The annual meeting was held on the weekend of 20-21 October in the Department of Biology at the University of Keele, by permission of Professor A. R. Gemmell. About fifty members attended and on the first day listened to six papers which are here summarized.
Dr M. E. Newton: ‘The cytology of bryophytes’.
Because of the great variety of chromosome numbers which typify families, genera and occasionally species, cyto-taxonomic data on mosses are extensive. Most work has been done on meiotic cells since chromosome counts from spore mother cells are obtained with comparative ease, but exclusive reliance on meiosis has disadvantages in cytological comparison of entire floras. Thus, chromosome number distribution could be biased by geographical variation in the incidence of fruiting arising from a preponderance of certain families or orders in a flora, or from variation in reproductive behaviour. But mitotic studies render moss cytology independent of sexual reproduction and many cyto-taxonomic features are equally discernible during meiosis and mitosis.
The diagnostic use of chromosome numbers is to be avoided at specific level because they cannot conveniently be obtained for every moss determination and because intra-specific aneuploidy and polyploidy are common. As a guide to the taxonomist in constructing or confirming taxa, however, chromosome information can be invaluable, as shown by the genus Brachythecium on South Georgia.
Liverwort cyto-taxonomy, based on mitosis is useful only at or above family level due to the restricted range of chromosome numbers. Aneuploidy in the Porellaceae is a rare exception to this. Attempts to define karyotypes in terms of V (meta- and sub-metacentric) and J (aero- and telocentric) chromosomes are too vague for taxonomic work and a return to precise measurement of chromosomes is advocated to increase the taxonomic value of liverwort cytology. Species of Pellia give some indication of this potential at the specific level.
Mr A. Eddy: ‘Aspects of Sphagnum evolution’.
In the absence of fossil gametophytes suggested lines of Sphagnum evolution must be based on comparative studies on extant forms. The lines of development proposed here involve the usual assumption that modified forms are advanced and unmodified forms are primitive. The majority of physical modifications of the gametophyte are adaptations to degree of exposure, particularly with regard to water economy. Such adaptations may be accompanied by biochemical changes as the work of R. S. Clymo and others has shown. Evolutionary trends in various structural features are outlined below.
|Branch leaves monomorphic||Branches dimorphic|
|Stem and branch leaves similar||Stem and branch leaves different|
|Cortical leuocysts poorly differentiated or narrow.
Pores single or numerous, small, random or serial
|Multi-layered cortex of inflated leucocysts. Pores confined to cell angles|
|Leaf apex intact||Leaf apex resorbed|
|Chlorocysts rectangular in transverse section, widely exposed on both leaf surfaces||Chlorocysts strongly displaced to one leaf surface or enclosed in leaf tissues|
The nearest approach to the primitive Sphagnum among extant taxa is to be found in members of section Subsecundum (S. ovatum, S. luzonense) and the stenotypic S. sericeum. The most evolved species are in sections Sphagnum (= Inophloea), Acutifolia and Rigida. Significantly, the most primitive species seem to be palaeotropical relicts, while advanced species are abundant in fairly exposed regions at high latitudes.
Professor P. W. Richards: ‘Hedw. and Schp. – biographical notes on Johann Hedwig and Wilhelm Philipp Schimper’.
Hedwig (1730-1799) is probably best known for his Species Muscorum (1801) published after his death by his successor C. F. Schwaegrichen. Though this was a landmark in moss taxonomy and has been adopted as the starting point of moss nomenclature, it was not as important a contribution to bryology as his demonstration that the antheridia were the male organs of mosses (not the spore capsules as was currently believed). This discovery prepared the way for a full understanding of the life history which was completed by the work of Hofmeister some 80 years later.
Hedwig was born in a German ‘colony’ in Transylvania but spent most of his life in and near Leipzig, where he worked as a physician, but from 1786 also as a professor of Botany. He was handicapped at first by poverty and by lack of books and instruments, but his success depended largely on the skilful use of a compound microscope which J. G. Koehler gave him, and on his accurate drawing (self-taught at the age of forty).
