Lower Epidermal Cells Research Articles

Morphometric and Anatomical-Histometric Characteristics of two Varieties of the Species Solanum lycopersicum L. Infected by Cucumber Mosaic Virus

Viruses induce different external and internal symptoms on plants. Our investigations showed that the occurrence and the appearance of symptoms is a result of interaction of a specific virus and its host plant within concrete conditions of the environment. There are many literature data on the impact of viruses on the cell and its organelles and changes in tissue and organs, their structure and function, but very little data on the quantification of most of these changes. Therefore, in this study we determined some morphometric parameters (internode length, stem height, leaf area and weight) and some anatomical-histometric parameters (leaf thickness, upper and lower epidermis thickness, palisade tissue thickness, spongy tissue thickness, mesophyll thickness, area of upper and lower epidermis cells, area of palisade and spongy parenchyma cells, main nerve height and width and ​​vascular bundle height, width and area of the main nerve) of two varieties of tomato plants (var. Saint Pierre and var. Novosadski jabucar) infected by 746-07 isolate of cucumber mosaic virus (746-07-CMV). The results show that the virus exerted influence on all investigated parameters, with some differences depending on the combination of virus/tomato variety. As a consequence of reduction of internodes length and stem height for both varieties, stagnation in growth occurred in higher percentage for the variety of Novosadski jabucar. Area and thickness of leaves were abortive in growth; they had thinner palisade tissue and its cell surface. From this, one may conclude that the productive ability of plants was reduced.

Leaf and stem anatomy of honeybush tea (Cyclopia species, Fabaceae)

The leaf and stem microstructure of commercialised Cyclopia species (Cyclopia intermedia, Cyclopia subternata, Cyclopia maculata, Cyclopia genistoides) is described and illustrated for the first time. Leaflet characters of diagnostic value include the shape, margin (flat or revolute), bundle sheath extensions, crystals (aggregates, solitary crystals and crystal sand), relative size of the upper and lower epidermal cells and thickness of the cuticle. The study revealed an abundance of phenolic compounds, not only in the leaf epidermal cells and leaf bundle sheaths, but also in the secondary phloem, xylem rays, xylem parenchyma and pith, showing that the inclusion of older stems may be acceptable and does not necessarily lower the quality of the product.

Ginkgo Huolinhensis sp. nov. from the Lower Cretaceous of Huolinhe Coal Field, Inner Mongolia, China

Abstract:A new species, Ginkgo huolinhensis sp. nov., with well‐preserved cuticle from the Lower Cretaceous, Huolinhe Formation of Huolinhe Coal Field in Inner Mongolia, China, was studied morphologically and anatomically. The main characters of the new species are found in the leaves which are deeply dissected with narrow lobes, trichomes developed on both upper and lower epidermal cells, a media papilla developed on the periclinal walls for each cell in upper cuticle, and no trichomes on the cuticle of the petioles. These characters of G. huolinhensis sp. nov. distinguish from the known species of Ginkgo previously reported. This study of the new species is beneficial for the taxonomic research of fossil Ginkgo, and should be helpful for a better understanding the paleoenvironment of Ginkgo living in northeastern China during the Early Cretaceous.

