Abundance, distribution and feeding relations of root/fungal feeding nematodes in a Scots pine forest

In a 15–20 yr old forest of Pinus sylvestris, Tylenchus spp., Paratylemchus spp? and Malenchus tantulus were the most abundant stylet-bearing nematodes. Soil layers and ground cover affected the abundance. Mycophagy was observed for Tylenchus sp., M. tantulus, Aphelenchoides sp. and Tylencholaimus stecki. Feeding on roots of the forest grass, Deschampsia flexuosa was recorded for W. tantulus, Paratylenchus spp? and Rotylenchus sp. The latter fed also on pine roots. Connections occurred between feeding habits and field distribution. The facultative feeding habit of M. tantulus probably allowed this species to reach higher numbers under D. flexuosa. The importance, in the field, of the grass Calamagrostis arundinacea for Paratylenchus spp? was confirmed by laboratory experiments. As pine was a non-host, these nematodes were probably grass feeders. Paratylenchus spp? dominated the obligate root feeders with forest grass being a key-factor for the group abundance. Suspected high densities of Paratylenchus spp? on clearings should not affect the growth of pine seedlings and although Rotylenchus sp. to some extent reduced seedling growth its pathogenic status on P. sylvestris was doubtful.     

Nematodes in Scottish forest nurseries

Seven hundred soil samples from 41 forest nurseries were collected between 1972 and 1975 and examined for plant parasitic and predatory nematodes. Rotylenchus goodeyi, Trichodorus primitivus, Cephalenchus emarginatus and Tylenchus davainei occurred in most nurseries but their numbers were generally lower than those of R. robustus and Paratrichodorus pachydermus. In a glasshouse experiment as few as 10 R. robustus decreased the growth of Sitka spruce seedlings. It was estimated that Rotylenchus and trichodorid nematodes probably retarded the growth of some seedling trees in eight of the nurseries sampled. During the survey, Trichodorus sparsus was found for the first time in Great Britain and Paralongidorus maximus for only the third time. Since both these species were found in nurseries they were probably introduced and are ideally situated to be more widely disseminated.     

Occurrence and correlations of nematodes,Fusarium oxysporum and edaphic factors on banana plantations

Problems caused by nematodes and Fusarium wilt (Panama disease) on banana plantations are responsible for yield losses and are limiting to its cultivation. In the state of Goias, there is little information about the nematode occurence on this crop, and its relation with the incidence of Fusarium oxysporum f.sp. cubense (Foc). This research had the purpose to identify the occurrence of plant‐parasitic nematodes on banana plantations and to verify its correlation with the Fusarium wilt and with the soil attributes (pH, texture, nutrients). Twelve banana orchards in the state of Goias were sampled in the municipalities of Anapolis, Caiaponia, Goiatuba, Itaguaru, Itumbiara (two areas), Jatai, Morrinhos, Ouro Verde, Palestina, Taquaral and Uruana. All sampled areas, except Morrinhos, revealed contamination with Foc, and all areas had different genera of nematodes either in the soil or in the roots samples. Meloidogyne sp., Helicotylenchus sp. and Rotylenchus sp. were the main genera of plant‐parasitic nematodes found in the samples, with Meloidogyne sp. and Rotylenchus sp. being the most dominant and abundant genera. The presence of Pratylenchus sp. increases the population levels of F. oxysporum. Helicotylenchus sp. is highly correlated with high concentrations of Mn. High population density of Meloidogyne sp. was found in irrigated areas with low concentrations of P, Ca, Mg and soil pH.     

