Poinsettia

“ I have forgotten much, but still remember
The poinsettia's red, blood-red in warm December. ”

“ Cut flowers always afford joy, from an inexpensive bunch of carnations to the choicest American Beauties. The Christmas blooming plants, however, last much longer, and the rich scarlet berries of the ardesia will survive the holiday season by several months. Poinsettia has been steadily increasing in popularity, and can be surrounded by ferns that will live on indefinitely. All the decorative [131] foliage plants are sure to be welcomed, for with care they will last for years, and improve in size and beauty.
The growing fad for winter-blooming bulbs affords another opportunity for pleasing. ”

“ They require good turfy loam, with an addition of one-sixth of leaf-mould and a little sand, and should be kept in a heat from 65° to 70° at night, with a rise of 10° by day. To prevent their growing lanky, they should be kept with their heads almost touching the glass ”

“ Hence, when certain definite points of the flower are touched by an insect, the pollinia are shot forth like an arrow, not barbed however, but having a blunt and excessively adhesive point. The insect, disturbed by so sharp a blow, or after having eaten its fill, flies sooner or later away to a female plant, and, whilst standing in the same position as before, the pollen-bearing end of the arrow is inserted into the stigmatic cavity, and a mass of pollen is left on its viscid surface. Thus, and thus alone, can the five species of Catasetum which I have examined be fertilised. ”

“ But the stamens, being shorter than even the germen, cannot discharge the pollen so as to throw it upon the stigma, as the flower stands always upright till after impregnation. And hence, without some additional and peculiar aid, the pollen must necessarily fall down to the bottom of the flower. Now, the aid that nature has furnished in this case, is that of the Tiputa Pennicornis, a small insect, which, entering the tube of the corolla in quest of honey, descends to the bottom, and rummages about till it becomes quite covered with pollen ”

“ It might with the sweet-pea, but even if it did, the pollen from the same flower is not as good as the pollen from another flower from a different plant, and the seed would be poor and the plants would grow weaker every year. There are many insects that act as servants to the flowers, and the wind is one of the servants, too. It shakes the corn-tassel so that the pollen falls on the silk and makes the ear, and it carries the pollen of one stalk to the silk of another—sometimes from one field to another. ”

“ The honey is secreted in the perianth-tube, and the insects, endeavouring to obtain it through the narrow passages at the base of the stamens, settle upon the outer perianth-leaves, which are bent backwards and often very hairy along their central line. The insects then rub their backs on the anthers just above them, beneath the branches of the style; they readily deposit the pollen on the stigma of another flower as they enter it, but cannot do so in withdrawing, since the stigma is pushed back, and self-fertilisation is thus avoided. ”

“ When an insect with the pollinia attached to its back or head enters another flower, the easy depression of the distal portion of the labellum probably plays an important part; for the pollen-masses are extremely friable, and if they were struck against the tips of the petals much of the pollen would be lost; but as it is, an open gangway is offered, and the viscid stigma, with its lower protuberant part lying in front, is the first object against which the pollen-masses projecting forwards from the insect's head or back would naturally strike. ”

“ We push the point gently down the spur, when a part of the pencil touches against the rostellum and presses it down, touches lightly the viscid feet of the pollen masses (pollinia) , and as the pencil is withdrawn both come with it, and stick out from it like a pair of horns. Be careful to hold the pencil in the exact position it now occupies, and watch. The heavy heads of the pollinia are drooping forward, but after a few minutes they cease to fall lower. Now push the pencil into this other flower. The pollen-masses go directly to the stigma, and some of the pollen is detached. ”

“ Small insects alight on the labellum for the sake of the nectar copiously secreted by it; as they lick this they slowly crawl up its narrowed surface until their heads stand directly beneath the overarching crest of the rostellum; when they raise their heads they touch the crest; this then explodes, and the pollinia are instantly and firmly cemented to their heads. As soon as the insect flies away, it withdraws the pollinia, carries them to another flower, and there leaves masses of the friable pollen on the adhesive stigma. ”

“ The bee that creeps down into the flower for a sip of nectar releases a tiny spring, like a mouse entering a trap. The released anther flies up and dusts its pollen on the hairy body of the insect. Now, if you take this pollen and put it under a good microscope, you will see that each grain is in reality a cluster of four tiny balls resembling oranges. Indeed, in passing it may be observed that each species of plant seems to possess some special whim in the shape of its pollen, with its own peculiar devices of exterior decoration and structural form. ”

“ More than that, some are absolutely sterile to their own pollen when it is applied to their stigmas artificially! With insect aid, however, a single plant has produced more than 1,000,700 seeds. No wonder, then, that as a family, they have adopted the most marvellous blandishments and mechanism in the whole floral kingdom to secure the visits of that special insect to which each is adapted, and, having secured him, to compel him unwittingly to do their bidding. ”

“ Now any plant which, owing to chemical causes, favourable position, etc., developed an unusually brilliant colour, would be likely to attract the attention of a winged insect in search of pollen-food. The insect, by alighting on a second flower soon after, would fertilise it with the pollen of the first flower that adhered to its limbs, thus securing to the plant the advantages of cross-fertilisation. Thanks to the laws of heredity, this advantage would be transmitted to the young plants, among which again those most favoured would gain an advantage and a more numerous offspring. ”

“ If a bee dusted with loose pollen visits flowers of another species, it will not long retain pollen in sufficient quantity to effectually fertilize flowers of the original species. On the other hand, if an insect returns at any time during the day, or even after a few days, to the species of Asclepias from which it got a load of pollinia, it may bring with it all or most of the pollinia which it has carried from the first plants visited. The firmness with which the pollinia keep their hold on the insect is one of the best adaptations for cross-fertilization. ”

