Lastreopsis

Primary tabs

Lastreopsis

Description

hairs almost always present on both surfaces of axes and often on lamina, always consisting of several cells, in some species acute, remaining stiff when dried, in other species not acute and becoming contorted when dried;

Distribution

Australasia: present Pantropic: present
Pantropic; about 35 species, most abundant in Australasia.

Taxonomy

In his Index Filicum (1905) Christensen included all species of Lastreopsis, as here delimited, in the genus Dryopteris which he recognized as being a complex, for which he proposed a tentative subdivision on pp. xx- xxii. In attempting a better subdivision, in his Monograph of Dryopteris (1913 and 1920), he limited himself to the species of tropical America. R. C. Ching spent three years (1929-1932) in Europe, studying ferns with Christensen and visiting the major European herbaria to see the types of Chinese species. He attempted to apply the ideas expressed in Christensen’s Monograph to the species of Asia. In so doing he recognized that in Asia there is more than one group of species which accord with Christensen’s definition of Dryopteris subg. Ctenuis. One such group he separated under the name Lastreopsis (1938) noting that the hairs on the frond are not contorted when dried; he included only four species (one of them is here excluded). In a new classification of Leptosporangiate ferns (1940) he raised Dryopteris subg. Parapolystichum (Keyserl.) C. Chr. to generic rank, placing it, without discussion, in the family Thelypteridaceae, evidently because the hairs are different from those in his Las- treopsis, though they are quite different from the hairs shown by Christensen to be characteristic of Thelypteris. Ching added two species of the Pacific to those of tropical America included by Christensen in his subgenus.

Dr M. D. Tindale published an account of the Australian species of Lastreopsis in 1957. Then, looking more widely, she discovered that there are species of Lastreopsis in Africa and America and prepared a full monograph of the genus (1965) recognizing 33 species. In so doing she redefined the genus and concluded that it comprises species with different types of hairs, including those placed in Parapolystichum by Ching. With this conclusion I agree. As an indication of past confusion, it is notable that synonyms in 14 different genera are recorded by Tindale.

Lastreopsis accords with Ctenitis in the presence of glands on various parts of the frond, on indusia and on the stalks of sporangia. It differs from Ctenitis in scales, in the shape of axes of the frond in relation to the leaflets they bear (not noticed by Ching) and in the position of linear aerophores on stipe and rachis (mentioned by neither Ching nor Tin- dale). In scales Lastreopsis is nearer to Tectaria than to Ctenitis.

Cytology

Base chromosome number 41; Malesian species L. rufescens and L. tenera diploid; some Australian species tetraploid.

Citation

R. C. Ching - in Contr. New South Wales Natl. Herb. 1965: 249
M. D. Tindale - in Victoria Naturalist. 1957: 180