Physiological role of anthocyanin accumulation in common hazel juvenile leaves

Common hazel (Corylus avellana L., Fusca rubra Dipp.) juvenile leaves from the periphery of the canopy and thus subjected to high fluxes of solar radiation are characterized by red coloration due to anthocyanin accumulation disappearing in mature leaves. To elucidate the physiological role of anthocyanin accumulation, the interrelations between anthocyanin content, a degree of attenuation by the pigments of the light reaching the photosynthetic apparatus (PSA), and PSA tolerance to photoinhibition in C. avellana juvenile leaves were studied. Absorption spectra were calculated taking into account the light losses due to reflection by the leaf. The analysis of the spectra showed that, in red common hazel leaves accumulating high amounts of anthocyanins in the vacuoles of the upper and lower epidermal cells, up to 95% of visible radiation entering the leaf blade was absorbed by these pigments. The rate of the linear electron transport (ETR) in the chloroplast electron transport chain (ETC) was closely correlated with the anthocyanin content (r2 = 0.87). In red leaves, the saturation of ETR dependence on irradiance was observed at the higher values of PAR than in green leaves. In red juvenile leaves, this value was close to that in mature green leaves tolerant to high light. There were no differences between red and green leaves in the level of non-photochemical quenching, the content of violaxanthin cycle pigments, a degree of their de-epoxidation under natural illumination and at irradiation with high PAR fluxes. Basing on the data obtained, one may conclude that anthocyanins in C. avellana juvenile leaves serve PSA photoprotection, preventing injury of immature PSA with excessive fluxes of PAR.

ANATOMICAL CHARACTERISTICS OF LEAF MESOPHYLL ON ROSA RUGOSA AND THEIR HYBRID PLANT

The variation in structure of the leaf mesophyll tissue on Rosa rugosa and their hybrid plants were anatomically compared. In R. rugosa, the epidermal cells composed large, thick cuticle with wax layers on the abaxial and adaxial side. The lower epidermal cells are significantly developed with enlarged, tightly packed. These cells can be brought about by various stresses, such as drought, waterlogging, salt damage, excess heat, damage to the leaf by pest and other agents. Especially they may also act as a water storage tissue in plants. The palisade cells found tightly packed, and connected to the bundle sheath cells at the level of the phloem. In contrast to the R. rugosa, the thin leaves have long palisade cells that occupy approximately one-third to one-half of the blade thickness in hybrid plants. In these leaves, palisade cells and spongy mesophyll are not clearly differentiated. These cells are loosely arranged and contained intercellular spaces. Epidermal cells on both side flattened and composed thin layers compared to the R. rugosa. In the leaves of R. rugosa, volatile organic compounds (VOCs) such as Rugosal A or pectic substances are observed throughout in the epidermal cells. They stained in red-purplish color with toluidine blue-O. We conclude that the wild rose plant, R. rugosa may be a useful germplasm source for the plant breeders.

Struktur Anatomi Epidermis Daun Lima Kultivar Melon (Cucumis melo L.) Berdasarkan Resistensinya terhadap Jamur Tepung (Sphaerotheca fuliginea Poll)

Powdery mildews are plant diseases caused by fungi, including Sphaerotheca fuliginea Poll. They cause a decrease on leaves health. Plant resistance to Sphaerotheca fuliginea Poll. might have a relationship to leaf anatomical structure, especially to epidermis. Therefore, the aim of this research was to characterize epidermal leaf structure of resistant and susceptible cultivars. This study used two resistant cultivars (PI 371795 and PMAR), one susceptible cultivar (Action 434) and two other cultivars (Fresh 848 and Sakata 144) which are not known their characteristic to powdery mildews. The fifth leaves (counted from the cotyledon) were collected from melon plants which reached early generative development. Leaf epidermal slides were prepared semi permanently. The results showed that the morphological leaves of resistant cultivars have dendatus leaf edges, while the susceptible one has repandus leaf edges. Anatomically, the leaves of PI 371795 had upper epidermal cells with wavy edges, but not in the others. Both PI 371795 and PMAR 5 had irregular shape of lower epidermal cells with curved edges, while leaf epidermal cells from susceptible cultivar tended to have irregular polygonal upper and lower epidermal cells with straight edges and shorter non-glandular trichomes. PMAR 5 had long glandular trichomes. There was significant difference between cultivars in the average of stomata number, the average of stomata index and trichome number on the lower epidermal tissue, but not on the lower epidermal tissue. In the lower epidermis, PI 371 and PMAR 5 had lower average of stomata number and stomata index compared to Action 434. PMAR 5 had higher number of trichomes than susceptible cultivar (Action 434). Meanwhile, Fresh 848 cultivar tends to have similar characters to resistant ones in terms of leaf edges, lower epidermal shape, stomata number and index. Sakata 144 had similar characters to those the susceptible one in terms on leaf edges, lower epidermal cells shape, stomata number and index, but not in trichome number. It may be assumed that the first protection of melon against S. fuliginea Poll. is located on lower epidermal tissue.