Plant parasitic nematodes associated with ornamental plant Pseuderanthemum atropurpureum in Aligarh district of western Uttar Pradesh

A survey was conducted to determine the nematodes associated with the soil, substratum and roots of the ornamental plant, Pseuderanthemum atropurpureum, grown in the Aligarh district of western Uttar Pradesh, India. Ten genera of plant parasitic nematodes, viz. Meloidogyne spp., Helicotylenchus sp., Hemicriconemoides sp., Hoplolaimus sp., Xiphinema sp., Pratylenchus sp., Trichodorus sp., Tylenchorhynchus sp., Aphelenchoides sp. and Rotylenchus sp., were isolated from 345 soil samples collected from 15 different localities. Our study indicates that among the 10 genera of the plant parasitic nematodes, Meloidogyne spp. was widely spread in all the examined localities of Aligarh district, except at Khair. It was observed that the population density and diversity of nematodes in all the soil samples was not uniform. Meloidogyne spp. showed the highest absolute frequency and relative frequency followed by Helicotylenchus sp., Hemicriconemoides sp., Xiphinema sp., Hoplolaimus sp., Pratylenchus sp., Trichodorus sp., Tylenchorhynchus sp., Aphelenchoides sp. and Rotylenchus sp. Since no records are available in the literature related to the association of root-knot nematode in P. atropurpureum, it is worthy to note that this study may be considered as a new hope towards further study of the interaction between the root-knot nematode and ornamental plant P. atropurpureum if any.     

Pararotylenchus n. gen. (Pararotylenchinae n. subfam., Hoplolaimidae) with Six New Species and Two New Combinations

A new subfamily, Pararotylenchinae, (Hoplolaimidae) is described. It includes a single genus, Pararotylenchus n. gen., six new species, attd two new combinations, Pararotylenchus (syn. Tylenchorhynchus) brevicaudatus (Hopper, 1959) n. comb. and Pararotylenchus (syn. Rotylenchus) pint (Mamiya, 1968) n. comb. Pararotylenchinae is similar to certain other Hoplolaimidae, such as Rotylenchinae, with respect to most characters including the short tail, the position of the phasmids near the anus, and the relatively great distance of the dorsal gland orifice from the base of the stylet knobs. The lip region, as observed with the scanning electron microscope, conforms to the basic pattern for Hoplolaimidae. The labial disc is round with slit-like amphidial openings at the lateral sides of the periphery of the disc. The distinctive anterior-most lip annule is segmented into six sectors. Unlike other Hoplolaimidae, however, the esophageal glands of Pararotylenchinae form a basal bulb similar to that of Tylenchorhynchidae; other characters do not resemble Tylencborhynchidae. Specimens of Pararotylenchus have been recovered only from cool regions at high elevations and Pacific coastal areas in the Western United States, Japan, and Korea.     

Comparison of centrifugal and other methods for standardization of extraction of nematodes from soil

The extraction of many genera of nematodes from four different soil types by sedimentation, mobility, sieving and centrifuging was compared. All methods were found to extract similar numbers of nematodes. Centrifuging was the most versatile technique and the best for clay soils. Baerman sieving was generally poor and particularly so for sands and for the genus Tylen-chorhynchus. Rotylenchus was the only genus of those identified that was extracted equally well by all techniques. Centrifugal extraction was selected as the routine method for surveys as it was effective on all soil types, was less likely to be subject to variation and, although poor for Longidorus, extracted a wider spectrum of nematodes.     

Sphagnum divinum (sp. nov.) and S. medium Limpr. and their relationship to S. magellanicum Brid.

Sphagnum magellanicum has been viewed as being a predominantly circumpolar species in the northern hemisphere, but it occurs in the southern hemisphere and was originally described from the southern parts of Chile. It is an ecologically important species in mire ecosystems and has been extensively used as a model to study processes of growth, carbon sequestration and peat decomposition. Molecular and experimental studies have, however, revealed genetic structure within S. magellanicum, and morphological differences associated with these genetic groups. Here we describe Sphagnum divinum in Sphagnum subgenus Sphagnum (Sphagnaceae, Bryophyta) as a new species, based on molecular and morphological evidence. Sphagnum medium is reinstated as a distinct species and is epitypified. Consequently, a new species concept of S. magellanicum is presented including an epitypification. Important morphological characters to separate these three species in the field and under the microscope are presented. Ecology and distribution differ among the species; S. divinium has a wide habitat range including mire margin, forested peatlands and moist heaths, and a circumpolar distribution around the northern hemisphere. Sphagnum medium seems to be more restricted to ombrotrophic mire expanse habitats and shows an amphi-Atlantic distribution in the northern hemisphere. Sphagnum magellanicum has a very broad ecological niche in peatlands and is found in most mire habitats in Tierra del Fuego on the southern tip of South America.     

