New Zealand Plants and their Story
The Struggle for Existence
The Struggle for Existence.
Putting on one side the question whether our plants came by land or were conveyed by winds, birds, or water, and granting that they finally got a foothold, it will be seen that soon a struggle would arise between these newcomers for the possession of the soil. Such a strife would be somewhat analogous to that which has taken place between our colonists themselves, and has resulted in riches for some and poverty for others.page 8
Every one who cultivates a garden, however small, has to cope with what are called weeds—i.e., with the plants equipped in some special manner for occupying the soil at the expense of others. A species that can rapidly reproduce itself from seed, or by suckers, creeping stems, and the like, has a great advantage over one of slower propagating-power, and will soon smother it out by force of numbers alone. Some plants have large leaves, which they flatten against the ground, and so occupy at once more than their share of the soil. Others have a peculiar taste, making them objectionable to snails, slugs, or insects, and so triumph over plants liable to the attacks of such animals. But there is no need to multiply instances; any one interested can search for examples, and a most fascinating quest it is.* The advantages in some cases are so small as not to be appreciable by us; but, however slight the benefit, the plant possessing it must conquer in the long-run.
In nature this strife between plants is always in progress—a silent but nevertheless a deadly conflict. The calm aisles of a forest are a battlefield where the trees, shrubs, and more lowly plants strive for the mastery, while at the same time the forest itself wages incessant war with the adjoining grass-land—the one or the other aided by climatic changes, an abundant rainfall favouring the forest and drier conditions the meadow. Thus, when the plant immigrants arrived from the north and from the south, these two bands of invaders from quite different regions, and not attuned to each other, would engage in fierce battle; many would fall, and those escaping would be driven into inhospitable spots.
What may be accepted as traces of such warfare are still to be encountered. For instance, the beech (Nothojagus) forests may be taken as typical of southern South America—of stormy Fuegia, in fact—while the ordinary New Zealand mixed forest represents, in part, one band of subtropical invaders. This latter forest is the common "bush" of New Zealand, extending from the extreme north of the region to the south of Stewart Island, and even to the distant Aucklands. But near Chelsea, a suburb of Auckland City, may be seen some New Zealand beech-trees. Other isolated groups exist farther north, and even reach that most charming spot, the Little Barrier Island. These solitary trees are doubtless remnants of a page 9battalion of the great subantarctic or antarctic plant army, held now in bondage by their northern conquerors. Farther south the beeches are more powerful; but, driven from the fertile land, they occupy the poorer soil of the lowlands or the inhospitable mountainslopes, where they oppose a solid front to the biting blasts.
A remarkable example of the restricted distribution of a tree is shown by the kowhai of Chatham Island. This plant is common on certain volcanic ground near Auckland City. It was formerly extremely abundant in the Catlin's River forest, and in fact is found all over New Zealand, growing in various distinct kinds of soil. But in Chatham Island you may search the forest everywhere and find no trace of this graceful tree except on the limestone country near the edge of that extensive lagoon, the Whanga. There it is abundant, in company with the ordinary trees of a Chatham Island lowland forest, which latter elsewhere occupies volcanic ground. Here, then, is some slight advantage, not yet estimated by science, afforded to the ordinary trees by the volcanic soil which enables them to exclude the kowhai; whereas the limestone soil does not afford this benefit, and there all the trees meet on equal terms, flourishing side by side.
How many plants of which no trace has been found may have existed in New Zealand, and may have been destroyed through changes of conditions leading to some slight advantage for their competitors, none can tell; but that many ancient types of surpassing interest must have so perished is quite well known from such fossil plants as have been found, and amongst which, side by side with existing genera, are others not now to be found in any part of Australasia.
* This matter is gone into again in Chapter IX.