不同倍性盾叶薯蓣（Dioscorea zingiberensis）叶表皮形态的比较

通过对二倍体（2x=20）、三倍体（3x=30）、四倍体（4x=40）盾叶薯蓣植株叶片上下表皮细胞密度、细胞形状系数,气孔器大小、气孔指数、气孔密度,以及气孔器保卫细胞叶绿体数与倍性相关性的比较,探讨多倍体在盾叶薯蓣倍性育种上的前景。结果表明：随着倍性增加,盾叶薯蓣表皮细胞密度、气孔器面积、长、宽、以及保卫细胞宽、保卫细胞叶绿体数均明显增大。气孔器面积和保卫细胞宽与倍性成正比,且差异显著,可以作为倍性鉴定的手段之一。

Morphological and anatomical characteristics and taxonomical significance of achene micromorphology ofAchillea phrygiaandA. gypsicola(Asteraceae), endemic to Turkey

Micromorphological and anatomical characters of two Achillea L. species, A. phrygia Boiss. & Bal. and A. gypsicola Hub-Mor., which are endemic to Turkey, were investigated. It was observed that stem length, corymb width, number of capitula and median phyllary shape were diagnostic characters. In the anatomical studies, cross sections were taken from roots, stem and leaves. It was observed that roots of the investigated taxa had a secondary thickening. Endodermis and collenchyma layers were prominent in the stem of both taxa and they had a bifacial mesophyll while the layers of the mesophyll varied. Stomata were anomocytic in both species. We found that there was a significant difference in terms of width of epidermis cells and length of cortex cells in the root, epidermis width and length, collenchyma and parenchyma cells, endodermis length, diameter of trachea of stem, length of upper epidermis cells, width of lower epidermis cells, length of palisade parenchyma and spongy parenchyma cells, diameter of trachea and stomata length of leaf between the two taxa (p<0.05). Scanning electron microscopy (SEM) was used to describe the micromorphology of trichomes and achenes. In A. phrygia, long and eglandular trichomes were more dense on the stem and leaf epidermis. Achene micromorphological characteristics such as size, shape and achene coat were considered to be useful in separating the investigated species.

Establishment of the distinct species status of Polygonum ciliinerve based on morphological and anatomical data

Different opinions regarding the systematic position of Polygonum ciliinerve (Nakai) Ohwi persist in Flora Reipublicae Popularis Sinicae and some provincial floras. The vegetative and reproductive organs of P. ciliinerve were observed using scanning electron microscopy, paraffin sectioning and leaf epidermis isolating methods. The results showed that the main medicinal part of P. ciliinerve was a stem tuber, which originated from an axillary bud on the creeping stem, rather than a root tuber as previously suggested. The leaf upper epidermal cells were nearly oblong in shape; the lower epidermal cells were superficially wavy. Numerous papillae were present on both sides of the leaf veins, and a few of glandular hairs were dispersed on the leaf epidermis of both sides. The transverse sections of main leaf veins and petioles showed 5 and 10 vascular bundles respectively. The pericarp micromorphology showed fovea surface ornamentation. The transverse section of the seed was nearly triangular in shape. These characteristics of P. ciliinerve were obviously different from those of P. multiflorum Thunb. As a result, we suggested that P. ciliinerve should be treated as a species rather than a variant of P. multiflorum.

