrapped, the buzzing of unfortunate prisoners being incessant. Finding that he could not see the process with the lids in their normal position, he turned backwards the greater part of the overhanging lid, and let daylight into the prison, so that the whole region of the sugar countries could be seen, and examined, while the flies were busy at their food.
"After turning back the lids of most of the leaves," he says, "the flies would enter as before, a few alighting on the honeyed border of the wing, and walking upward—sipping as they went—to the mouth, and entering at the cleft of the lower lip; others would alight on the top of the lid and then walk under the roof, feeding there; but most, it seemed to me, preferred to alight just at the commissure of the lips, and either enter the tube immediately there, feeding downward upon the honey pastures, or would linger at the trunk, sipping along the whole edge of the lower lip and eventually enter near the cleft. After entering (which they generally do with great caution and circumspection) they begin again to feed, but their foothold, for some reason or other, seems unsecure, and they occasionally slip, as it appears to me, upon this exquisitely soft and velvety declining pubescence. The nectar is not exuded or smeared over the whole of this surface, but seems disposed in separate little drops. I have seen them regain their foothold after slipping, and continue to sip, but always moving slowly and with apparent caution, as if aware that they are treading on dangerous ground. After sipping their fill they frequently remain motionless, as if satiated with delight, and, in the usual self-congratulatory manner of flies, proceed to rub their legs together, but in reality, I suppose, to cleanse them. It is then they betake themselves to flight, strike themselves against the opposite sides of the prison-house, either upward or downward, generally the former. Obtaining no perch or foothold, they rebound off from this velvety microscopic chevaux-de-frise, which lines the inner surface still lower, until, by a series of zigzag but generally downward falling flights, they finally reach the coarser and more bristly pubescence of the lower chamber, where, entangled somewhat, they struggle frantically (but by no means drunk or stupefied), and eventually slide into the pool of death, where, once becoming slimed and saturated with these Lethean waters, they cease from their labours. And even here, although they may cease to struggle, and seem dead, like 'drowned flies,' yet are they only asphyxiated, not by the nectar but by this 'cool and animating fluid, limpid as the morning dew.' After continued asphyxia they die, and after maceration they add to the vigour and sustenance of the plant. And this seems to be the true use of the 'limpid fluid,' for it does not seem to be at all necessary to the killing of the insects (although it does possess that power), the conformation of the funnel of the fly-trap is sufficient to destroy them. They only die the sooner, and the sooner become 'liquid manure.'
"I could never see any indication of unsteadiness or tottering in the sipping flies—nothing save an occasional slip from the uncertain hold which the peculiar pubescence would give, save once or twice while watching intently I saw a fly disappear so quickly downwards that I could not with certainty say whether it was flight or a tumble from stupor or insensibility. But on so many other occasions have I satisfied myself to the contrary, by seeing them fly upward as well as downward, with full vigour of an unhurt unintoxicated insect, that I altogether reject the idea of stupor. I may state that while watching I observed not a single escape when the lid was down, but after I had turned it back on most of the leaves under examination, a few, but only a few, escaped. And those which escaped, after sipping to repletion, seemed in no wise inebriated."
Pursuing these investigations still further, on another occasion he collected the laminæ of about one hundred leaves, all sweet with the exudation. Some of these were placed on a table, after candlelight, and attracted a few hungry flies. They remained many minutes sipping, and would return to sip, seeming to enjoy the evening meal thus afforded them. Of course there could be no entrapment, as only the honey-bearing portions were exposed. The flies ate, and ate, but no unsteadiness, or tottering, or falling, was in a single instance to be seen; and, after having satisfied their appetites, the guests retired for the night. The following day the same tempting viands were placed before the flies, but there was no evidence of a single case of intoxication.
If true that the exudation possessed no intoxicating property, sceptics were next led to inquire how it was that insects were entrapped whilst still in possession of all their instincts and faculties unimpaired; and to answer this the same careful observer narrated his experience as to how the flies are entrapped. "The nectar being found below the lower lip for half an inch or more, when the fly is satiated, and makes for flight, he must do so immediately upward for a very short distance, and then somewhat at right angles, to get through the outlet—a rather difficult flight, which perhaps of all insects only a fly might be capable of, but which even he probably is not. This, too, upon the supposition that his head is upward, whereas his head is, I believe, generally downward, or at least parallel with the lip. If in the first position he attempts flight, he is very apt to strike the arch overhead, and, if he escapes that, it is next to an impossibility for him to turn and strike that small space between the projecting (and downward projecting) lid and the lower lip. If with head downward, he is very apt in flight to strike the opposite wall at a still lower angle, and then, from rebound to rebound, get lower and lower until he touches the pool. In almost every instance, therefore, a fly once entering is caught."
The next point for inquiry refers to the fluid contained at the bottom of the tubes or pitchers. What is this fluid which is almost universally present, and what its purpose? Dr. Mellichamp says:—"The first point to decide seemed to be whether the watery fluid found in the leaves was a true secretion of the plant or only rain-water. As I have two or three patches of Sarracenia conveniently near in a neighbouring pine barren, it was no difficult matter to make the necessary examinations. On the 22nd, therefore, the sandy pine-land being very dry and thirsty—no rain having fallen for some days—I visited the plants, which were blooming freely. Many leaves were carefully examined with the throat still closed and impervious to water, and inflated, as they usually are, with air. Upon slight pressure the air would escape, thus opening the throat for inspection. The leaf being tilted, there was almost invariably an escape of fluid—from three to five drops generally—occasionally as many as ten drops, and rarely fifteen drops. It is, therefore, a true secretion, as no rain could possibly have been admitted to the completely-closed and sealed leaf.
"The taste of this secretion was bland, and somewhat mucilaginous, yet seemingly leaving in the mouth a peculiar astringency, recalling very accurately the taste of the root, with which I was quite familiar. So much for the examination of the not yet matured and unopened leaves, in which I may as well remark that I could find no trace of insects, either by puncture, or eggs, or larvæ, nor indeed any débris of any kind.
"I next examined a great many perfect leaves with the throat open. In almost every leaf the secretion was to be found, containing generally from ten to fifteen drops, very rarely a half drachm. Even in these open leaves the admission of rain-water is next to impossible, so completely does the upper lid overhang the mouth or throat, like the projecting eaves of a house. Unless in a severe rain-storm, and perhaps not even then, would this be possible.
"With very rare exceptions dead and decaying, or, more properly, macerated insects were to be found packed at the base of the tube—most frequently a large red ant—also beetles, bugs, flies, &c., and invariably within the decaying mass one or more small white worms, perhaps the larvæ of insects hatched within the putrefying mass."