A key to the growthforms of mosses and liverworts and guide to their educational value

Mosses and liverworts have considerable potential as a resource for use in environmental studies. However, these small plants are seldom studied in the field, mainly because they can be difficult to identify. It is suggested that this identification problem may be circumvented by using a system of classification of growth-form types, similar to the kind used for lichens in atmospheric pollution studies. Each growth-form is related to a characteristic range of environmental conditions. This article outlines the value of bryophyte growth-forms as an educational resource and includes a key to growth-forms, developed and tested with teachers, students, and naturalists. The key is easy to use and one does not need to be familiar with bryophyte taxonomy or theories on the adaptive significance of structural characteristics.     

四川省藓类植物新记录

在对四川省第一高峰贡嘎山的野外调查和1 000余份采集标本鉴定的基础上,现已知贡嘎山有藓类植物40科,133属,321种.其中,隶属于10科,12属的12种为四川省苔藓植物新记录种.该文就新记录种进行详细报道,为中国和四川省的苔藓植物区系研究提供新的资料.     

Morphology of superficial postnatal cerebral cortex with special reference to synapses

Summary The ultrastructure of layers I and II of the motor cerebral cortex of rat brain has been studied at birth, 4, 7 and 14 days postnatal and in the adult.Compared with the adult, neonatal rat motor cortex exhibited a large extracellular space which decreases with increasing age. At all stages studied the neurons were seen to contain the organelles usually found in adult neurons. Growth cones were present in decreasing numbers up to 14 days old.Synapses were detectable at birth and there was an obvious increase in their number throughout the postnatal development. At the earliest stages studied there was a lack of specialization characteristic of the adult. Many synapses were either avesicular or relatively so and lacked the high degree of modification of adult pre- and postsynaptic membranes. By 7 days after birth many synapses existed which in all morphological respects resembled those of the adult, and by 14 days, the majority were of the adult type.These findings, particularly with reference to the postnatal development of synapses, have been discussed in relation to the known electrophysiological findings.The authors wish to express their thanks to Mr. R. Birchenough and Mr. J. Manston for their technical assistance.     

Bryophytes as experimental models for the study of environmental stress tolerance: Tortula ruralis and desiccation-tolerance in mosses

The development of a complete understanding of how plants interact with the environment at the cellular level is a crucial step in advancing our ability to unravel the complexities of plant ecology particularly with regard to the role that many of the less complex plants (i.e., algae, lichens, and bryophytes) play in plant communities and in establishing areas for colonization by their more complex brothers. One of the main barriers to the advancement of this area of plant biology has been the paucity of simple and appropriate experimental models that would enable the researcher to biochemically and genetically dissect the response of less complex plants to environmental stress. A number of bryophytes model systems have been developed and they have been powerful experimental tools for the elucidation of complex biological processes in plants. Recently there has been a resurgent interest in bryophytes as models systems due to the discovery and development of homologous recombination technologies in the moss Physcomitrella patens (Hedw.) Brach & Schimp. In this report we introduce the desiccation-tolerant moss Tortula ruralis (Hedw.) Gaert., Meyer, and Scherb, as a model for stress tolerance mechanisms that offers a great deal of promise for advancing our efforts to understand how plants respond to and survive the severest of stressful environments. T. ruralis, a species native to Northern and Western North America, has been the most intensely studied of all bryophytes with respect to its physiological, biochemical, and cellular responses, to the severest of water stresses, desiccation. It is our hope that the research conducted using this bryophyte will lay the foundationfor not only the ecology of bryophytes and other less complex plants but also for the role of desiccation-tolerance in the evolution of land plants and the determination of mechanisms by which plant cells can withstand environmental insults. We will focus the discussion on the research we and others have conducted in an effort to understand the ability of T. ruralis to withstand the complete loss of free water from the protoplasm of its cells.     

A morphological classification of plants,with special reference to the New Zealand alpine flora

Abstract. A plant is a complex of integrated systems (leaves, leaf groups, stems, roots, inflorescences), coexisting side by side or superimposed on each other to produce the life form (orphysiognomy) of the individual. The classic Raunkiaer classification based fundamentally on one character (apex position) is insufficient for the purpose of a functional classification. Five keys are given to determine the categories of:

• 1) the plant silhouette or general shape resulting from a combination of other systems, with 11 categories proposed;
• 2) the leaf group, with 14 categories;
• 3) the stem, with 27 categories;
• 4) the root, with 5 categories; and
• 5) the inflorescence, with 3 categories.

Each plant can be named according to the category or model of each of the five different systems that they most resemble, or by using only the name(s) of systems which are more conspicuous than others. Characters are selected primarily for their influence on form and secondarily on size. This scheme allows for detailed studies of a flora in terms of morphological characteristics (alone or in systems), expressed as frequency of occurrence of each character in the flora. Characters can be analysed separately (e.g. entire margined leaves), as a combination of characters (e.g. leaf groups) or as a combination of systems (e.g. rosettes without stems). Thus correlations between environmental variables and plants canbe made with more precision than in previous classification schemes. The classification also serves as the framework for including additional morphological data and incorporating new models. The New Zealand alpine flora is used as a test case and to exemplify the classification.     