Chassalia magnificens sp. nov. and C. chrysoclada comb. nov. (Rubiaceae) from central Africa

Chassalia magnificens, a new species from the Albertine Rift in eastern Democratic Republic of Congo, is described and illustrated. The species is recognised inter alia by its large stipules and montane habitat. Chassalia chrysoclada is a new combination for a widespread, but hitherto overlooked, central African species originally described in the genus Psychotria. Chassalia chrysoclada is related to C. pteropetala (K. Schum.) Cheek but lacks the bicostate twigs and dorsally winged corolla lobes of that species.     

PALEOZOIC LYCOPSID FRUCTIFICATIONS. I. LEPIDOCARPON PETRIFACTIONS

A reinvestigation of the 4 American species of Lepidocarpon described from petrifactions and of Illiniocarpon cadyi, also described from petrifactions, shows that they are all conspecific. When they, in turn, are compared with specimens of the British petrifaction L. lomaxi, no significant differences can be demonstrated. The criteria cited as diagnostic for the American petrifaction species of Lepidocarpon were found to fail as bases of discrimination when 400 specimens of Lepidocarpon found in coal balls of Pennsylvanian age were studied. Measurements and observations made of a sample size of 136 of these 400 specimens reveal a degree of variation compatible with that of a single species. All previously described American and British petrifaction taxa fall within (or not significantly beyond) this range of variability of a single species as determined from this sample. Additional evidence concerning the 3-dimensional sporophyll structure of this one species of Lepidocarpon and the configurations obtained by certain planes of section through it have served to demonstrate that Illiniocarpon cadyi is in reality a taxon based on sectioned structures of the sporophyll of this Lepidocarpon species. Under the rules of priority, this species of Lepidocarpon and the following are assigned to Lepidocarpon lomaxi: Illiniocarpon cadyi, Lepidocarpon ioense, L. magnificum (megasporangiate form), L. crenatum and L. palmerensis. On the basis of the morphological evidence, the British petrifaction described as Lepidocarpon wildianum is also equated with L. lomaxi.     

On Chytridium braun,Diplochytridium N. G., and Canteria N. G. (Chytridiales)

Summary The operculate genus Chytridium Braun is emended and restricted to approximately 25 known species and several incompletely known members which lack an apophysis and develop much like species of Rhizophydium, insofar as the zoosporangium and absorbing or rhizoidal system are concerned, and form endobiotic or intramatrical resting spores. This interpretation corresponds fairly closely to Braun's diagnosis of the type species.A new genus, Diplochytridium, is established to segregate the former Chytridium species with an endobiotic or intramatrical apophysis or prosporangium and resting spores, which may develop sexually or asexually. Some of these species have a well-defined endo-exogenous alternation of growth and development in which the apophysis appears to function as a prosporangium. As interpreted here, Diplochytridium includes approximately 20 of the known species.Another new genus, Canteria, is created for a parasite of Mougeotia which Canter first described as a species of Phlyctidium but later found to develop endobiotic resting spores or zygospores by the fusion of conjugation tubes.     

CHROMOSOME NUMBERS IN COMPOSITAE. IV. AMBROSIEAE

New chromosome observations are reported for 30 species and varieties from 4 genera of Ambrosieae: Ambrosia (including Franseria), Diceria, Hymenoclea and Iva. Neither polyploidy nor aneuploidy is known in the genera Dicorea, Hymenoclea or Xanthium. Aneuplcid reduction appears to have played a role in the genome evolution of several species of Iva and Ambrosia. Polyploid species occur in both Iva and Ambrosia and polyploid series exist for at least 5 species or species aggregates of the latter. All available evidence indicates that the primitive chromosome number for the tribe is x = 18, differentiation and speciation having occurred at this level, which is here termed diploid. The group, however, must ultimately have been of polyploid origin from forms with x = 9.     