“ During most years the pollen-masses of the many hundred flowers which were examined, adhered with the rarest exceptions to the stigma, with their discs still enclosed within the pouches. But in the year 1868, from some cause the nature of which I cannot conjecture, out of 116 flowers gathered in two localities in Kent, seventy-five retained both pollinia in their cells; ten had one pollinium, and only thirty-one had both adhering to the stigma. Long and often as I have watched plants of the Bee Ophrys, I have never seen one visited by any insect. ”

“ Yet the pistil of each cabbage-flower is surrounded not only by its own six stamens but by those of the many other flowers on the same plant; and the pollen of each flower readily gets on its stigma without insect agency; for I have found that plants carefully protected from insects produce the full number of pods. How, then, comes it that such a vast number of the seedlings are mongrelized? It must arise from the pollen of a distinct variety having a prepotent effect over the flower's own pollen ”

“ The pollinia, though thus attached, cannot, of course, be removed from their anther-cells without the aid of insects. In this species it seems possible (though, from the position of parts, not probable) that an insect might drag the pollinia out and leave them on the stigma of the same flower. ”

“ In selecting honey-producing plants, it should be the aim of the bee-keeper to plant such as would be of benefit to stock or poultry as well as bees. Now I find that my poultry will eat the seed of the Polanisia in a short time as readily as buckwheat; and there is no plant on my farm that stands the drouth equal to it. At present (July 25th) we are having a very severe drouth and extreme heat, yet with the temperature ranging from 90° to 108° in the shade, not a leaf of the Polanisia wilts; on the contrary, it is making a very rapid growth. ”

“ But as the column of Spiranthes after a time moves from the labellum, leaving a free passage for the introduction of the pollinia, so here the rostellum moves backwards, and not only recovers its former arched position, but stands upright, leaving the stigmatic surface, now rendered more adhesive, perfectly free for pollen to be left on it. The pollen-masses, when once cemented to an insect's forehead, will remain attached to it, until they are brought into contact with the stigma of a mature flower ”

“ We shall, moreover, presently see that Catasetum is exclusively a male form; so that the pollen-masses must be transported to the female plant, in order that seed should be produced. The pollinium is furnished with a viscid disc of huge size; but this, instead of being placed in a position likely to touch and adhere to an insect visiting the flower, is turned inwards and lies close to the upper and back surface of a chamber, which must be called the stigmatic chamber, though functionless as a stigma. There is nothing in this chamber to attract insects ”

“ In many flowers, the stamens, as they ripen, move so as to place themselves directly before the entrance to the nectary, where they are necessarily struck by any insect searching for honey; after the pollen is shed, they move aside or bend downward, and their place is taken by the pistil, so that an insect which has come from a younger flower will strike the part of the body previously dusted with pollen against the stigma, and deposit the pollen upon it. ”

“ All these species, with the exception of the Neotinea, require the aid of insects for their fertilisation. This is obvious from the fact that the pollinia are so closely embedded in the anther-cells, and the ball of viscid matter in the pouch-formed rostellum, that they cannot be shaken out by violence. We have also seen that the pollinia do not assume the proper position, for striking the stigmatic surface until some time has elapsed; and this indicates that they are adapted to fertilise, not their own flowers, but those on a distinct plant. ”

“ And not only expressions of welcome, but each with some perfect little plan of its own to make this insect guest the bearer of its pollen to the stigma of another flower of the same species. And how endless are the plans and devices to insure this beautiful scheme! Some flowers make it certain by keeping the stigma closed tight until all its pollen is shed; others place the anther so far away from the stigma as to make pollen contact impossible; others actually imprison these pollen-bringing insects until they can send them away with fresh pollen all over their bodies. ”

“ The pistil merely opens up a bit and down travels the powder into the seed vessel to help form seed. There would be no real fertile seed without the pollen.
"Sometimes the pollen from one flower falls on its own pistil, sometimes the wind, the bees, the birds carry the pollen to flowers far off and drop it on their pistils. Marvelous, is it not? Everything has to be just right, or the pollen does not do its work nor the pistil, either. Pollen has to be ripe to help make the seed. ”

“ Within the stigmas of many other flowers pollen-leaves were observed. The plant produces plenty of seed; and thirteen of the twenty-one lower flowers on one spike had formed large capsules.
We will now turn to some exotic genera. The pollinia of Pleurothallis frolifera and ligulata (?) have a minute caudicle, and mechanical aid is requisite to force the viscid matter from the under side of the rostellum into the anther, thus to catch the caudicles and remove the pollinia. ”

“ No doubt you have already learned that plants can make better and stronger seeds when they can get the pollen dust from other plants. But I am sure that you will be very much surprised to hear that the colors, the scent, and the curious shapes of the flowers are all so many baits to attract insects. And for what reason? In order that the insects may come and carry the pollen dust from one plant to another.
So far as we know, it is entirely for this purpose that the plants form honey in different parts of the flower. ”

“ The polinnia cannot, as I have often proved, be shaken out of the anther-cells. That insects of some kind visit the flowers, though not frequently, and remove the pollinia, is certain, as we shall immediately see. Twice I have found abundant pollen on the stigmas of flowers, in which both polinnia were still in their cells; and no doubt this might have been much oftener observed. The elongated labellum affords a good landing-place for insects: at its base, just beneath the stigma, there is a rather deep depression, representing the nectary in Orchis ”