W. P. Schimper (1808-1880) was the son of an Alsatian pastor. He had an uneventful life, though the war of 1870 faced him with the painful choice of accepting a chair in the new German university or moving to Paris. His most important work in bryology was the Bryologia Europaea. to which he contributed much more than his two co-authors, but he also did important geological work. He was extremely industrious and covered a vast field, but was a supremely competent observer and describer rather than an originator of new ideas.
Mr S. R. Gradstein: ‘A new look at the taxonomy of holostipous Lejeuneaceae (Ptychanthoideae Mizut.)’.
Some results were presented of a study of the concept of genus and generic affinities within the subfam. Ptychanthoideae Mizut., commonly known as holostipous Lejeuneaceae. This group comprises about twenty genera with probably less than 200 species, occurring mainly in the tropics in epiphytic habitats. Marchesinia mackaii is the only European representative of this group.
It appeared that six characters are of general importance for circumscribing and grouping the genera: presence or absence of innovations, structure of the perianth, stem anatomy, oil body type, morphology of the male bracts, and cell wall thickening pattern. The last two characters apparently have not been employed before in this context.
The cell wall thickening pattern provides a basis for distinguishing two groups within the subfamily. (1) Ptychanthus group having basically cordate (asymmetrical) trigones, and comprising (a) Ptychanthus, Thysananthus, Masligolejeunea and Schiffneriolejeunea with segmented oil bodies and evolved male bracts, and (b) Acrolejeunea, Brachiolejeunea and possibly Dicranolejeunea with homogene oil bodies and simple male bracts. (2) Archilejeunea group having basically triangular (symmetrical) trigones which tend to radiate along the cell walls, and comprising Lopholejeunea, Marchesinia, Symiezidium, Archilejeunea, Spruceanthus and Tuzibeanthus.
Caudilejeunea as defined at the moment has an affinity with both groups; the position of this and some other holostipous genera such as Bryopteris, Omphalanthus and Stictolejeunea needs to be reconsidered.
Dr. J. G. Duckett and Dr. A. S. K. Prasad: ‘Ultrastructural studies on the Nostoc colonies associated with Blasia pusilla and Anthoceros spp.’
A comparative ultrastructural study has been made of the Nostoc colonies associated with the thalli of Anthoceros laevis, A. husnotii, A. punctatus and Blasia pusilla and also of the Nostoc isolated from these bryophytes and thriving in axenic cultures. Both within thalli and in axenic culture, the Nostoc cells from all four bryophytes show the same general cytological characteristics. The vegetative Nostoc cells possess extensive photosynthetic lamellar systems. Structured granules and polyhedral bodies are also consistently present. Terminal and intercalary heterocysts together constitute approximately 5% of the algal cell populations both within the bryophyte thalli and in culture. Mucilage sheaths around the Nostoc cells are less well developed in the thalli than in culture.
In contrast to this uniformity in the Nostoc, striking differences occur between Blasia and Anthoceros in the structure of the bryophyte cells associated with the alga. These cells in Anthoceros are thin walled and highly vacuolate. Mitochondria are sparse and the plastids lack pyrenoids and well-developed thylakoid systems. Nostoc filaments frequently occupy cells in which the cytoplasm is completely disorganized. However, in Blasia this latter phenomenon has not been observed. Here, the liverwort filaments growing among the Nostoc colonies are thick walled. Their inner walls possess conspicuous ingrowths whose outline is closely followed by the cell membrane. The cytoplasm contains abundant endoplasmic reticulum and free ribosomes, numerous mitochondria and proplastids. Together, these features are characteristic of transfer cells which have not hitherto been described in association with blue-green algae. The increase in the surface area of the cell membrane brought about by the ingrowths may be an adaptation which facilitates the absorption of Nostoc metabolites and particularly fixed nitrogen (as has previously been demonstrated by tracer studies) by Blasia. Thus, these cytological observations indicate that Blasia receives some direct advantage from its blue-green algal colonies while Nostoc would appear to be the main beneficiary in its association with Anthoceros.
