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Botanical investigations in New Zealand readily fall into two periods, first, those carried out by visiting botanists and second, the work of resident botanists. In the first period, judged by the collections made and the results published, there are three outstanding voyages or groups of voyages: the three voyages (1768–1771; 1772–1775; 1776–1780) of Captain James Cook; the three voyages (1822–1825; 1826–1829; 1837–1840) in which Admiral Dumont d'Urville was either Executive Officer or in command; and the Antarctic Expedition (1839–1843) under Sir James Clark Ross.

These expeditions were all sent out for purposes of discovery, both geographical and scientific; and, though none were primarily for botanical investigation, in each case skilled and enthusiastic botanists were given opportunity to collect and observe plants. Indeed, these botanists gathered a rich harvest of hitherto unknown species.

Rather later, many resident botanists contributed to the botanical exploration of New Zealand. Of these the three that stand out most prominently, on account of the importance of their work, are William Colenso, Thomas Cheeseman, and Leonard Cockayne. The one man that connected the two periods of botanical discovery was Colenso. He began collecting plants in New Zealand six years before the arrival of the Antarctic Expedition, and for more than half a century afterwards corresponded regularly with Sir Joseph Hooker of that expedition.

This bulletin will tell something of the work the visiting botanists did: but before going on to this will explain very briefly how the science of botany has developed.

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The science of botany had its origin in the quest for useful plants, and hence the first books on plants concerned those kinds, chiefly herbs, that produced some substance of real or fancied use, more especially in medicine. The early books were called ‘herbals’ and their authors ‘herbalists’. The earliest herbalist was a Greek, Theophrastus, and after his time scarcely anyone entitled to be called a botanist, other than another Greek herbalist, Dioscorides, appeared for eighteen centuries. Then, that is in the sixteenth century, several herbalists produced large illustrated herbals. These herbalists were not interested in plant classification, some of them merely putting the species in alphabetical order. The first great plant classifiers were Ray in England, Tournefort in France, and Linnaeus in Sweden; and modern systematic botany dates from their times, that is to say, from the middle of the seventeenth to the middle of the eighteenth centuries. Linnaeus was the first to apply to all animal and plant species binomial names, those consisting of a genus name and a species name, such as Phormium tenax, Coprosma robusta. This method was of such great value in handling unlimited numbers of species that immense advances in botany followed. The first classifications, however, were rather artificial, even Linnaeus depending to a large extent on the number of stamens in each flower, and they have been almost entirely replaced by modern systems.

Nowadays, botanists consider the structure of the plant body, its stages of growth, and the method of reproduction; and distinguish four main groups, or sub-kingdoms, of the plant kingdom:

• Thallophytes, the simplest forms of plant life, which include seaweeds, bacteria, fungi, and lichens;

• Bryophytes, such plants as mosses and liverworts, which have more definite form than the Thallophytes;

• Pteridophytes, ferns and allied plants, such as lycopodium;

• Spermophytes, the seed-bearing plants. These are very, numerous, and are further divided into the pines (Gymnosperms) and the true flowering plants (Angiosperms), these latter being called Monocotyledons if they have one seed leaf, Dicotyledons if they have two seed leaves.

In order to show how the plants are related one to another, and to give an exact description for each, botanists then subdivide each group into smaller groups: first into orders, which include a number of families. For example, the lily family (Liliaceae), which belongs to the order Liliales, includes such well known plants as tulips, hyacinths, onions, and asparagus, as well as New Zealand flax, the cabbage tree, and the supplejack. The family is further divided into smaller groups called genera (singular genus), and the genera are divided into different kinds or species (singular species).

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Botanists collecting a plant for the first time have to use all their knowledge of the similarities and differences in plant form to solve a new problem. They want to be able to describe the plant accurately for other people and to assign it a name. J. R. Forster^*, for instance, was the first botanist to publish a description of the supplejack, to which he gave the generic name Rhipogonum, and the specific name scandens^** Before he could do this, however, he had to consider every feature of the plant. He could immediately place it in the sub-kingdom Spermatophyta, as a seed-bearing plant; in the sub-division Angiosperms, because it had flowers; in the class of Monocotyledons, because these have parallel-veined leaves and the parts of the flowers in ‘threes’: in the order Liliales because of the petal-like floral leaves; and in the lily family because the ovary is placed above the floral leaves (perianth).

But he could not, after carefully examining the specimen he had collected and after consulting all the published descriptions of the known genera in the lily family, assign it to any of these. He therefore had to establish or ‘found’ a genus, i.e. to define a group of related species and give it a distinctive name, in this case Rhipogonum, which he made from two Greek words ripos, ‘a pliant twig’ or ‘wickerwork’, and gonu, ‘knee’ or ‘joint’. Then he further distinguished the plant from all others by adding a name for the species, scandens, the Latin for ‘climbing’. (Though there is only one New Zealand species of Rhipogonum, four other species have been discovered in Australia since Forster named the genus.)