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Volume IV (1988) - Flora of New Zealand Naturalised Pteridophytes, Gymnosperms, Dicotyledons
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Polystichum Roth

POLYSTICHUM Roth

Terrestrial ferns. Rhizomes erect, very scaly. Fronds 1-3-pinnate, scaly; ultimate segments usually pointed; veins free. Sori round, borne on veins in one row either side of midrib; protected by peltate indusia, or indusia 0. Spores monolete.

Key

1
Fronds bearing bulbils
2
Fronds lacking bulbils
4
2
Fronds with numerous bulbils, borne along rachises at junctions with pinnae
2. *setiferum
Fronds with 1 or a few bulbils only, borne near apices of rachises (rarely at apices of primary pinnae)
3
3
Basal primary pinnae bearing stalked secondary pinnae
1. *proliferum
Basal primary pinnae incised, sometimes to midribs, but never bearing more than 1 stalked secondary pinna
*lentum ζ
4
Indusia with conspicuous black centres; stipe and rachis scales with colourless fimbriate bases
4. richardii
Indusia uniformly pale brown or 0; stipe and rachis scales with entire margins, usually lacking fimbriate bases (except Ch. plants of P. vestitum)
5
5
Stipe and rachis scales uniformly pale orange-brown; indusia markedly convex; plants alpine
3. cystostegia
Stipe and rachis scales with shiny dark centres and broad pale margins; indusia flat or 0; plants lowland or montane
6
6
Indusia 0; midribs of primary pinnae with narrow wings
5. silvaticum
Indusia present; midribs of primary pinnae usually lacking wings
6. vestitum

c. 150 spp., cosmopolitan. Native spp. 4, naturalised 3.

Polystichum is closely related to the large, predominantly N. Hemisphere genus, Dryopteris, but can be distinguished by its peltate rather than reniform indusia. The limits of these and other genera in the Dryopteridaceae are discussed by Sledge, W. A., Bot. Jour. Linn. Soc. 67, Suppl. 1 : 203-210 (1973).

Throughout the world, Polystichum spp. are difficult to define and are often poorly known because of their morphological variability, their capacity to hybridise, and their variation in chromosome number. The N.Z. native spp. are all believed to be tetraploid; P. richardii and P. vestitum are very polymorphic, and all 4 spp. are known to hybridise at least to some extent. Fortuitously, the 3 naturalised spp. can be recognised easily by their habit of producing bulbils (Fig. 5). None of the naturalised spp. are widespread.

Fig. 5. Polystichum. A-B P. lentum, A frond apex, B indusium; C P. setiferum, frond apex; D P. proliferum, frond apex. © All rights reserved. [Image: 4X59]
Fig. 5. Polystichum. A-B P. lentum, A frond apex, B indusium; C P. setiferum, frond apex; D P. proliferum, frond apex. © All rights reserved. [Image: 4X59]
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