Eleocharis mamillata subspecies mamillata

Eleocharis mamillata sensu stricto

This plant is not yet known in UK! It should be looked for anywhere, as an early colonising, but ephemeral, species.

Thomas Gregor writes (pers. comm.)
Eleocharis mamillata is not a rare plant in Central Europe. But it occurs very patchily and not for long in any one place. It is able to reach new ponds, especially those dug by nature conservation groups. It is probably transported by ducks. I would not be surprised if it turned up in England, for instance somewhere in the south. ... Eleocharis austriaca and E. mamillata produce huge amounts of seed. They do not seem to invest much energy in lasting vegetative organs. I regard them as pioneer species”.

NB: The photographs below are from specimens originating in Germany. I am very grateful to Mike Wilcox for sending material collected by Thomas Gregor. I am also grateful to the latter for exchanges on the status of this taxon.

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Studies abroad (e.g. Gregor (2003): see References, below) suggest that intermediates connect E. mamillata subspecies mamillata with subspecies austriaca, which is more characteristic of upland river-banks and ox-bow pools, very often with some calcareous influence in the water.

British plants referable to
austriaca tend towards the intermediate zone between these two in some characters, but thus far no evidence has arisen of true subspecies mamillata. Work is proceeding on UK plants.

Subspecies austriaca is distinguished by its narrower-based and taller style-base, and nut with a usual count of five bristles (six here).

Like austriaca in most features:
an often tall-stemmed plant much as austriaca (only palustris compares for height with these), but variable
stems pale green, circular in section, flimsy and brittle
epidermal peel show 'open' structure, like austriaca
basal sheaths not red/purple flushed at base (contrast palustris)
patch-forming (like palustris and uniglumis, but unlike the tufted multicaulis), or even sheet-forming
spikelets typically conical but can be ovoid (then similar to palustris)
spikelets typically many-flowered – at least 20 and often more flowers/nuts
the two basal glumes are sterile (enclosing no flower or fruit), similar in size and shape, short, and typically each encloses just half the spikelet-base with no overlap (like palustris, but contrast uniglumis)
stigma 2-forked (as in austriaca, palustris and uniglumis; contrast multicaulis and the three smaller species which are 3-forked)
ripe nut has a persistent style-base, distinctly swollen (more so than austriaca), and constricted at the attachment to the nut with a 'neck' (wide as in palustris, multicaulis, and uniglumis, but lower in height than these; contrast quinqueflora and the smaller species which have the style-base confluent with the nut)
nut has usually six bristles at its base, less often five (typical for austriaca) or other counts
usually emergent from shallow or deeper water, often from silt over a gravelly substrate; characteristic of artificial ponds, usually with base-poor waters

Stem sections
see the page ID:palustris/austriaca for discussion.

stem sections (from dried specimen: not recovered circular shape)

very like austriaca: perhaps even more ‘open’. Note well-separated fibre-bundles with wide strips of epidermal cells in 3-7 ranks. It is this relative lack of fibre-bundles that makes the stems britlle rather than flexuous.
(See ID:palustris/austriaca for discussion.)

epidermal peel

like austriaca, generally shorter than in palustris ssp. vulgaris; mean 58 μm (n=20) in this specimen
guard cells protrude beyond the subsidiary cells (as in austriaca, unlike palustris), (“like a hot-dog”)

stomata have the guard cells protruding (like austriaca, unlike palustris)

stigma 2-forked
perianth bristles usually 6.

style-base (stylopodium) is persistent, and strongly swollen, but lower in profile than in palustris (and the other larger species)
style-base has a constriction (‘neck’) at its junction with the nut
vs. austriaca: much more reminiscent of palustris ssp. vulgaris

ripe nuts showing swollen style-base with strongly-constricted ‘neck’,
perianth bristles (with downcurved hooks), and persistent filaments

Standhede & Dahlgren (1968) say “small stagnant ponds etc. without competing vegetation in +/- oligotrophic, non-calcareous areas”. See also Thomas Gregor's comments at the top of the page.

Frequency & range
not known in UK; local in central and northern Europe
rather ephemeral; an early colonist and poor competitor: readily eliminated as pools become overgrown

Gregor, Thomas (2003)
Eleocharis mamillata – Distribution and Infraspecific Differentiation (Folia Geobotanica 38: 49–64).
This can be downloaded from the following link, under the heading '2003':

Strandhede, Sven-Olov (1966) Morphologic Variation and Taxonomy in European
Eleocharis, Subser. Palustres. (Opera Botanica 10:2; 1-188).
This can be ordered from:

Strandhede, S-O & Dahlgren, R. (1968) Drawings of Scandinavian Plants 9-10. (Botaniska Notiser 121-1, pp. 1-10).
[I have not found a source for this.]

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Eleocharis spike-rush pages (also accessible from the sidebar)