Under & Verboom, Generic limits in the Rytidosperma complex 
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(d) a base chromosome number of h = 5 (if correct) as insufficiently differentiating 
characters. Jacobs (1982) added (e) the absence of abaxia! microhairs and (f) circular 
silica bodies, and argued for the retention of the genus. 
Several of the characters suggested by Veldkamp and Jacobs are more widespread in 
Rx/tidosperma, even if in less developed form. Reduction in the inflorescence forms a 
continuum, and the development of spike-like inflorescences has also occurred several 
times. The development of a bidentate and aristate, or even an acute lemma apex, 
appears to be the consequence of the fusion of the lemma lobes to the awn column. 
Intermediate forms of fusion are common in this clade, and similar fusion patterns 
have been observed in the African genera TriboUum and Prioxxanthiuw. Detailed 
observations of the lemma vasculature further corroborate the derivation of bidentate 
lemmas in this group from a bilobed lemma. Awn reduction is more complex, in some 
groups the column is lost, leaving only the apical setum (e.g. in TriboUum and 
Mouostachxja), in others the strap-like column is retained, which may show some twisting 
(e.g. Plinfhaiithesis). Cushion-like growth-forms also appear to occur in some New 
Zealand species of sect. Buchaxmnia. The reported base chromosome number (2fi = 10) 
of R. oreoboloides is unusual for the clade, and requires corroboration. The anatomical 
peculiarities (absence of abaxial microhairs and shape of the silica bodies) are also 
more widespread in Rytidosperma s.s. (see Table 1), and may even be found in some 
South American species (Tomlinson 1985). These character distribution patterns are 
matched by the gradual reduction in the lemma indumentum, culminating in several 
species with glabrous abaxial lemma surfaces. As noted by Jacobs (1982), Monostachya 
is indeed a distinct group; however, it is embedded in the Rytidosperma s.s. clade, and 
many of the peculiarities of the high altitude New Guinean species may be regarded 
as specialisations to the anomalous tropic alpine environment. Recognition of 
Monostachya would firstly require some indication of the degree of inclusiveness of the 
group, but essentially the whole of the Rytidosperma s.s. clade would have to be included 
in order to delimit monophyletic taxa. Monostachya, as delimited by Jacobs (1982), 
renders Rytidosperma paraphyletic. 
Erythranthera was described by Zotov (1963), distinguished by the minutely three¬ 
toothed, awnless lemma, and a long bare rachilla internode associated with a short 
callus borne at right angles to the internode. This genus includes two rare species, 
which are found in long-lying snow-drifts. 
Pyrrhanthera is a monotypic genus from New Zealand, separated by Zotov (1963). It 
has a unique growth-form in the Rytidosperma group, with long, spreading rhizomes, 
and very sparsely flowering aerial shoots. In addition, the fruit is a nutlet, with a 
separable wall. 
Blake (1972) accepted Erijthranthera without any critical discussion; Tomlinson (1985) 
does not pronounce on the desirability or otherwise of recognising these genera, 
commenting merely that the leaf anatomy does not support them, but that glabrous 
lodicules are indeed rare in Rytidosperma. Clayton and Renvoize (1986) recognise 
only Pyrrhanthera, presumably due to the fruit. Both genera have unique characters, 
which constitute the basis on which they were recognised. The three species in these 
two genera, like those included by Jacobs in Monostachya, are indeed peculiar. 
However, they share the leaf anatomy and basic spikelet morphology of the 
Rytidosperma s.s. clade, and may represent specialisations from this basic condition. 
As with Monostachya, recognising them would result in a paraphyletic Rytidosperma, 
consequently we suggest including them in Rytidosperma. They appear to represent 
specialisation to peculiar habitats. Erythranthera is usually found in snow-hollows, 
both in Australia and in New Zealand. Pyrrhanthera is found in arid plains on the lee 
of the New Zealand alps. 