CELLULAR SLIME MOLDS OF SWITZERLAND. I. DESCRIPTION OF NEW SPECIES

During the study of the distribution of cellular slime molds in Swiss forest soils, three new species were isolated and studied in culture, namely, Dictyostelium fasciculatum, Dictyostelium polycarpum and Polysphondylium filamentosum. The first is cosmopolitan, the latter two are known only from Switzerland. Dictyostelium polycarpum is a very delicate species and is the first species reported which is restricted to a high altitude environment. It is characterized by a coremiform habit, reminiscent of D. polycephalum, and relatively long reniform spores. Dictyostelium fasciculatum is a larger species which resembles D. mucoroides in gross morphology but is much closer to Polysphondylium in its life cycle pattern and behavior. Polysphondylium filamentosum is only the third well-defined species of the genus to be described. It produces filamentose principal and lateral axes. Optimum temperature for all three is around 20 C, somewhat below that of most other species in the family.     

Studies in Heterobasidiomycetes,Part 38*)Sphacelotheca polygoni-persicariae G. Demi & Oberw. spec. nov.

A new species, Sphacelotheca polygoni-persicariae, parasitizing the ovaries of Polygonum persicaria L. is described. This smut, collected several times in Madeira, Portugal, differs from other species of that genus, by its host plant and the reticulated teliospore ornamentation. On the basis of the morphological and ultrastructural characters of S. polygoni-persicariae, in connection with some recently published data on siderophore formation and 5S ribosomal RNA sequences it can be assumed that 1) members of the genus Sphacelotheca are separated from typical Ustilago species of Poaceae, 2) Sphacelotheca is restricted to species parasitizing Polygonaceae, and 3) species of Sphacelotheca and Microhotryum as well as those Ustilago species which parasitize in the flowers of Polygonaceae are closely related.     

Amomum dampuianum and A. mizoramense spp. nov. (Zingiberaceae) from Mizoram,northeast India

Two new species of Amomum (Zingiberaceae) from Mizoram are described and illustrated: A. dampuianum and A. mizoramense. Photographs, a comparison with the allied species A. corynostachyum and A. hypoleucum, and a key to the species of Amomum known in Mizoram is also provided.     

SPORE MORPHOLOGY IN THE CYATHEACEAE. I. THE PERINE AND SPORANGIAL CAPACITY: GENERAL CONSIDERATIONS

The literature on cyatheaceous spore morphology relative to the presence of a perine layer is reviewed, and evidence based on a sodium-hydroxide assay is presented indicating that the outer scultpine layer in certain cyatheaceous spores is perine. Perine so defined characterizes Metaxya, paleotropical and certain neotropical species of Sphaeropteris, nearly all species of Alsophila, all species of Nephelea, and certain species of Trichipteris and Cyathea. It is lacking in Lophosoria, many species of Trichipteris and Cyathea, and all species of Cnemidaria. Two major patterns of spore number per sporangium in the family are reported. Lophosoria, Sphaeropteris, Trichipteris, Cyathea, Cnemidaria, and probably Metaxya are characterized by 64-spored sporangia, whereas most species of Alsophila and all species of Nephelea are characterized by 16-spored sporangia. The congruence of this generic distribution of sporangial-capacity types with Tryon's phyletic arrangement of cyatheaceous genera supports the naturalness of his system. The intrasporangial germination of spores retained in dehisced and dispersed sporangia supports the suggestion that decreased spore number per sporangium in Alsophila and Nephelea may relate to the role of the sporangia as dispersal units. The decreased number of spores per sporangium is associated with a trend toward increase in the number of sporangia per sores, with the highest known count approaching 1000 sporangia per sorus. The Alsophila-Nephelea evolutionary line has probably not been ancestral in the phylogeny of the more advanced groups of ferns.