The hepatic , Jensenia sprnosa ( = PaUavicinia stephanii : Pallaviciniaceae ) , in southern Africa

Recently, specimens ot Jensenia spinosa (= PaUavicinia stephanii) were collected at the type locality ‘Spitskop. bei Lydenburg , in the Transvaal. The type, which previously was the only specimen from southern Africa, is held” at G. A detailed description of J. spinosa. illustrated with photographs of the thalli and spores is presented here, since earlier descriptions are sketchy and lack illustrations.


INTRODUCTION
The subfamily Pallavicinioideae (Migula) Grolle of the family Pallaviciniaceae Migula, order Metzgeriales, com prises the genera PaUavicinia and Jensenia (see below).Jensenia Lindb.( 1868) is the older name for the latter of the two genera and had to replace Makednothallus Verdoom (1932) (Grolle 1964), which was based on Mittenia Gott.(1864).This name, however, was taken up already by Mittenia Lindb.(1863), a genus of mosses.Jensenia was treated by Schiffner (1893) and later authors such as Schuster & Inoue (1975); Grolle (1984); Grolle & Piippo (1984) and Schuster (1992), not as a genus, but as a sub genus of PaUavicinia.It corresponds to Stephani's (1900) PaUavicinia sectio Dendroideae.Differences between Jensenia and PaUavicinia are shown in Table 1.Grolle & Piippo (1986) list several of the above dif ferences to demonstrate that Jensenia is a natural group which they prefer to treat at the generic level.I have fol lowed them in this study even though Schuster (1992) adopts a broadened concept of PaUavicinia to include Jensenia because of the following: in PaUavicinia levieri Schiffn. the androecia have scales scattered over the costal surface in several poorly demarcated rows, i.e. more like those in Jensenia (or Mittenia, as Schuster prefers to call it.since Mittenia has priority at subgeneric rank).Further more, in the Japanese PaUavicinia longispina Steph., Schuster (1992) often found a basal stipe that was creeping and rhizoidal, contrasted to an ascending (but not erect) frond, that was 1 or 2 (very rarely 3) times dichotomous, i.e. also as in Jensenia, as opposed to PaUavicinia which is supposedly always prostrate and without a creeping rhi zome.The differences between PaUavicinia and Jensenia are therefore not clear-cut in the above two characters, but in the remaining ones (see Table 1), the differences are deemed to be sufficiently marked to treat Jensenia as a separate genus, rather than as a subgenus of PaUavicinia.Six species (Grolle 1964) or seven (Engel 1990), are clas sified in Jensenia, which belongs to a southern and prob ably Gondwanaland element.Jensenia spinosa (= PaUavicinia stephanii; = Makednothallus stephanii) is the only African representative.Initially Grolle (1965) had not recognized the combination Makednothallus stephanii (Jack) Schust.(Schuster 1963) and Jones (1990) made the combination Jensenia stephanii (Jack) Jones.The type specimen of PaUavicinia stephanii was collected by Wilms at Spitskop. 'bei Lydenburg'. Transvaal, in 1888.This collection is held at G. No specimens of J. spinosa were housed at PRE. except for the recent acquisition of a De Sloover collection from Rwanda, through the kind ness of Dr Riclef Grolle. Amell (1963) admits that he did not see examples of this taxon himself, but based his de scription on that of Stephani.Two recent attempts were made to collect this species again at a locality called Spitskop.situated south of Lydenburg.but were unsuc cessful.Only upon coming across a copy of Wilms's (1898) 'Ein botanischer Ausflug ins Boerenland' did it be come clear that the Spitskop to which he referred, lay about 50 km east of Lydenburg and 9 km south of the present town of Sabie.which was only proclaimed later.Fresh material of this locally scarce species was recently collected within sight of this Spitskop.on the protected vertical banks of a small streamlet, close to the water sur face.Jensenia spinosa and its spores are herewith de scribed in detail and illustrated with photographs, as earlier descriptions are sketchy and not illustrated.
Besides the type locality in southern Africa (Figure 5), J. spinosa is known elsewhere in Africa from Malawi, Tanzania.Rwanda and Zaire, as well as from the islands Mauritius, Reunion and St Helena (Grolle 1979), gener ally from high elevations.Vana et al. (1979) reported it as Pallavicinia stephanii from Rwanda and Reunion.It is therefore quite widespread, but scarce.
According to Grolle (1979) J. spinosa is very similar to the neotropical species, J. erythropus (Gott.)Grolle;Schuster (1992) concludes that in the description and illustrations of J. erythropus by Hassel de Menendez (1961), the scales are scattered over the dilated sectors of the frond segments.The only other dendroid member of the family Pallaviciniaceae in Africa, is Symphyogyna podophylla (Thunb.)Mont.& Nees (Perold 1993) which, in the absence of female material, is quite difficult to dis tinguish from J. spinosa.Grolle (1979) gives a key to distinguish them (on vegetative characters), in which he draws attention to the smaller, as measured by him.21-27 x 24-35(42) (im, inframarginal cells of the thallus wings with the cuticle finely punctate to striate in J. spinosa, whereas in S. podophylla he found these cells to be larger at 50-60(65) x 50-75 Jim and the cuticle smooth.Van der Gronde (1980), who studied the genus Jensenia in Colombia, states that female material of Jensenia is neces sary to distinguish it with certainty from a dendroid Sym phyogyna, which has a scale-like involucre and lacks a pseudoperianth.In Jensenia the involucre is cup-like and, after fertilization, a long pseudoperianth develops; the lat ter is joined with the calyptra at the base.There are thus three structures surrounding the sporophyte in Jensenia: the involucre, the pseudoperianth and the calyptra.

FIGURE 1
FIGURE 1 Jensenia spinosa.LM photographs of thalli.A. terminal branching; B. single branch with toothed margin; C, ts.o f branch showing costa with central strand and lateral wings; D. ts. of rhizome; E, ts. of branch; F. small, remote teeth at margin; G. ts. of costa and central strand; H. ts. of apical part of stipe with double conducting strand, note also 2-celled slime-papilla; I. cells containing oil bodies and chloroplasts; J, cells along margin of branch: K. cells in lamina; L. dorsal cells over costa.A-C.Wilms 007W 4\ D -L Perold Koekem oer 2923.A, x 7.5; B. x 25; C. x 125; D. H. x 50; F. x 100; G. J-L.x 250; I. x 500.
FIGURE 5.-Known distribution of Jensenia spinosa in southern Africa.