5. Die Gattung Acaena.
This volumincus and most painstaking work consists of two parts, the one general and introductory, and the other systematic and floristic. The author has not confined his studies to herbarium material of wild plants, but has searchingly examined the garden forms of Europe, especially those cultivated in the Bremen Botanical Garden, of which he is the director. These horticultural studies have led to the important discovery, first, of undoubted hybrids, and, secondly, of two cases of mutation. The first of these mutants arose from Acaena ovalifolia R. and Pav. in the botanic garden of Christiania, and the plant is described as subsp. glabricaulis; the second originated in the botanic garden of Bremen itself from a plant of A. sericea Jacq. f. var., gracilis Bitter, which had been in cultivation for many years.
Chapter II deals with the principles of a natural arrangement of the species within the genus, and in. Chapter III the importance of the different forms of hairs is considered from both the taxonomic and ecological standpoints. Chapter IV deals with seedling forms, those of six New Zealand members of the genus being described at length. The occurrence of long, many-celled, thin-walled hairs in certain early seedlings, but which are absent in the adults, is noted as requiring, special investigation.
Chapter V deals with the plant-geography of the genus The question as to whether it is primarily subantarctic or the contrary is discussed, and, on the assumption that certain characters are older than others, a plea is established for a northern rather than a southern origin But, on the other hand, it is shown how the present extensive occurrence of species not only in subantarctic South America, but throughout the subantarctic zone as a whole, together with New Zealand and parts of Australia, supports the theory of a southern origin.
Certain cases of discontinuous distribution are cited, especially that of the section Acrobyssinoideae, one species of which A. tasmonica Bitter, is endemic in Tasmania, but all the other species occur in the Chilian Andes from lat 39·50 south to Cape Horn and South Georgia. A. californico Bitter, endemic in California, belongs to a section not otherwise extending north of central Chile and Patagonia.
The occurrence of local forms is much commoner than has been thought hitherto, especially on the isolated subantarctic islands. This discounts considerably the general view that the supposed wide area of certain species was due to carriage of the fruits with their hooked barbs by birds. At the same time, the author considers the occurrence of closely related species in distant localities due to bird-carriage, and cites a Sandwich Island species, with its close relatives in south and central Chile, and the Acrobyssinoideae of the Magellan region and Tasmania, but absent in New Zealand. But such distribution was not frequent enough to hinder the evolution of many local forms.
It is a remarkable fact that the New Zealand species of Acaena possess the following peculiarities not present in members of the genus elsewhere: (1.) A stunted habit of growth, although their foreign allies are robust and large-leaved—as, e.g., the New Zealand forms of the polymorphic A. Sanquisorbae Vahl as compared with the Australian, and the three new species formerly referred to A adscendens Vahl in New Zealand in comparison with the true species of that name and A. laevigata (Ait.) Bitter of South America Nor can the alpine climate be responsible for the marked exhibition of this growth-form in the endemic New Zealand section Microphyllae. since the Chilian Andean species show no such character. (2.) The brownish colour of the leaves in certain varieties of the Sanguisorbae group and in A. microphylla Hook f, and such colouring is present in members of other families of New Zealand alpine plants Grey-coloured leaves, arising either through a covering of wax or through air-spaces between the cells, is another characteristic, but there are Chilian examples of similar phenomena
It would serve no purpose to draw up a synopsis of the author's arrangement of the New Zealand species A really critical study of his work is demanded on this point. Here only some general conclusions are noted regarding the limitations of species, important alterations, and so on.
First, it must be pointed out that a most comprehensive view is taken as to the species themselves, so that the polymorphic species are groups which do not exist at all as true entities. These species are subdivided into smaller but still comprehensive groups as subspecies, these into varieties which are the true entities of the flora, and these occasionally into forms.
A subspecies of A. avina A. Cunnn. is created called nanella Bitter, based on specimens sent by Cockayne to Berlin as introduced and collected on the Canterbury Plains, the author considering the stunted habit of specific importance.
Acaeno adscendens Vahl, hitherto supposed to extend to New Zealand, is restricted to plants of the Magellan region and Kerguelenland, while the New Zealand forms referred to A. adscendens are treated by the author as three distinct species—A. saccaticupula Bitter, A. hirsutula Bitter, and A. fissistipula Bitter, the two latter being closely related, but the former coming into a different subsection allied to that containing A. adscenden [ unclear: ] . Varieties are also described of all three species.
Acaena Sanguisorbae Vahl is restricted to Australian, Tasmanian, and New Zealand plants, the Tristan d'Acunha plant being referred to A. sarmentosa Car-michael and considered as restricted to that group, while the New Amsterdam plant is referred to A. insularis Citerne
Eight subspecies of A. Sanyuisorbac are created for the Australian and Tasmanian forms, none of which extend to New Zealand. The New Zealand form [ unclear: ] , all of which are endemic, consist of the following subspecies:—
Novae-Zelandiae (Kirk) Bitter, and its varieties—vindi [ unclear: ] ssima Bitt. and subtusglaucescens Bitt.
Caesiiglauca Bitter (probably = var. pilosa T. Kick of A. Sanguisorbae) and its vars. brevibracheata Bitt. and involucrata Bitt.
Profundeincisa (described from cultivated plants) and its variety sericeinitens Bitt. (Kelly's Hill, leg. L. Cockayne).
Pusilla (described from a cultivated plant in the Bremen Botanical Garden) and its five varieties, three of which are founded on specimens in Herb. Berol., collected by Krull in Chatham Islands, and another var. antarctica Cockayne.
Aucklandica* (Auckland Island Hooker. f. Herb. Berol., Florent., Paris).
The remainder of the New Zealand species are put into two special sections of the genus, both of which are endemic, A. glabra Buchanan forming the section pteracaena Bitter, and A. microphylla Hook f. and A. Buchanani Hook f. the section microphyllae Bitter. A. microphyslla is divided into the subspecies eumicrophylla Bitt. and obscurasens Bitt. The former contains the var. inermis (Hook. f.) Kirk, and this is resolved into two forms named respectively longiscapa Bitt. and breviscapa Bitt. and the var. pallideolivacea Bitt. described from a cultivated plant in the Berlin Botanic Garden. The subspecies obscurascens is based on cultivated plants coming from the nursery of Thomas Ware; the vars. depressa T. Kirk and pauciglochidiata Bitt. are included here. This latter is evidently the dune form of Southland. A new variety inermis Bitt. of A. Buchanani is described.
Finally, a number of hybrids of garden origin, mostly between New Zealand species, especially A. microphylla and A. Sanguisorbae are described and their leaves figured.
It must be added that the author does not look upon this work as a monograph of the genus, but only as material for such
[Footnote] [* It is almost certain that this is identical with A. Sa [ unclear: ] ae var. an [ unclear: ] Cockayne. That variety was founded, so far as the description of the flower and scape went, upon one flower coming out of season on a plant just brought from Auckland Island. It-is now known that the fruiting-scape is much longer than as described, and that its hairiness was underestimated. Bitter suggests the Auckland. Island plant may be related to A. insularis.]