Takakia (Takakia)
Description
Takakia is not only unusual among mosses, but among all living plants. The plant's Japanese name (nanjamonja-goke) "impossible moss" reflects this. It was believed to have the lowest known chromosome count (n=4) per cell of any land plant., but some plants of the small Australian daisy Brachyscome dichromosomatica are now known to have a count of n=2. From a distance, Takakia looks like a typical layer of moss or green algae on the rock where it grows. On closer inspection, tiny shoots of Takakia grow from a turf of slender, creeping rhizomes. The green shoots which grow up from the turf are seldom taller than 1 cm, and bear an irregular arrangement of short, finger-like leaves (1 mm long). These leaves are deeply divided into two or more filaments, a characteristic not found in any other moss. Both the green shoots and their leaves are very brittle. Unlike in other bryophytes, the egg-producing archegonia and sperm-producing antheridia are not surrounded by perichaetial leaves or other protective tissues. Instead, the gametangia are naked in the angle formed between the stem and the vegetative leaves. The sporophyte develops a long stalk ending in an elongated spore capsule. The capsule contains a central columella over and around which the spores are produced. When the sporophyte is mature, the capsule ruptures along a single spiral slit to release the spores.
Taxonomic tree
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Domain: Eukarya
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Kingdom: Plantae
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Phylum: Bryophyta
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Class: Takakiopsida
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Order: Takakiales
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Family: Takakiaceae
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Genus: Takakia
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