OUR NATIVE FLORA.

Auckland Star, Volume LV, Issue 248, 18 October 1924, Page 26

OUR NATIVE FLORA.

A BOTANIST'S JOTTINGS. THE WILES OF A BOTTLEBRUSH (MARGUERITE W. CROOKES, M.A.) Few pt'ople seeing our modestly attired rcwa rewa (or native honeyFlicklo as it pomntimes called) with its ppravs of dark brown or red brown I flowers, would dream of associating it with the flamboyant bottle brushes or I the elejrant. and aristocratic silvertrees ' nf our gardens and parks. Nevertheless it belongs to the same remarkable family, ami though it does not devote so much attention to "the putting on of raiment" as the South African silver tree, or produce such brilliant and striking flowers as its Australian relatives, the bottle brushes, it is quite as interesting from a point of view of the studpiit of nature. The. rcwa vnva was christened by the early settlers "the native honeysuckle." As a matter of fact it is not a monitor of the honeysuckle family at all and is not even distantly connected with them. It is quite common in the bush throughout the North Island and is also found in the Marlborough district of the Sou,th Tsland, and has the additional merit of being quite easy to recognise. It is a fairly large tree, sometimes reaching as much as a hundred feet. Its branches are not spreading, and seen at a distance it rather resembles the Lombardy poplar. It bears long and narrow leaves from four to eight inches in length. They are stiff and roughly j toothed and lighter in colour than most New Zealand leaves. They grow singly, that is to say, each leaf stalk bears only one leaf and not several as do the leaf stalks of the rose or the Virginia creeper. During the months of November and December, however, our rewa rewa is particularly easy to recognise, as it is in flower and its flowers are like nothing else in the New Zealand bush, and indeed they have so many points of interest that it seems a pity to let the month go by without some mention of them. A Complicated Bottlebrush. Seen in the bud they resemble nothing so much as a large bottlebrush with brown velvet bristles. Each "bristle" is a separate flower bud. Now in order to appreciate the cleverness of the bottlebrush flower we must consider the parts in detail. First of all we have organs producing pollen and known as the "stamens." The pollen is produced in little compartments, which burst open and shed it. Most flowers produce pollen of a beautiful golden colour, though some favour different. ehadee of brown, while the New Zealand fuchsia i with that capacity for doing the un- ' usual characteristic of New. Zealand plants has pollen of a vivid and beauti- ■ ful blue. But the pollen is useless to ' the flower, until it has been transferred from the stamen to another organ known as the pistil which will eventually produce the seed. But it is not sufficient that the pollen should alight on the pistil. It must light on one particular part of the pistil otherwise it will be wasted and simply wither! away. The particular part arranged | for its reception is very sticky and known as the stigma. As soon as a pollen grain alights on the stigma it becomes firmly glued on to it and in a' little while it starts to grow. It sends a tiny microscopic tube right down into the heart of the pistil. When this jittte tnbe has finished growing a certain part of the pollen grain passes, down it, and unites itself with a certain microscopic cell contained in the lieart of the pistil. When tk'fe process lias once taken place the work of seedmaking can go on merrily. M*hcn the pollen has once been deposited on the stigma everything is "plain sailing." The difficulty in transferrin pollen lies in the fact that the stigma must (usually) be pollinated by pollen from another flower, otherwise unhealthy offspring will result. Preparing for Action. Now if we return to consider our bottlebrush in the light of these facts we shall see that it is faced with two problems. (1) How can it contrive to secure pollination by the pollen of another bottlebrush; (2) How can it prevent itself being accidentally pollinated by pollen from its own stamens? Its method is most ingenious. In the first place the pollen of the stamens ripens before the bud opens. Now, as the bud is tube-like it has a small diameter, and as the pistil is swollen, it follows that masses of the ripe, pollen become deposited on it. But surely, one would say, if the pollen is deposited on the pistil, will not that produce self-pollina-tion, the very evil that the plant is endeavouring to avoid? It certainly seems bo at first sight and indeed the early botanists who considered this matter declared that the bottlebrush family •were self-pollinated. But this is not bo for two reasons. In the first place the stigma is safely hidden in a cupshaped hollow at the top of the pistil, and in the second place the stigma is not at this stage of its existence mature, so that if an odd grain of pollen does chance to fall on it, it will not produce any effect. When the stamens have deposited their pollen the flower sets about opening. One would expect that would be a straight forward matter enough, just a gradual breaking apart of the four segments of the tube. But nothing so orthodox satisfies our rcwarcwa. First, the tube opens a little at the top so as to expose the stigma, then it splits into four parts about the region of the base, but the greater part of it still remains closed. Then suddenly, without any warning, the whole thing bursts open and the four segments of the tube, which are elastic, roll back and form themselves into curious little twists and coils. The pistil alone remains standing upright with large masses of pollen upon it. The bottlebrush at thi3 stage has a most bizarre appearance. Indeed it looks quite like a collection of little coiling brown worms, with the sturdy pistils projecting oat from the midst of them. Now we have the whole stage set for the final net of pollination. How is it brought about? Most flowers are pollinated either by insects of scene sort or by the wind. But it is not bo in this case and our bottlebrush, by the manufacture of a liberal supply of honey, has secured unto itaelf the attentions of an even more picturesque visitor, namely, the tui, or his etill more attractive relative, the bellbird. To secure the honey our friend the tui dives his beak in among a cluster of flowere and in this way receives the pollen from the upstanding pistils on the front of his head, and flying away he obligingly deposits it accidentally upon the ripened stigma of a more fully developed cluster A n ff tlm3 lv cr T>-P°l"nation i 8 secured. After pollination has taken place the eccde arc developed in a hard woody Bccd case consisting of three compartments, yhieh eventually split open an* Iβ sent intq tho world. '

Our rewa rewa is not only of scientific, but also of economic interest.. It produces wood of an extremely decorative character which is much valued by cabinetmakers for inlay work and so on. Apart from its many good qualities it has the reputation of being one of the most difficult woods in the bush to set fire to, and for this reason it was christened by the early settlers the "bucket "of water tree"—a name by which it is still known in some parte of the country. Taking it for all in all it is a tree that well repays observation.