In creek-beds and ravines in forested areas in New Zealand one is likely to find a very large liverwort, Monoclea forsteri. Hook., spreading over banks and stones in extensive mats. From its size alone it is easily recognised, its only competitor in this field being some forms of Marchantia berteroana L.&L. It occurs also in Central and South America, having been reported from Jamaica, Guadeloupe, Puerto Rico, Costa Rica, Guatemala, Venezuela, Peru, Bolivia, Argentine, Chile and Juan Fernandez (Menendez, 1957). Stephani recorded Monoclea, somewhat doubtfully, from Japan but in a personal communication Dr. Hiroshi Inoue assures me that Monoclea does not occur either in that country or in adjacent regions.

It is interesting to note that in the Argentine Monoclea is associated with Dumortiera hirsuta (Sw.) Nees (Menendez, 1957), for Hooker has recorded Dumortiera as being present in New Zealand (Hooker, 1867). However, the plant to which Hooker refers is almost certainly Monoclea as there is no other known record of the occurrence of Dumortiera in New Zealand. Hooker states ‘One of the largest and commonest Hepaticae in New Zealand, but never found in fruit and hence doubtful as to genus and species’.

The form of Monoclea found in Central America and the northern part of South America has sometimes been named M. gottschei Lindb. When growing in cultivation alongside M. forsteri from New Zealand it appears as a more delicate and slender plant of a page 17

Plate I, Monoclea forsteri Hook., the New Zealand species. Male (right) and female plants; about 1 1/2 times natural size. 1, Sporophytes: the uppermost capsule is mature and the one beneath has begun to dehisce. Below them is a capsule which has completed dehiscence. 2, To the immediate right of the number is the entrance to a flask-shaped archegonial cavity. 3, Above the number, two unopened capsules are emerging from an archegonial cavity. 4, Above the number is an antheridial cushion.

page 18 true green colour, but otherwise closely similar. However, further taxonomic work on the American plants is needed. It would be interesting to know the range of variation of Monoclea as it occurs in America.

The thallus of Monoclea forsteri is dark green or olive green in colour, branching dichotomously and becoming irregularly lobed as it spreads outwards. Where the plants grow in deep shade or are liable to flooding they are sterile, but in areas of better lighting fertile plants are abundant and in these all stages of reproduction can be found at any time of the year. The male plants are recognisable by the antheridial receptacles which appear dorsally as flat cushions on the median line of the thallus (Fig. 1). Each receptacle has some 25-30 antheridia individually sunken in flask-shaped cavities which open to the surface by a pore. The female plants have at the mid-point of each lobe a flask-shaped cavity opening dorsally by a narrow pore and containing, at first archegonia, and later 1-4 sporophytes which project from the pore as the spores ripen (Fig. 2). The capsule opens on a dry day by a single longitudinal slit on the ventral surface, the two edges curving backwards as the spores are shed (Campbell, 1954).

Figure 1. Monoclea forsteri Hook. On left, portion of a male plant, X 1. On right, portion of a female plant, × 1.

The systematic position of Monoclea is not readily determined. It shows points of resemblance to several orders of the liverworts as well as having distinctive features of its own. Monoclea resembles Jungermanniales in thallus structure and lack of ventral scales. It resembles Marchantiales in the type of oil bodies in the thallus, in the possession of two types of rhizoids and of a six-rowed page 19 archegonial neck, as well as in the form of the male receptacle and in the development of the antheridium. It resembles Calobryales in the very long, twisted neck of the archegonium, in the developmental stages of the archegonium and in the general appearance of the sporophyte. In one species of Calobryum, C. blumei, the capsule opens by a single slit as in Monoclea. The network pattern of thickening on cells of the capsule wall and the early development of the embryo are features peculiar to Monoclea. Possibly the study of fossil liverworts which are gradually becoming better known may help in elucidating relationships. In the meantime following Smith (1955) Monoclea can be placed in a monogeneric family, Monocleaceae, of the Marchantiales.

Dr. J. Proskauer in a personal communication assures me that after study of living material he considers there are no differences between Monoclea from Central Chile and from New Zealand.