Part 8 (1/2)

There are six native species of the cypripedium in this Eastern region, varying in shape and in color--shades of white, yellow, crimson, and pink. The mechanism of their cross-fertilization is the same in all, with only slight modifications.

The most common of the group, the _C. acaule_, most widely known as the moccasin-flower, whose large, nodding, pale crimson blooms we so irresistibly a.s.sociate with the cool hemlock woods, will afford a good ill.u.s.tration.

The lip in all the cypripediums is more or less sac-like and inflated.

In the present species, _C. acaule_, however, we see a unique variation, this portion of the flower being conspicuously bag-like, and cleft by a fissure down its entire anterior face. In Fig. 16 is shown a front view of the blossom, showing this fissure. The ”column” (B) in the cypripedium is very distinctive, and from the front view is very non-committal. It is only as we see it in side section, or from beneath, that we fully comprehend the disposition of stigma and pollen. Upon the stalk of this column there appear from the front three lobes--two small ones at the sides, each of which hides an anther attached to its under face--the large terminal third lobe being in truth a barren rudiment of a former stamen, and which now overarches the stigma. The relative position of these parts may be seen in the under view.

[Ill.u.s.tration]

The anthers in this genus, then, are two, instead of the previous single anther with its two pollen-cells. The pollen is also quite different in its character, being here in the form of a pasty ma.s.s, whose entire exposed surface, as the anther opens, is coated with a very viscid gluten.

[Ill.u.s.tration: Fig. 16]

With the several figures ill.u.s.trating the cross-fertilization, the reader will readily antic.i.p.ate any description of the process, and only a brief commentary will be required in my text.

I have repeatedly examined the flowers of _C. acaule_ in their haunts, have observed groups wherein every flower still retained its pollen, others where one or both pollen ma.s.ses had been withdrawn, and in several instances a.s.sociated with them I have observed the inflated lip most outrageously bruised, torn, and battered, and occasionally perforated by a large hole. I had observed these facts in boyhood. The inference, of course, was that some insect had been guilty of the mutilation; but not until I read Darwin's description of the cross-fertilization of this species did I realize the full significance of these telltale evidences of the escape of the imprisoned insect.

Since that time, many years ago, I have often sat long and patiently in the haunt of the cypripedium awaiting a natural demonstration of its cross-fertilization, but as yet no insect has rewarded my devotion.

[Ill.u.s.tration: Fig. 17]

At length, in hopelessness of reward by such means, I determined to see the process by more prosaic methods. Gathering a cl.u.s.ter of the freshly opened flowers, which still retained their pollen, I took them to my studio. I then captured a b.u.mblebee, and forcibly persuaded him to enact the demonstration which I had so long waited for him peaceably to fulfil. Taking him by the wings, I pushed him into the fissure by which he is naturally supposed to enter without persuasion. He was soon within the sac, and the inflexed wings of the margin had closed above him, as shown in section, Fig. 17. He is now enclosed in a luminous prison, and his buzzing protests are audible and his vehemence visible from the outside of the sac. Let us suppose that he at length has become reconciled to his condition, and has determined to rationally fulfil the ideal of his environment, as he may perhaps have already done voluntarily before. The buzzing ceases, and our bee is now finding sweet solace for his incarceration in the copious nectar which he finds secreted among the fringy hairs in the upper narrowed portion of the flower, as shown at Fig. 18 A. Having satiated his appet.i.te, he concludes to quit his close quarters. After a few moments of more vehement futile struggling and buzzing, he at length espies, through the pa.s.sage above the nectary fringe, a gleaming light, as from two windows (A). Towards these he now approaches. As he advances the pa.s.sage becomes narrower and narrower, until at length his back is brought against the overhanging stigma (Fig. 18 B). So narrow is the pa.s.s at this point that the efforts of the bee are distinctly manifest from the outside in the distension of the part and the consequent slight change in the droop of the lip. In another moment he has pa.s.sed this ordeal, and his head is seen protruding from the window-like opening (A) on one side of the column. But his struggles are not yet ended, for his egress is still slightly checked by the narrow dimensions of the opening, and also by the detention of the anther, which his thorax has now encountered. A strange etiquette this of the cypripedium, which speeds its parting guest with a sticky plaster smeared all over its back. As the insect works its way beneath the viscid contact, the anther is seen to be drawn outward upon its hinge, and its yellow contents are spread upon the insect's back (Fig. 18 C), verily like a plaster. Catching our bee before he has a chance to escape with his generous floral compliments, we unceremoniously introduce him into another cypripedium blossom, to which, if he were more obliging, he would naturally fly. He loses no time in profiting by his past experience, and is quickly creeping the gantlet, as it were, or braving the needle's eye of this narrow pa.s.sage.

