Pollen

“ As they rise to fly away after sucking, the pollen masses which have attached themselves to the hairs on the lower part of their legs are drawn out, to be transferred to other blossoms, perhaps today, perhaps not for a fortnight. ”

“ 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. ”

“ In the mean while plenty of barren flowers are produced on a distinct root, on short straight stalks, from which they rise like little separate white bubbles, suddenly expanding when they reach the surface, and floating about in such abundance as to cover it entirely. Thus their pollen is scattered over the stigmas of the first-mentioned blossoms, whose stalks soon afterwards resume their spiral figure, and the fruit comes to maturity at the bottom of the water. ”

“ When the pollen is of full size, or ripe, the little box bursts open, and out the pollen flies. The growth of the plant begins here, with the pollen.
A tiny grain of pollen, falling on the top of the pistil, begins to grow. It puts out little threads like roots. These grow down the stem, or post, of the pistil into the seed case. There they find the seed germs, and when the pollen comes to them, the germs begin to grow. They grow very fast.
It is then that the pretty flowers fade. The work of the blossom is done when the pollen is ripe, and the seed germs begin to grow. ”

“ 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. ”

“ Bees, wasps, flies butterflies, and beetles could not be kept away from an entertainer so generous; for while the nectar in the deep, tubular brown florets may be drained only by long, slender tongues, pollen is accessible to all. Any one who has had a jar of these yellow daisies standing on a polished table indoors, and tried to keep its surface free from a ring of golden dust around the flowers, knows how abundant their pollen is. The black-eyed Susan, like the English sparrow, has come to stay--let farmers and law-makers do what they will. ”

“ I will not insult the intelligence of the reader at the present time of day by telling him that pollen is usually transferred from blossom to blossom in one or other of these two chief ways—it is carried on the heads or bodies of bees and other honey-seeking insects, or else it is wafted on the wings of the wind to the sensitive surface of a sister-flower. ”

“ The pollen from a rose will not make the seed germs of a lily grow. The tulip can do nothing with pollen from a honeysuckle. [Pg 62] The pollen of a buttercup is not wanted by any flower but a buttercup. So of all. The pollen to do the germ any good must come from a flower of its own kind.
What is to be done in this case? How will the insect get the pollen to the right flower? Will it not waste the clover pollen on a daisy?
Now here comes in a very strange habit of the insect. Insects fly “from flower to flower,” but they go from flowers of one kind to other flowers of the same kind. ”

“ In such plants, the pollen is conveyed from the male flowers to the female by the wind, and to this end the former are usually placed above the latter so that these are dusted with the pollen whenever the plant is shaken by the wind. In these plants, the male flowers often outnumber the female enormously, and the pollen is produced in great quantities, and the stigmas are long and often feathery, so as to catch the pollen readily. ”

“ In species where the pollen is wind-borne as in most of our trees—firs, oaks, beech, ash, elm, etc., and many herbaceous plants, the flowers are as a rule small and inconspicuous, greenish, and without either scent or honey. Moreover, they generally flower early, so that the pollen may not be intercepted by the leaves, but may have a better chance of reaching another flower. And they produce an immense quantity of pollen, as otherwise there would be little chance that any would reach the female flower. Every one must have noticed the clouds of pollen produced by [Pg 123] the Scotch Fir. ”

“ The pollen bags fit closely round the stigma, and so when pollen drops from them it does not fall out of the flower, for its passage is blocked by the tight-fitting pollen bags. When the bee comes, she has to push her tongue right up the spur, and in doing this she forces it past the pollen bags. ”

“ The Pollen, though to the naked eye a fine powder, and light enough to be wafted along by the air, is so curiously formed, and so various in different plants, as to be an interesting and popular object for the microscope. ”

“ You see your eyes were not meant to look at things so tiny as pollen grains. You can see a common ball or even a small shot very well indeed; but when it comes to pollen grains you are as blind as a mole. ”

“ All the pollen and honey must be brought into the hive by them. Have you ever seen the little baskets which working bees have for carrying pollen? Perhaps you do not know what pollen is. Well, some day look right down in the centre of a flower and you will find some fine yellow powder. That is pollen, or bee bread, and the bees are very fond of it. On the hind leg of the worker is a nice smooth place, and on each side of it are stiff, curved hairs which cover it over. Into this little cage the bees push the pollen, then fly swiftly away toward the hive. ”

“ Since the pollen of many plants is sticky and moist it adheres to the surface of the basket. Dry pollen is moistened by saliva, so that it also sticks,— [Translation from Fleischmann and Zander. 1910.] ”

“ The mode in which they accumulate the pollen, and the mechanism of its conveyance from hair to hair till it reaches the part of the body it must attain in order to be removed for packing in the cells, is not fully understood, but it appears to be accomplished by complex correlative actions of various parts; the head and the front legs scratch up the pollen, the legs move with great rapidity, and the pollen ultimately reaches its destination. ”

“ Fig. 236 shows you another blossom from [Pg 228] this same plant. The stamens have shed their pollen, and are quite dry and withered; but its pistil has straightened itself, and spreads out its four tips so as to receive the pollen from another flower.
Fig. 237
It is believed that those seeds which are touched with life by pollen from another flower are more likely to change into healthy, hardy plants than those which are quickened by the pollen of their own flower. ”

