Veronica presents great difficulties to the systematist. Many of the species are singularly protean in habit, foliage, and inflorescence, varying so much in appearance that it is no easy matter to fix their real limits. Intermediate forms are numerous, connecting species that would otherwise appear most distinct, and in not a few cases these intermediates blend so freely into one another that an apparently continuous series of forms is produced, while several species hybridise so readily in cultivation that the supposition at once arises that natural hybrids may also occur. So great has been the difficulty in deciding what are the limits of the species, and in properly characterizing them, that the late Baron Mueller, in his little book on the vegetation of the Chatham Islands, boldly proposed to solve the question by referring no less than 13 of the species considered to be distinct by Hooker to a collective species to which he gave the new name of V. Forsferi! It is hardly necessary to say that this extreme view has not received the sanction of any botanist familiar with the vegetation of the colony.
Two papers of considerable importance dealing with the New Zealand species have appeared since the publication of the Handbook. The first is Mr. Armstrong's "Synopsis of the New Zealand Species of Veronica" (Trans. N.Z. Inst. xiii. 344). This is mainly based on observations made during the author's explorations in the Alps of Canterbury, and on the study of the fine collection of living plants which he had amassed in the Christchurch Botanical Gardens. It contains descriptions of a considerable number of new species, and many observations of value. Unfortunately, Mr. Armstrong did not distribute types of his new species, so that in some cases their identification is uncertain. The second is Mr. Kirk's "Notes on certain Veronicas" (Trans. N.Z. Inst. xxviii. 515). In this Mr. Kirk transfers to the genus those species which had been erroneously placed in Logania and Mitrasacme by previous authors. Descriptions are also given of five or six new forms, in addition to much new matter bearing on the geographical distribution, &c., of the species already known. Another contribution of considerable value consists of the coloured drawings and descriptions published from time to time by Sir J. D. Hooker in the Botanical Magazine. Altogether, about 20 species have been beautifully illustrated and described by him, the value of the descriptions being enhanced by the critical notes which accompany them. Since the publication of the Handbook, too, the important fact has been made known by Kirk and others that the whole of the species with minute scale-like leaves (answering to Section III. of the following conspectus) have dimorphic foliage, the leaves of the young state being widely different from those of the mature plant. It has also been shown that these early leaves are often produced by reversion on old specimens, especially when cultivated in a cool and moist situation. The student will find the early leaves of several species fully described in the excellent series of papers on the "Seedling Forms of New Zealand Phænogams," contributed by Mr. Cockayne to the recent volumes of the Transactions of the New Zealand Institute.
I have followed the "Genera Plantarum" and Engler and Prantl's "Naturlichen Pflanzenfamilien" in reducing Hooker's genus Pygmea to Veronica, the differences of a 5- or 6-lobed corolla and leaves not quadrifariously arranged hardly being of generic importance, especially now that it is known that several true Veronicas have a 5-lobed corolla. The arrangement and limitation of the species, and the preparation of the necessary diagnoses, has proved to be a most difficult and perplexing task, and I am far from satisfied with the result. But, imperfect though it may be, it represents many months' assiduous study, and the examination of some thousands of specimens, and is, at any rate, an honest effort to clear away some of the difficulties which have hitherto impeded the study of the genus. I have to acknowledge the great assistance rendered to me by Mr. N. E. Brown, of the Kew Herbarium, in comparing sets of my specimens with the types preserved at Kew, and for many full and valuable notes thereon.
