Morphology, ultrastructure and typology of orbicules in Isoetes
aquatica as well as Isoetes
echinospora, occur in oligotrophic lakes.
De estas las de distribucion geografica mas amplia son Isoetes
mexicana y Oserya coulteriana (conocidas de 11 estados); por otra parte, cuatro especies endemicas se conocen como restringidas a uno solo: Eleocharis arsenifera (Chihuahua), Eleocharis reznicekii (Durango), Oserya longifolia (Jalisco) y Tagetes epapposa (Durango).
Fewer than 50 cases are known Briafrana (Isoetes
Biafrana) is only found on Mount Oku, Cameroon, & Bioke isle, the Gulf of Guinea Encephalartos altensteinii Found along the Eastern Cape, South Africa, where numbers have declined more than 30% in 50 years
Spores of Isoetes
lacustris were found at three sampling points from the eastern shore: VM38 (D 2.3 m; DS 19 m), VM49 (D 2.2 m; DS 31 m), and VM54 (D 1.35 m; DS 20 m).
The dominant species of marsh vegetation is Phragmites australis, and the companion species include Potentilla anse-rina, Salix brachypoda, Alisma plantago-aquatica, Isoetes
acustris, and Plantago asiatica.
However, like in the coverage groups, the LCB3 lakes are characterized by the lowest and the highest values also for macrophyte growth depth, which depends mainly on the presence of a moss polster, because in Estonian lakes the growth limit is mostly 2 m for Isoetes
and 1 m for Lobelia.
Rare species noted from the community are many, including buffalo clover (Trifolium reflexum--SE), eastern eulophus (Perideridia americana--SE), broom panic grass (Dichanthelium scoparium (Lam.) Gould--SE), clustered fescue (Festuca paradoxa--ST), blackfoot quillwort (Isoetes
melanopoda--ST), Wolf bluegrass (Poa wolfii--SR), rough rattlesnake root (Prenanthes aspera--SR), and Wolf spikerush (Eleocharis wolfii--SR).
Wetland or semi-aquatic plant pollen from types such as Cyperaceae (sedge f amily), Typha latifolia (cattail), Sphagnum, and Isoetes
(quillwort) are present in these samples but they are not abundant (Fig.
Macrophyte growth is sparse in all lakes with the exception of small patches of Isoetes
, Nuphar, and Sparganium.
Although this mineral content is always very low, the differences are enough to cause changes in the species composition and in the trophic stage, and thus, for example, lakes with very soft waters have communities dominated by Isoetes
. In slightly harder water, this community is replaced by a "meadow" of Potamogeton, Ceratophyllum, Myriophyllum, and water crowfoots (Ranunculus).
The main habitats are: (1) the ankle-deep bank of the shore (a bank of willow roots and moss); (2) the 1.5-3.0 m deep bed of the macrophyte, Isoetes
kirkii; and (3) the 4.0-6.0 m deep bed of an introduced species of macrophyte, Elodea canadensis ([ILLUSTRATION FOR FIGURE 1 OMITTED] in Lively and Jokela 1996).