Significance of the leaf epidermis fingerprint for taxonomy of Genus Rhododendron

Leaf epidermal fingerprints of six species of Rhododendron(Rh. Aureaum, Rh. dauricum, Rh. micranthum, Rh. Mucronulatum, Rh. Redowskianum, Rh. schlippenbachii)were observed by optical microscope with nail polish expression method in Key Laboratory of Forest Plant Ecology of Ministry Education China in Northeast Forestry University in 2004. The leaf morphological features including of stomata types, characters of guard cells, subsidiary cells in lower epidermis were observed. And ordinary cells (in shape and anticlinal walls feature) as well as the trichomes in both sides of the leaves are described in detail. The results showed that there were three types of stoma in six investigated Rhododendron species, from which Pericytic stomata type exists in three species (Rh. dauricum, Rh. micranthum, and Rh. mucronulatum), Anomocytic stomatal type in Rh. Redowskianum, Diacytic stomata type in Rh. aureaum and Rh. schlippenbachii. The sub- sidiary cells of the Pericytic and Diacytic stomata type are different in shape and surface feature between the species, respectively. The or- dinary epidermal cells show a variety from quadrangular to hexagonal, polygonal or irregular in surface view, the anticlinal walls are straight or sinuose. Trichomes (gland scales) are present in the both of the leaf sides in three species (Rh. dauricum, Rh. micranthum, and Rh. mucronulatum). All of these detail leaf features show specific specificity of leave finger print for 6 rhododendrons.

Leaf morphology of 29 Chinese and one Thailand species of the Selaginellaceae and its taxonomic significance

Leaf morphology of 29 Chinese species and one Thailand species of the Selaginellaceae was observed under light microscope and stereoscope. Species examined are rather consistent in leaf morphology. (1) Leaves are usually dimorphic, monomorphic only in few species, not petiolate, with the lateral leaves of the dimorphic leaf species larger than the median leaves, spreading outward or ascending, and the median leaves more or less adpressed on the adaxial side of stem, decussate or imbricate, and arranged in four ranks, while the leaves in the monomorphic leaf species spirally arranged. (2) The cells of the upper epidermis of the lateral and the median leaves are similar to each other, sub-isodiametric, tetragonal or oblong, and the anticlinal walls are straight, arched, sinuate or sinuolate; the cells of the lower epidermis of the lateral and the median leaves are also similar to each other, oblong or elongate, and the anticlinal walls are sinuolate. (3) The stomatal apparatuses, which are of anomocytic or actinoid types, are mainly distributed on the midvein region of upper epidermis of the median leaves and lower epidermis of the lateral leaves. The characters of the leaf macromorphology and of the micromorphology of the epidermal cells as well as the distribution patterns of stomata prove to be important for species delimitations in the Selaginellaceae. The studied species can be differentiated according to the following characters: (1) the shape of leaves (dimorphic vs. monomorphic); (2) the leaf arrangement (spiral vs. alternate); (3) the shape of the anticlinal walls (straight, arched, sinuate or sinuolate); (4) the shape of the cells of upper and lower epidermis (homomorphic vs. heteromorphic); (5) the type of the stomatal apparatus (anomocytic vs. actinoid); and (6) the difference in distribution of stomata on the upper and lower epidermis of the lateral and the median leaves.

Changes in the expression pattern of the plasma membrane H+-ATPase in developing Ricinus communis cotyledons undergoing the sink/source transition.