Dr. G. C. G. Argent: ‘Bryophytes of Papua New Guinea’.
Papua New Guinea is the eastern part of one of the largest non-continental islands. It lies within the heavy-precipitation, humid tropical belt just north of Australia and is extremely mountainous with peaks rising to over 4270 m. (14,000 ft). The heavy rainfall, diverse terrain, generally low population density and geographical position make it one of the richest botanical hunting grounds in the world. Over 850 species of mosses have been recorded from this area and the proportion of endemism is very high, possibly about a third of the total number of species. Recent literature indicates that many new bryophyte species await description although a fair number of existing names must eventually become synonyms. The greater part of the flora shows Indo-Malayan affinities (although the montane element also shows links with New Caledonia and New Zealand) as well as some familiar cosmopolitan species such as Rhacomitrium lanuginosum and Funaria hygrometrica, and some highly disjunct occurrences such as Acrocladium sarmentosum and Scorpidium turgescens.
Descriptions were given of some lowland localities and the paucity of species in these sites, particularly the lack of ephemerals, was commented on. Visits to such rich localities as Mt Wilhelm, Mt Piora, Mt Sarawaket and Mt Shungol were described and the bryological interest of some of the head dresses of dancers in the highland shows was noted.
|The Annual General Meeting was held after tea and in the evening the following exhibits were shown at a conversazione:|
|Dr. G. C. G. Argent:||‘Some New Guinea bryophytes’.|
|Mr A. Eddy:||‘Aspects of Sphagnum evolution’.|
|Mr M. V. Fletcher:||‘Baked bryophytes’.|
|Mr S. R. Gradstein:||‘Genera of holostipous Lejeuneaceae (Ptychanthoideae).|
|Dr. E. W. Jones:||‘Gemmae in Diplasiolejeunea‘.|
|Dr. M. C. F. Proctor:||‘Further work on desiccation and temperature responses of bryophytes’.|
|Prof. P. W. Richards:||‘Books by Hedwig and Schimper’.|
|Mr. A. R. Perry:||‘The spread of two mosses introduced into the British Isles –
Campylopus introflexus and Orthodontium lineare‘.
All the localities visited on the excursion on 21 October were in v.-c. 39. About twenty-five members led by Mr A. R. Perry went to Anglesea Coppice, known locally as Chartley Moss (G.R. 43/0228). The Moss is a very deep bog with frequent open lawns of Sphagnum. Its drier edges are wooded, but the epiphytic bryophyte flora is poor. Noteworthy finds during the morning were Acrocladium stramineum, Campylopus introflexus* (on a rotting stump), Dicranum strictum, Ephemerum serratum var. minutissimum, Plagiothecium ruthei* (on damp soil at the edge of a pond) and Calypogeia sphagnicola* (mixed with Sphagnum magellanicum). Bryum ruderale* was found on the roadside near Chartley Castle. After lunch the party visited Dimmings Dale (G.R. 43/0543) to explore a wooded, north-facing hillside with outcropping old red sandstone. Interesting bryophytes noted were: Cratoneuron filicinum var. fallax, Dicranum strictum (in large quantities on walls and tree trunks), Oligotrichum hercynicum, Schistostega pennata, Barbilophozia attenuata, Bazzania tricrenata, B. trilobata, Calypogeia neesiana var. meylanii* (sandstone rocks and shaded sandy banks), Lepidozia sylvatica*, L. trichoclados* and Odontoschisma denudatum* (all from old red sandstone rocks), Nowellia curvifolia and Ptilidium pulcherrimum* (willow trunk by a stream). On a crumbling sandstone bank near Alton Pohlia lutescens* and P. pulchella* were found growing together.
[* New vice-county record]
The Society is very grateful to Dr K. M. Goodway, Department of Biology, University of Keele, for his expert local organization, to which much of the success of the meeting was due, and to Mr Perry for leading the field excursion.
G. C. S. Clarke