Abstracts. 57 



but also mesothermous, and the latter boreal, but endowed with a strong power of 

 expansion. Gleichenia is abundant in Tertiary rocks of Europe in its subgenera 

 Mertensia and Eugleichenia, but the ice age drove it far to the south. The retreat 

 of a Tertiary genus into the far oceanic south, with its insular climate, and into the 

 tropical mountains, is most remarkable. 



The author divides the earth, so far as ferns are concerned, into twelve floral 

 regions, of which the Australian New Zealand is one. The latter includes the 

 rain-forest region of eastern Australia, Tasmania, and New Zealand. Central 

 Australia is of no moment for ferns, and northern Australia comes into the Malayan 

 region. The boundary between the two fern floras extends from King Sound along 

 the north coast to the east coast, and thence through Queensland to the tropic of 

 Capricorn, beyond which, southwards, the Malayan element gradually fades away. 



As for New Zealand, to quote the author's words, "The fern-world is not only 

 one of the most luxuriant and largest, but floristically one of the most interesting. 

 Tt is a little world of ferns in itself, where almost all the genera of tropical and 

 temperate ferns are to be found." A brief review of the species and genera is 

 given, and their most important growth-forms; the presence of an endemic species 

 of the tropical genus Lygodium is considered very remarkable. The author con- 

 cludes : "It would be profitable to stay longer with this magnificent flora, which, 

 though it is not the expression of a maximum hygrothermous forest climate, is 

 easily the ideal fern climate of the present day, and plainly shows the optimum 

 average conditions for the well-being of ferns." 



The interesting question of the circumpolar extension of the Australian-New 

 Zealand fern flora is discussed. The special group which ma}', in a certain sense, 

 be called "antarctic" is not at all of a boreal-arctic character, but rather of a 

 temperate to a subtropical character. Neither are the species analogous with either 

 arctic phanerogams or even antarctic with the highly characteristic cushion form 

 of these latter. First come six species of Bhchnum, two of Polystichum, two of 

 Polypodium, Hymenophyllum ferrugineum,, Asplenium obtusatum,, and Schizo' u 

 fistulosa. Also Todaea comes here, with its distribution in Australia, New Zealand, 

 and South Africa. All the above are common to Australia - New Zealand, South 

 America with Juan Fernandez, and in part South Africa. H'ypolepis ruguloaa juay 

 be also included (New Zealand, Reunion, Tristan d'Acunha, St. Helena, Juan 

 Fernandez). The genus Dirhsonia in closely related species extends from the Aus- 

 tralasian floral region to oceanic Malaya, Juan Fernandez, and St. Helena. Then 

 there is Schizaea, the most scattered, however, of all these genera. 



The distribution of the above species may be explained on the supposition of a 

 Tertiary or yet older region lying in the far south, whence they, in common with 

 so many flowering-plants of the same area, extended radially. That the region 

 in question was both ancient and warm is proved by the frondose structure and 

 stems of the larger and the delicacy of the smaller ferns, Schizaea of Juncus form 

 excepted. This element is a relic of a more extensive southern flora which dates 

 from the Tertiary, or earlier, and which now remains on its small New Zealand- 

 Australian area, thanks to the climatic conditions persisting that it requires. 

 Further, in discussing the origin of the antarctic element of the south Chilian 

 flora the author brings more facts in favour of an antarctic Tertiary centre of 

 distribution, which is supported, moreover, by the additional fact of the presence 

 of several Tertiary fossil ferns from Seymour Island which are related to, if not 

 identical in some cases with. South American species. 



L. C 



5. Die Gattung Acaena. By G. Bitter. (Bibliotheca Botanica, Heft 74, 

 pp. 336, pi. 38, figs. 98. Stuttgart, 1910-11.) 



This voluminous 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 ova'li folia E. 

 and Pav. in the botanic garden of Christiania, and the plant is described as subsp. 

 glabricaitlis ; 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. 