The plasma membrane (PM) H+-ATPase is thought to play a key role in generating the proton motive force used to drive the uptake and accumulation of solutes in plant cells. Changes in its expression pattern were studied in the Ricinus communis L. cotyledon as it changed from a sink to a source organ. Expression was monitored in 3-, 10- and 14-day-old cotyledons using an antibody to the maize PM H+-ATPase. The antibody labelled a 100-kDa protein in membrane fractions prepared from cotyledons and this protein occurred at higher levels in the PM-enriched fractions compared to those enriched in intracellular membranes. Immunostaining of tissue sections of 3-day-old Ricinus cotyledons (sinks) with this antibody demonstrated that the PM H+-ATPase was highly expressed in the lower epidermal cells and also in the vascular bundles, particularly the phloem. The high expression in the epidermis suggests that these cells may be important in the initial active uptake of solutes from the endosperm. A similar distribution was observed in the 10-day-old seedlings but, in addition, larger, more spherical cells (idioblasts) had developed in the lower and upper epidermal layers and these were also labelled. In 14-day-old seedlings the cotyledons are no longer reliant on nutrients from the endosperm (which has totally degraded) and they are functioning as source organs. This is reflected in a decrease in PM H+-ATPase expression in the lower epidermal cells, apart from idioblasts and stomatal guard cells. The latter were also observed in the upper epidermis. Expression remained high in the vascular bundles of 14-day-old seedlings with strong staining in the phloem.

Characterization of anatomical features and silica distribution in rice husk using microscopic and micro-analytical techniques

Rice husk is a by-product of rice milling process, and a great resource as a raw biomass material for manufacturing value-added composite products. One of the potential applications is to use rice husk as filler for manufacturing lignocellulosic fiber–thermoplastic composites. This study was conducted to examine the silica distribution in rice husk in preparation to use it as reinforcing filler for thermoplastic polymers. Microscopic techniques, such as light microscopy, scanning electron microscopy and field-emission SEM (FE-SEM) were used to observe the surface and internal structure of rice husk. Microscopic examination showed that two main components of husk, lemma and palea consisted of outer epidermis, layers of fibers, vascular bundles, parenchyma cells, and inner epidermis, in sequence from the outer to the inner surface. Histochemical staining showed that epidermal and fiber cell walls were lignified, and the walls of parenchyma and lower epidermal cells were not lignified. The outer epidermal walls were extremely thick, highly convoluted and lignified. The outer surface of both lemma and palea were conspicuously ridged. The energy dispersive X-ray micro-analysis attached to the FE-SEM provided information on the distribution of silica in the husk. Most of the silica was present in the outer epidermal cells, being particularly concentrated in the dome-shaped protrusions. These observations provided valuable background information on the organization of husk tissues and the distribution of silica, which will help optimize processes related to the use of rice husk for making lignocellulosic fiber–thermoplastic composites in our future work.

Arsenic distribution and speciation in the fronds of the hyperaccumulator Pteris vittata.

• Pteris vittata is the first plant reported to be a hyperaccumulator of arsenic (As), and little is known about the mechanisms of As hyperaccumulation in this plant. • Arsenic distribution at the whole plant (fronds) and cellular level was investigated using chemical analyses and energy dispersive X-ray microanalyses (EDXA). Speciation of As in the fronds was determined using X-ray absorption near edge spectroscopy (XANES) analyses. • The majority of As was found in the pinnae (96% of total As). The concentration of As in pinnae decreased from the base to the apex of the fronds. Arsenic concentrations in spores and midribs were much lower than in the pinnae. EDXA analyses revealed that As was compartmentalized mainly in the upper and lower epidermal cells, probably in the vacuoles. The distribution pattern of potassium was similar to As, whereas other elements (Ca, Cl, K, Mg, P and S) were distributed differently. • XANES analyses showed that approximately 75% of the As in fronds was present in the As(III) oxidation state and the remaining as As(V).

Nuclear (DNA, RNA, histone and non-histone protein) and nucleolar changes during growth and senescence of may apple leaves