“ These two have been selected as illustrating two peculiar adaptations in the weight of pollen or pollen-holding flowers that is common to some other submerged aquatic plants. In one the male flower, or pollen from it, with the very nicest adjustment of function to environment in all the realm of the plant world, is just of the right specific gravity to float to the surface with dramatic suddenness and perfectly timed effectiveness. ”

“ In these, and hundreds of other plants, the wind will blow great clouds of pollen through the air. When we stop to consider that a single, or at most a very few pollen grains are all that are necessary—in fact, are all that can be of real service—the enormous wastage of the male fertilizing substance, in order that mating be secured, gives us some idea of how prodigal is nature in this supreme function. ”

“ The yellow powdery substance with which we are all familiar in ordinary flowers is here absent, the pollen being collected in two club-shaped or, more properly, spatula-shaped masses, linked in pairs at their slender prolonged tips, each of which terminates in a sticky disc-shaped appendage united in V-shape below. These pollen masses are concealed in pockets (B) around the cylindrical centre of the flower, the discs only being exposed at the surface, at five equidistant points around its rim, where they lie in wait for the first unwary foot [Pg 231] that shall touch them. ”

“ Many of these tree blossoms are neither bright enough to attract the attention of the bees and butterflies, nor so fragrant as to tempt the passing insects to visit them; for when the flower handkerchiefs are not large and bright enough to signal the bees, the blossom often gives notice of its presence by a strong perfume. How, then, is the pollen from one flower to reach the pistil of another? ”

“ Pollen in such plants is much modified, and instead of being in the ordinary form of pollen grains, it is, at the time of ripening, lengthened out into tubular, hairlike structures. These delicate prolongations of the male fertilizing stuff are carried by the currents of the water, just as a thread would be, but with the difference that the pollen threads are so beautifully weighted to fit their watery environment that they float, suspended, in the depths of the water at or near the level of the female flowers. ”

“ Rose-growers are always trying hard to make new kinds by mixing the pollen. The pollen, you remember, is the yellow powder on the little tips of the stamens. These tips, as I believe I told you, are called anthers, and the slender part of the stamen is the filament. ”

“ In some plants, such as the beet, both wind and insects play an important part in the spread of pollen. In all cereals and grasses, and in the potato, the pollen is carried mainly by wind. In most of our common plants of garden, field, and orchard, insects are the chief and most effective carriers of pollen. The following is a list of insect-pollinated plants: Onions, asparagus, buckwheat, gooseberry, currant, cabbage, radish, turnip, raspberry, blackberry, strawberry, apple, pear, plum, cherry, peach, alfalfa, clover, melons, cucumbers and squashes. ”

“ The wind carries this pollen.
Find out how the silk is fitted for catching the pollen. What is the need for the great quantity of pollen that the plant produces? [Pg 164]
Strip off the husks and compare the tough, hard husks that are found on the outside with the soft paper-like husks found close to the cob. Show how each kind is fitted for its particular work. ”

“ The pollen, on which food alone the young bees are fed, is gathered and stored among rows of hairs on the legs, and in the more highly specialized forms it is wetted with honey so as to form a compact mass, easily carried and easily removed when the nest is reached. The balls of pollen thus formed are sometimes nearly the size of the body of the bee, and may contain one to two hundred thousand grains of pollen. ”

“ Reasoning from the lower forms of life, he points out the fact that the ovules, developed in the female organs of plants, must be nourished for a time after fertilization; hence the pollen is necessarily brought to them—being conveyed to the stigma by insects, by winds, or by the spontaneous movements of the stamens themselves, upon which the pollen grows. ”

“ 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. ”

“ In return for the "treat" which the flowers give, the insects render a valuable service to the plants.
Fig. 3.—Honey Pouch and Pollen Pods.
I must remind you of something we have looked into before in "Picciola" (February 14, 1882) , and that is that every perfect seed is the result of a partnership entered into by the pollen grains and the ovules of a flower. The pollen is the yellow dust which it is so easy to see on lilies and some other flowers; the ovules are little round bodies lying in the swollen part of a flower where it joins the stem. ”

“ The conveyance of pollen from one flower to another in cross-fertilization is effected naturally by the wind, or by the agency of insects and other creatures. Flowers that require the aid of insects usually offer some attraction to their visitors in the shape of bright colour, fragrance or sweet juices. The colour and markings of a flower often serve to guide the insects to the honey, in the obtaining of which they are compelled either to remove or to deposit pollen. ”

“ Nature has several interesting ways of bringing about pollination. In the corn, willow, and pine the pollen is picked up by the wind and carried away. Much of it is lost, but some reaches the stigmas, or receptive parts, of other corn, willow, or pine flowers. This is a very wasteful method, and all plants using it must provide much pollen.
Many plants employ a much better method. They have learned how to make insects bear their pollen. ”

“ If he would explain why certain flowers are not colored at all, and how it has come about that other flowers are colored, some in chromatic harmony, and others not, he must look to the flowers themselves, and to their servants the insects. Every one knows that the pollen must find its way from the anther to the stigma, else the flower, lacking impregnation, can set no seed. For many trees, and for grasses generally, the office of transporting the pollen is performed by the wind. ”