Common name: Quillwort
Scientific name: Isoetes lacustris
Genus: Isoetes 水韭屬
Family: Isoetaceae 水韭科, quillwort family
Remarks:
Origin: native
Note: Isoetes lacustris, squillwort and Isoetes echinospora, spring quillwort looks very similar in appearance and they could occur in the same lake. They could only be distinguished accurately by microscopic examination of their megaspores.
The following individuals seems to be the former one but it needs microscopic examination to confirm its identity.
Date: 13th Aug
[177] A lot of quillworts found in shallow water of a lake. It is said that it is usually present in some quantity, forming a dense turf on deeper lake bottoms. (vs Isoetes echinospora, spring quillwort usually scattered though rarely forming continuous swards)
[174] A submerged evergreen aquatic plant. It is found in acidic, clear-water lakes from marginal shallows to about 5m. (The depth of the lake these plants were found was 3m in average.)
[181] A rosette of smooth, cylindrical, sheathing leaves.
[182] Upright, spreading clusters of more or less straight, rigid leaves emerging from a rooted 'corm'.
[180] Note that a water lobelia,
Lobelia dortmanna 水生半邊蓮
* is found left to a quillwort and a comparison could be made between their apperances, especially their leaves. (Note '水生半邊蓮 ' is not an official chinese name for this species, it is only suggested by a
Taiwanese website).
[178] Leaves erect, sometimes recurved 反曲的 (i.e. 葉端向外、向下翻卷) (vs leaves initially erect, but soon bending away from the centre of the rosette, often appressed to the substrate (looking starfish-like) in Isoetes echinospora, spring quillwort.)
[154] A detached plant near the shore of the lake.
[165] More detached plants are found.
[166] Detached leaves are found as well.
[155] Leaves somewhat brittle, remaining stiff when taken out of the water vs flaccid and clinging together when taken out of the water in Isoetes echinospora, spring quillwort.)
[164] Leaf 10-45 cm long, c. 2.5-12 mm wide, cylindrical to varying degrees. (vs leaf 3-25 cm long, c. 2.5-3 mm wide near the base, with a perceivably slightly flattened adaxial face in Isoetes echinospora, spring quillwort.)
[173] Take a detached plant from the shore to have a closer examination.
[172] The lower part of the leaves are white and a bit transparent (It is white maybe because it died for a while) . It seems there are some transverse septum found along the whole length of the leaves.
[159] Middle part of a leaf, it becomes more greenish.
[154_1] Leaf parallel-sided and tapering only slightly (abruptly tapered) in the last few centimetres towards a rather blunt asymmetrical point (vs tapering almost immediately from the base to a slender, acute apex (tapering gradually to an cute tip) in Isoetes echinospora, spring quillwort.)
[154_2] Tapering abruptly at the leaf apex.
[157]
Upright, spreading clusters of
more or less straight, rigid leaves emerging from a
rooted 'corm'.
[160] Leaf base is spoon-shaped, reviewing its true identity as a quillwort. The photo above also show the fibrous roots.
[158] Another closer examination to show the swollen leaf base.
[162] Need to peel off the outer leaf (sporophyll 孢子葉) to see the sporangium.
[162_1] Photo cropped above to show the ligule (Li), megasporangium (Mm) and megaspores (Me) found at the inner surface of leaf base.
[162_2] A much more magnified photo to show the megaspores (orange dashed line).
Megaspores 500-570 micrometres diameter, the
mature spore wall showing
anastomosing 網結的 that resemble
brain-coral ridges (x20 lens) (vs megaspores
420-450 micrometres diameter,
densely spiny on all faces (x20 lens, only seen when dry and mature, i.e. late summer and autumn) in
Isoetes echinospora, spring quillwort.)
[170] Another leaf come from a washed-up specimen.
[170_1] Cropped photo above to show the megasporangium (Mm) and megaspores (Me).