Quantitative interference microscopy was used to determine changes in nuclear and nucleolar indices (dry mass and cross-sectional area) in upper and lower epidermal cells and adjacent leaf-margin hair cells of the May apple ( Podophyllum peltatum L.) leaves over a 42-day period (after leaves emerged above the ground litter). These indices decreased in a highly correlated manner. A ploidy variation may exist between epidermal cells and leaf-margin hair cells. Using the leaf-margin hair cells model, six nuclear macromolecule indices (total nucleic acid, DNA, RNA, total nuclear protein, histone and non-histone protein), nuclear volume, nucleolar volume and perinucleolar volume (measured using quantitative epifluorescence-phase contrast microscopy) all declined with age (42-day study) in a highly correlated manner. The degeneration of the nucleus and nucleolus in the three leaf locations studied followed the patterns observed for programmed cellular senescence and death (necrosis) in epidermal cells of onion leaf bases (stored tissue; leaf bases did not contain chlorophyll) and human epithelial cells (buccal; cervical). We conclude that the epidermal cells and leaf-margin hair cells from green leaves of the May Apple are ideal for the study of programmed cell senescence and death in plants, especially for the partitioning of this process into the study of: the point-of-no-return (solubilization of the karyoskeleton and loss of non-histone proteins and RNA associated with the karyoskeleton from the nucleus); nuclear pycnosis (loss of nuclear dry mass and volume and loss of nuclear internal support structure); chromatin condensation, margination along the inner nuclear envelope; and DNA-histone degeneration; degeneration of the nucleolus and loss of the perinucleolar zone of exclusion. The characterization of chlorenchyma cells during the 42-day period should now be undertaken (leaf senescence as indicated by the beginning of yellowing about 35 days after emergence) to determine whether these cells with functional chloroplasts undergo nuclear changes like those lacking functional chloroplasts.

Monoclonal antibody MAT-1 against human tyrosinase can detect melanogenic cells on formalin-fixed paraffin-embedded sections.

Immunohistochemical localization of tyrosinase was examined with a monoclonal antibody (MoAb MAT-1) against human tyrosinase on routine formalin-fixed paraffin-embedded sections of 3 normal skin specimens, 15 melanocytic tumors (6 pigmented nevi, 3 juvenile melanomas and 6 malignant melanomas) and 3 non-melanocytic tumors. In the melanotic melanomas, almost all tumor cells were clearly stained with the antibody. In the nevocytic nevi, the nevus cells in lower epidermis and upper dermis were positive for MoAb MAT-1, but negative in middle and lower dermis. All three juvenile melanomas, one amelanotic melanoma, and three non-melanocytic tumors were entirely negative for MoAb MAT-1. Thus, MoAb MAT-1 could recognize the cells with melanogenic activity on routine formalin-fixed paraffin-embedded sections. However, the staining quality was not adequate for normal epidermal melanocytes, indicating that small technical innovations in the immunostaining process such as formalin fixation after PBS washing are required. Nevertheless, MoAb MAT-1 can be expected to be very useful for identifying melanogenic cells on paraffin-embedded sections, because we have to date no other antibody available for it.

Morphological Analysis of Damage to Tomato Leaflets by Tomato Russet Mite (Acari: Eriophyidae)

Morphological damage to tomato leaflets by tomato russet mite (TRM), Aculops lycopersici (Massee), was examined by tissue sectioning. Upper and lower epidermal cells were destroyed by mite feeding. A thickened layer of callous tissue formed adjacent to the parenchyma in regions of epidermal cell death. Underlying parenchyma cells were not damaged, probably due to the short stylet length of TRM. Epidermal cell damage was most prominent near the leaflet mid vein, extending laterally toward the margin. Studies suggested that as mite density on a tomato leaflet increased, the feeding activity of each individual mite was accelerated.

Changes of membrane fluidity and Na+,K+-ATPase activity during cellular differentiation in the guinea pig epidermis.