Scapania paraphyllia,a new synonym of Scapania koponenii (Marchantiophyta,Scapaniaceae) with special reference to paraphyllia,pseudoparaphyllia, and paraphyses

Scapania paraphyllia T.Cao, C.Gao, J.Sun & B.R.Zuo and S. koponenii Potemkin are both endemic to China. They share considerable morphological similarities except that the former species has pseudoparaphyllia. In order to elucidate the taxonomic status of the two species, we investigated morphological characters possessed by their type specimens and additional collections, and reconstructed a species phylogeny for S. koponenii, S. paraphyllia, and closely related species. The phylogenetic trees were constructed using maximum parsimony, maximum likelihood and Bayesian inference analyses based on the nuclear marker nrITS and the plastid markers trnL-F region and atpB-rbcL spacer. Both morphological and molecular evidence contradicted the hypothesis that S. paraphyllia and S. koponenii are separate species. The pseudoparaphyllia reported for S. paraphyllia are confirmed as paraphyses. The paraphyllia, paraphyses, and pseudoparaphyllia in Scapania are discussed.     

Rheumatoid nodules. A lightmicroscopical study with special reference to fibrin and fibronectin

The presence and localization of fibrin and fibronectin in rheumatoid nodules were studied using an indirect immunoperoxidase technique on tissue specimens fixed in formaldehyde, embedded in paraffin and pretreated with pepsin and testicular hyaluronidase. Three zones characteristic for rheumatoid nodules was recognized. Central area with necrosis, containing at least in part fibrinogen-antigenic material and fibronectin especially in the peripheral part of the necrotic area. Around the necrosis a layer of mesenchymal cells in a palisade arrangement was found. Especially in the external part of this layer fibronectin was demonstrated around and between the cells, where fibrin was absent. Peripherally, a zone of non-specific granulation tissue containing moderate amount of fibronectin decreasing towards the surround mature connective tissue, was seen. In the border of the cellular layer vessels were found in variable amount. In some of the vessels vasculitis was demonstrated with the presence of inflammatory cell infiltration, fibrin deposition and occasionally thrombosis. The pathogenesis of the inflammatory reaction in rheumatoid nodules is discussed.     

Early morphogenesis in the platyhelminthes with special reference to egg development and development of cestode larvae

Early development of fertilized eggs is reviewed for the main groups within the phylum Platyhelminthes (Turbellaria, Temnocephaloidea, Monogenea, Digenea, Cestodaria and Cestoda). The Turbellaria show two different patterns of embryological development consequent on whether yolk material is contained within the ovum membrane (endolecithal) or whether yolk is added to the outside of the ovum (ectolecithal). In the parasitic groups, those that are oviparous or ovoviviparous produce shelled eggs of the ectolecithal type and, in addition, there are viviparous forms in which egg development shows variations and the amount of yolk, where present, is reduced. In every case examined, however, cleavage is of the spiral type. Within the Cestoda, clear distinction is made between those groups (orders) of worms which are oviparous as compared to those which are viviparous. It is suggested that oviparity is more primitive (ancestral) than viviparity based on adult morphology and on the evidence of life-cycle studies.The continued, post-oncospheral development of cestodes is described as is the ultrastructure of various representative cercoid larval forms. These include: the procercoid of Pseudophyllidea and Haplobothrioidea; the cercoid of Tetraphyllidea; and, within the Cyclophyllidea, the cercoscolex of the Dilepididae, the cysticercoid of the Hymenolepidae, and the cysticercus of the Taeniidae. During post-oncospheral development, in every case examined the posterior part of the developing larva, the cercomer, can be characterized by a microvillar tegument (at least during early development) whereas the more anterior larval body itself, destined to develop in the definitive host, develops microtriches. Modifications to the cercomer, and its microvilli, in the later stages of post-oncospheral development, occur particularly in the more advanced Cyclophyllidea such as the Taeniidae and in some Hymenolepididae.     

Immunohistochemical study of the postnatal development of pituitary thyrotrophs in the rat,with special reference to cluster formation

Summary The postnatal development of rat pituitary thyrotrophs was investigated immunohistochemically on days 1, 3, 5, 10, 15 and 25. Fetal thyrotrophs are strongly immunoreactive. In the postnatal period, however, weakly immunoreactive thyrotrophs increase in number to constitute clusters on days 3–5. The numbers and dimensions of the clusters reach a maximum on day 10. Thereafter the clusters break down to give rise to single, scattered neogenic thyrotrophs. Thyrotrophs in clusters on day 10 were investigated by electron microscopy in adjacent sections. They can be characterized as an immature type of basophil, according to the classification of Yoshimura et al. (1977): 1) Type I basophils, which are irregularly shaped with elongate processes, and characterized by rows of secretory granules about 100 nm in diameter. 2) Type I/II basophils, i.e., forms intermediate between Types I and II, containing less numerous secretory granules about 100–150 nm in diameter. Type II basophils which correspond to the classical thyrotrophs are not fully developed on day 10. Thus, most thyrotrophs develop from the clusters in the neonatal period. Such neogenic thyrotrophs retain the immature characteristics of Type I and I/II cells and may develop into Type II cells during subsequent maturation.