No abstract

Stems producing regular whorls of branches at the nodes; sheaths the same color as the stem, or proximal ones wholly light brown (but not dark-girdled), b. Tubercles along the ridges of branches appearing (in profile) like sawteeth, the teeth pointed toward branch apex; stomata in a single line on each side of the groove; stem sheaths all colored the same as the stem E. myriochaetum.b. Tubercles of branch ridges appearing square or flattened, in profile; stomata in (2-) 3-4 lines along the flanks of grooves; stem sheaths (proximal ones) often light brown E. giganteum.

Copeland (1947) concurred with Maxon on the naturalness of the group, and restored Cnemidaria to generic rank. This concept was supported by Holttum & Sen (1961), who reinforced the distinctiveness of the genus by pointing out the peculiar character of the spores. They further suggested that some of the free-veined species earlier placed in the genus lacked this type of spore and thus should be excluded. Tryon (1970) included Cnemidaria in his classification of the family, refined the generic concept, and pointed out still another pertinent character to further delimit the genus within the Cyatheaceae: that trichomes are rare or lacking on the adaxial side of the costa. Other genera are characterized by the common occurrence of trichomes along most of the axes, particularly on the adaxial side.Throughout the years, poor or incomplete collecting has contributed to lack of understanding of the generic features of tree ferns. Due to the size of individual plants, collectors either ignore them in the field or are satisfied with a pinna or two. The problem remains a current one. However, enough material (nearly 2,000 specimens) has been gathered for this study to indicate that the group of species as treated here forms perhaps the most natural and distinctive genus in the family. In addition to the characters already noted in this "Introduction," Cnemidaria also has whitish or bicolorous petiole scales, rudimentary paraphyses, arachnoid scurf on the axes, hemitelioid indusia, and pinnae never articulated at the base. These characters, however, may also occur in species of other genera. MATERIALSThis revision is based on the study of nearly 2,000 specimens which were either loaned to me by various institutions or made available to me on visits to their herbaria. I also made several visits to Gray Herbarium to examine specimens on loan to Dr.

Plants terrestrial; rhizome thick-cylindrical to swollen, but never globose, bearing one to two leaves; mature plant 2-11.5 cm. tall; common stalk 0.5-2.5 cm. long; fertile segment 1.5-9 cm. long, with spike 0.3-1.5 cm. long and 1-2 mm. thick; sterile lamina 0.5-2.5 cm. long and 0.2-0.8 cm. wide, elliptic to ovate, acute to rarely obtuse, cuneate to short-attenuate at base, with midvein lacking or very poorly defined; venation somewhat obscured due to the thickened texture, diffuse, reticulate, the areoles mostly with free, included veinlets.Clausen pointed out in his monograph that, on the basis of a few intermediate plants collected in Africa, the separation of O. nudicaule var. tenerum from the typical variety might not be justifiable. In either case, the plants in Guatemala are separable from those of var. vulcanicum, as is designated in the key.Ophioglossum nudicaule L. f. var. vulcanicum Clausen, Mem.

Plants terrestrial, epiphytic, or epipetric (or aquatic in Ceratopteris), greatly diverse in size and shape; rhizome long-or short-creeping to ascending or erect, provided with scales or trichomes, or occasionally glabrous; leaves widely spaced to fasciculate, monomorphous or dimorphous, simple and entire to 4-pinnate or more, circinate in vernation; veins free to areolate, the areoles with or without free, included veinlets; sporangia grouped in definite son or coenosori, or loosely clustered in lines or bands, or without definite pattern; individual sporangia thin-walled (1 cell thick), long-stalked (or rarely the stalk short to vestigial), with a vertical annulus which encircles the capsule but is interrupted by the stalk (or annulus vestigial or nearly so in Ceratopteris); indusium present or lacking, often formed by the modified segment margin; spores monolete and bilateral to trilete and tetrahedral or subglobose, white to brown or blackish, or, in a few genera, ripe ones green (containing chlorophyll).The family is a huge and unwieldy one, with its genera so diverse as to nearly defy circumscription. It contains perhaps two-thirds of the ferns now living, the total being estimated by various authors at 150-180 genera and 6,000-10,000 species. Great, often heated, controversy has raged since the dawn of Taxonomy, as to whether the species ACROSTICHUM LinnaeusTerrestrial plants of low, wet places, most commonly in mangrove swamps; rhizome stout, erect, woody, amply scaly at apex, amply provided with thick (to 7 mm.), spongy roots; leaves quite large, coarse, caespitose, petiolate, monomorphous or essentially so (fertile leaves occasionally somewhat longer and their pinnae slightly more constricted); petiole riot articulate, stout and smooth, glabrous, terete to subquadrangular, adaxially sulcate; lamina pinnate, glabrous or minutely pubescent, firm-herbaceous to subcoriaceous, terminating in a conform (though sometimes reduced), stalked, apical segment, not or scarcely reduced at base, or occasionally with the basal 1-2 pairs of pinnae greatly reduced or merely persisting as spines; rachis smooth, glabrous, terete abaxially, flattened to sulcate adaxially; pinnae stalked, simple, spreading to strongly ascending; venation copiously areolate, the veins distinct and prominulous on both surfaces, the areoles subrectangular to hexagonal, lacking free, included veinlets; sporangia longstalked, completely covering the abaxial surface, intermixed with abundant paraphyses; indusia lacking; spores trilete, tetrahedral, with perine.The genus should be confused with no other in Guatemala. It is distinguished by the simply pinnate leaves, with the abaxial surfaces of the fertile pinnae completely covered by masses of sporangia. It is a tropical or subtropical fern of wet places, most commonly found in mangrove swamps, but sometimes found in the mud of lake shores or river banks. Two species occur in the neotropics, and perhaps two more in the Old World. a. Pinnae widely spaced; fertile lamina with only the distal pinnae ...

No abstract

Five semi‐flexible thermotropic liquid crystalline (LC) polyesters and poly(ester‐amide)s were synthesized and used as matrix resins for Twaron™ aramid‐based ballistic fabrics. The ballistic performance was investigated as a function of the neat resin content. For the most successful liquid crystalline polyester system, the effect of blending with styrene‐ethylene‐butylene‐styrene (SEBS) and polyvinyl butyrate (PVB) rubber was also explored. The best neat resin V50 values were obtained for 20 wt% LC polyester (LCPE)‐Twaron™ composites, that is, 418 m.s−1, whereas SEBS/LCPE and PVB/LCPE modifications resulted in maximum V50 values of 460 and 466 m.s−1, respectively. It was found that the ballistic impact resistance is strongly influenced by the elastic modulus of the resin component and to a lesser extent to the level of adhesion between the resin and fabric. The effect of resin content, resin strength, elongation‐at‐break, and resin toughness on the ballistic impact resistance was found to be small. The best ballistic protection could be obtained when the Young's modulus of the LC resin was in the range of 0.01–1 GPa. This result seems to be in agreement with existing inter‐yarn friction models. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Most American pteridologists are familiar with the rare "Curly Grass Fern," Schizaea pusilla Pursh, and are aware that it occurs only in scattered localities in northeastern North America. Thus far it has been found (with luck) in southern New Jersey and Long Island,