The dynamic properties of plasma membrane in epidermal cells were determined by means of electron spin resonance using two kinds of doxyl stearic acid spin labeling agents: 5-DSA and 12-DSA. 5-DSA and 12-DSA are stearic acid analogues with a nitroxide radical ring at the 5th and 12th carbon positions, and these motions reflect molecular motion of lipid bilayer surrounding the hydrophilic region and the hydrophobic region, respectively. Guinea pig epidermal cells were separated into three regions of keratinocytes by Percoll density gradient centrifugation; the upper, middle, and lower epidermal cells. The order parameter S values for 5-DSA and 12-DSA incorporated into the isolated keratinocytes increased, suggesting a decrease in the plasma membrane fluidity, as cells approached the upper epidermal cell layer. The Na+,K+-ATPase activity as a plasma membrane-bound enzyme was determined in each epidermal cell region, and was found to decrease gradually as the cells approached the upper layer. Accordingly, the differentiation of epidermal cells in the keratinization process was found to be associated with a decrease in plasma membrane fluidity and with a decline of Na+,K+-ATPase activity.

Freeze-dried surface replicas of tobacco pectin gels and noncutinized lower epidermal cell surfaces compared

Pectic polysaccharides play an important role in the extracellular matrix of land plant tissues. Pectins are found in primary cell walls and in the connecting region between cells, the middle lamella. These polysaccharides are thought to function as a binding material within cell walls and between cells. Pectins contain galacturonosyl residues as a major constituent and varying amounts of neutral sugar residues. A portion of the galacturonosyl residues are methyl-esterlfted. Calcium salts of pectin are thought to be present in primary cell walls and middle lamella. The structure of the calcium bond between interfiber galacturonosyl residues has been suggested by x-ray fiber diffraction work. The pectic acid unit cell indicates that the galacturonosyl residue as viewed down the chain axis is roughly 7.2 x 6.8Å along the two crystallographlc a and b axes. One or two waters of hydration can Increase this size by 3-6Å In freeze-etched preparations or an associated calcium Ion can Increase Its cross-sectional dimensions by about 2Å.

Systematic Inferences from Spore and Stomate Size in the Ferns

Size of equivalent cells has traditionally been assumed to be constant within species and variable between species. Systematists have commonly measured cells with constant form, such as spores and stomates, as a means of distinguishing species and hybrids in polyploid complexes, since the best known factor determining cell size is ploidy level (Stebbins, 1950). Preliminary hypotheses about polyploid evolution can be generated directly from herbarium specimens based on spore and stomate measurement data. The first evidence of a relation between cell size and polyploidy in the ferns was Lawton's 1932 demonstration that prothallial cells, lower epidermal cells, and stomates in induced apogamous races of Dryopteris marginalis and Woodwardia virginica vary directly with ploidy level. Butters and Tryon's 1948 work on Woodsia x abbeae included epidermal cell and annulus cell measurements that corroborated data from spore germination experiments to document an instance of somatic autopolyploidization. More recently a considerable body of evidence has been assembled supporting the contention that spore size is related to ploidy level in the ferns. Manton (1950) noted that Vancouver Island Cystopteris fragilis (n = 84) has smaller spores than Swiss Cystopteris alpina (n = 126). Hagenah (1961) postulated a polyploid series in species of Cystopteris based on spore-size measurements. In a monograph of Cystopteris, Blasdell (1963) concluded that it was possible to infer ploidy level from spore size in that genus. Blasdell assigned ploidy levels to cytologically unknown components of polyploid complexes based only on spore size (see Lovis, 1977 for a critique). Wagner (1966) demonstrated that there were two varieties of Gymnocarpium dryopteris: a larger-spored typical variety, which is tetraploid, and a smaller-spored variety disjunctum, which is diploid. Schneller (1974) recently provided an analysis of ploidy level and spore size in the Dryopteris filix-mas group of Europe. He concluded that ploidy and spore size are positively correlated for diploid to pentaploid cytotypes in a closely knit phylogenetic group. In an exhaustive analysis of spore features of northeastern North American Isoetes, Kott and Britton (1983) provided new insight into spore-size variability. Whereas megaspore variation within sporangia of a single plant, between sporangia of a single plant, and between plants of a population was found to be more or less equivalent and negligible, variation between populations of a species was demonstrated to be twice that between plants of a population. Microspores were found to be slightly less variable. Kott and Britton (1983) suggested that