His pollen-smeared thorax is soon crowding beneath the overhanging stigma again, whose forward-pointed papillae sc.r.a.pe off a portion of it (Fig. 18 B), thus insuring the cross-fertilizing of the flower, the bee receiving a fresh effusion of cypripedium compliments piled upon the first as he says ”good-bye.” It is doubtful whether in his natural life he ever fully effaces the telltale effects of this demonstrative _au revoir_.

[Ill.u.s.tration: Fig. 18 A]

Such, with slight modifications, is the plan evolved by the whole cypripedium tribe. Darwin mentions bees as the implied fertilizers, and doubtless many of the smaller bees do effect cross-fertilization in the smaller species. But the more ample pa.s.sage in acaule would suggest the medium-sized Bombus as better adapted--as the experiment herewith pictured from my own experience many times would seem to verify, while a honey-bee introduced into the flower failed to fulfil the demonstration, emerging at the little doorway above without a sign of the cordial parting token.

[Ill.u.s.tration: Fig. 18 B]

Occasionally I suppose a fool b.u.mblebee is entrapped within the petal bower and fails to find the proper exit, or it may be--much less a fool--having run the gantlet once too often, decides to escape the ordeal; hence the occasional mutilated blossom already described.

One of the most beautiful of our orchids, though its claims to admiration in this instance are chiefly confined to the foliage, is the common ”Rattlesnake-Plantain,” its prostrate rosettes of exquisitely white reticulated leaves carpeting many a nook in the shadows of the hemlocks, its dense spikes of yellowish-white blossoms signalling their welcome to the bees, and fully compensating in interest what they may lack in other attractive attributes.

[Ill.u.s.tration: Fig. 18 C]

The single flower is shown enlarged in Fig. 19--A, a young blossom, with a.n.a.lyses B and C, the latter indexed; D, an older blossom, with similar a.n.a.lyses (E and F). Both sorts are to be found upon every spike of bloom, as the inflorescence begins at the base and proceeds upward. As we look into the more open flower we observe a dark-colored speck, which, by a.n.a.lysis, proves to be the lid of the anther. This portion is further shown enlarged in Fig. 20, A. If we gently lift it with a pin, we disclose the pollen ma.s.ses in the cavity (B) thus opened (C, profile section), the two pairs united to a common viscid gland at the base, this gland again secreted behind a veil of moist membrane, as also shown at B. This membrane is, moreover, very sensitive to the touch. Below the flattened tip of the column, and at a sharp inward angle, is the stigma.

In the freshly opened flower (Fig. 19, A) the column inclines forward, bringing the anther low down, and its base directly opposite the V-shaped orifice in the lip, which also is quite firmly closed beneath the equally converging upper hood of the blossom. The entrance is thus much narrowed. If we insert a pin in this V-shaped entrance it comes in contact with the sensitive membrane below the anther, and it is immediately ruptured, as shown at Fig. 20, D. The sticky gland is brought into immediate contact, and clasps the pin, which, now being withdrawn, brings away the pollen, as in E and F. Thus it is naturally removed on the tongue of its sipping bee.

[Ill.u.s.tration: Fig. 19]

[Ill.u.s.tration: Fig. 21]

The further demonstration will be better shown by profile sections (Fig.

21). Nectar is secreted in the hollow of the lip indicated, somewhat as in the cypripedium. If we now imitate with a probe the habit of the insect and the action of its tongue, we may witness a beautiful contrivance for cross-fertilization. We will suppose the bee to be working at the top of the spike. He thrusts his tongue into the narrow opening (G). The membrane protecting the pollen-gland, thus surely touched, ruptures as described, and the exposed gland attaches itself to the tongue, being withdrawn as at H, and located on the insect's tongue, as in F, Fig. 20. The bee leaves this flower cl.u.s.ter and flies to another, upon which it will usually begin operation at the bottom. The flower thus first encountered is an old bloom, as in Fig. 19, D. Its sepals are more spreading, the lip slightly lowered, and the column so changed as to present the plane of the stigma, before out of sight, in such a new position as to invariably receive the pollen. The tongue of a bee entering this flower conveys the pollen directly against the stigmatic surface (I), which retains its disentangled fecundating grains, as at J, and the flower's functional adaptations are fulfilled.

[Ill.u.s.tration: Fig. 20]

[Ill.u.s.tration: A. Extended. B. Folded beneath the head.]