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Browse the 1966 Encyclopaedia of New Zealand
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Graphic: An Encyclopaedia of New Zealand 1966.

Warning

This information was published in 1966 in An Encyclopaedia of New Zealand, edited by A. H. McLintock. It has not been corrected and will not be updated.

Up-to-date information can be found elsewhere in Te Ara.

LIVERWORTS

Contents


Life-history

Both the leafy “plant” and the thalloid “plant” are the sexual or gametophyte generation of the life cycle. They both produce the sexual organs on some part of their surface. The female organs or archegonia are flask-shaped structures containing the embryo cell. In the leafy plants they are formed at the apex of a stem or branch-arresting growth. In the frondose group they are produced on or somewhat below the surface of the thallus, or on special combinations such as a stalked receptacle. The male organs are the spermatozoids, which are released from oval or globose, stalked or sessile bodies called antheridia. They may or may not be on the same plant as the archegonia. When the embryo cell is fertilised, the development of the second half of the life cycle, the sporophyte, at once begins. The basal part which penetrates the host to obtain nourishment is called the foot. The upper portion develops into a capsule, which produces spores internally. Protected usually by two envelopes, the inner one, the calyptra, being always present, the capsule ripens and erupts through the calyptra (this being the main difference from the mosses) to scatter the spores, either by splitting downwards into four valves or by bursting irregularly. In the foliose plants and Metzgeriales of the thalloids, the capsule usually possesses a delicate, elongate, hyaline stalk called the seta; as Hooker writes: “slender, white, cellular fruit-stalks, surmounted by 4 little brown radiating arms (valves) placed crosswise”. A variously shaped assemblage of cells, developed from the germinating spore, then gives rise to the gametophyte, and the cycle begins again.

Asexual reproduction by way of small detachable gemmae is commonly met with. It has even been suggested that, in course of time, gemmae may replace the sporophytes as a means of propagation.