Tuatara: Volume 9, Issue 2, November 1961
The Liverwort Genus Marchasta
The Liverwort Genus Marchasta
There are a number of genera of liverworts in which the plant body takes the form of a flat, lobed thallus with no differentiation into stem and leaves. Three of these genera are readily distinguished from the others in that on the upper surface of the young thallus there are small cups containing minute plants (gemmae) which are readily detached when mature to float away in water and grow into new plants.
Two of the genera, Marchantia and Lunularia, are world-wide in their distribution and are readily found in New Zealand. The third genus. Marchasta, has been collected only from New Zealand and from the islands of Tristan da Cunha in the South Atlantic Ocean.
Marchasta has been recorded from a number of localities in New Zealand. The type specimen was collected in kamahi-rata forest alongside the track to Alec's Knob at Waiho, South Westland.¹,² Persson described the genus, at first under the name of Hodgsonia and later as Neohodgsonia, and gives as additional localities the head of Lake Manapouri, the track from Wilmot Pass to Deep Cove in the Doubtful Sound region, and Mt. Holdsworth and Table Top in the Tararua Mountains.³
When growing under favourable conditions of high humidity and good drainage Marchasta is easily recognised as it spreads itself irregularly over an area of up to a square metre to the exclusion of all other vegetation. A typical substratum is leaf-litter amongst the exposed roots of fallen trees. The general appearance is very striking with flecks of pale green on a background of deeper green, the whole plant more delicate than a Marchantia and in some respects resembling an Asterella. The gemma-cups are distinctive, as are also the twice-bifurcated, stalked archegoniophores and shorter, flattopped antheridiophores. Some or all of these are certain to be present except in very young plants.
Marchasta clearly belongs to the order Marchantiales. The differentiation of the thallus into an upper, photosynthetic region with air chambers and a compact lower region, the presence of multicellular scales and two types of rhizoids, together with distinctive characters of the antheridium. archegonium and sporogonium, all point to this conclusion.
An eminent authority has put forward the suggestion that Marchasta may have originated by hybridization between Marchantia and Asterella. Although this is a line of thought worth critical page 79 investigation, the fact that Marchasta has a wide range within New Zealand and also extends to Tristan da Cunha would indicate that the genus has been in existence for a considerable time.
The writer would be glad to know of any additional localities in which Marchasta occurs and would be especially grateful for ripe spores in order to supply several overseas botanists who have asked for them. Dr. J. W. Dawson has already reported finding the plant at the summit of Mt. Matthews and at Ship Cove, Marlborough Sounds.
1. Campbell, Ella O., 1954. Marchasta areolata, Campbell, a new monotypic genus of the Marchantiaceae. T.R.S.N.Z. 81, 485-8.
2. Campbell, Ella O., 1954. The structure and development of Marchasta areolata, Campbell. T.R.S.N.Z. 82, 249-62.
3. Persson, H., 1954. On Neohodgsonia, H. Perss., the new hepatic genus from New Zealand and Tristan da Cunha. Bot. Not., 39-44.