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For solid specimens, Young's modulus is commonly determined from straightforward uniaxial tension experiments. However, honeycomb specimens are far more challenging to test in tension, and it is therefore desirable to conduct bending experiments to determine Young's modulus. The premise of this work is that the bending response of honeycomb specimens may be significantly different from that of solid specimens, and therefore it is necessary to establish a sound protocol for the determination of the axial Young's modulus of honeycomb specimens under bending. Toward this goal, we present results of a study that combines experimental, finite element simulation, and classical beam theory approaches. These results confirm that accurate measurements of Young's modulus of honeycombs require careful consideration of the specimen geometry and analysis of the data. We demonstrate that the use of conventional Bernoulli-Euler's beam theory to interpret the data requires very slender specimens. We also show that less slender specimens can be used if the experimental data is interpreted on the basis of three-dimensional elasticity theory and numerical simulations. A third option is to use a combination of moderately slender specimens and Timoshenko's beam theory.

It is demonstrated that three-dimensional single- and double-layer Stokesian potentials can be computed using fast solution methods for the N-body electrostatics problem. This allows one to develop fast iterative solution methods for a broad class of boundary integral equations corresponding to three-dimensional Stokesian many-particle problems.

A boundary element method for solving three-dimensional linear elasticity problems that involve a large number of particles embedded in a binder is introduced. The proposed method relies on an iterative solution strategy in which matrix—vector multiplication is performed with the fast multipole method. As a result the method is capable of solving problems with N unknowns using only O(N) memory and O(N) operations. Results are given for problems with hundreds of particles in which N"O(105). ( 1998 John Wiley & Sons, Ltd.

Investigated client self-disclosure and client perception of counselors (as expressed in counselor evaluations) as a function of the sex, attractiveness and status of the counselor, and the sex of the client. Counselor gender and attractiveness were established by means of stimulus photographs; counselor status was defined in terms of education and experience. Ss (160 college students) first rated their counselors on intelligence and empathy; they then completed Jourard's Self-Disclosure Questionnaire while role-playing clients in therapy. A four-factor between-Ss analysis of disclosure scores revealed that clients disclosed more of themselves to male than to female counselors when the counselors were high in either status or attractiveness. Results supported the hypothesis that the effect of counselor gender on client disclosure depends on an interaction of counselor gender with other counselor variables.

The seed coats of Gnetum gnemon L., G. ula Brongn., G. montanum f. parvifolium (Warb.) Mgf. and G. neglectum Bl. consist of three layers. The outer layer or sarcotesta is mostly parenchyma but contains some sclereids and fibers and a series of simple vascular bundles. The middle sclerotesta forms masses of sclereids in varying shapes and numbers, sometimes extending as a basal plate, and is usually thicker near the micropylar tube. The second layer also contains a series of small vascular bundles that reach the apex. Depending on the species, the middle layer is sometimes nearly free from the outer layer, may be partially fused with it, or completely fused to it at maturity. The innermost layer of the seed coat constitutes the endotesta which is membranous and only rarely contains sclerenchyma. It possesses a dichotomous venation system with varying degrees of anastomosing, depending upon the species. The above species show qualitative and quantitative differences in their sclerenchyma and laticifers. Seed coat anatomy may be useful in the diagnosis of some species. The trends of evolution of seed coat structure within these four species of Gnetum are discussed, and a comparison of tissue layers and vasculature with certain fossil pteridosperms is made, especially in the Trigonocarpales.

MATERIALS AND METHODS.-The material, collected in South-West Africa or grown in Berkeley, California, is the same as that used in the seedling study (Rodin, 1953b) and the same techniques have been applied. Approximately 24 seedlings were used in this investigation. Mature leaves and attached woody portions of the stem required considerable softening due to extensive fiber and sclereid development. Gifford's (1949) technique, using 20 ml. glacial acetic acid in 80 ml. 60 per cent ethyl alcohol, proved satisfactory on most imbedded tissues. For the more heavily sclerified tissues, the third schedule of Foster and Gifford (1947), a mixture of 10 ml. glycerine, 10 ml. hydrofluoric acid, and 80 ml. 95 per cent ethyl alcohol, was most helpful.

RODIN, ROBERT J. (Calif. State Polytechnic Coll., San Luis Obispo.) Anatomy of the reproductive bracts in Welwitschia. Amer. Jour. Bot. 50 (7): 641-648. Illus. 19t3.-The anatomy, including venation patterns, of the nodal bracts, sterile cone bracts, and fertile cone bracts of male and female cones is discussed. Two traces which dichotomize are present in each member. Occasional anomalous traces in the perianth have been discovered. Details of sclereids, fibers and gum canals are given. The connate nature of the bracts is described. T'he homologies of these organs are

THE LEAF OF a mature plant of Welwitschia has Lhe same basic pattern, with some modification of cell types, as that of the oldest seedling leaves studied (Rodin, 1958). All leaves have isolateral symmetry, but only leaves of older plants contain numerous sclereids. Hooker (1863) gave the first description of a mature leaf, and other workers have made additional contributions (Pearson, 1929; Sykes, 1910a; Takeda, 1913a). The structure of the leaf will be discussed according to the three primary tissue systems. THE EPIDERMAL SYSTEM.-The epidermal system consists of a single layer of cells on the upper and lower surfaces of the leaf. From the surface epidermal cells appear polygonal with from three to five sides. The lateral walls are thickened, the corners rounded (fig. 8). At the leaf base epidermal cells form neat rows (Takeda 1913a, fig. 4), but cells in more distal parts of the leaf are arranged with less regularity. Three distinct layers are present in the heavily thickened outer wall of epidermal cells as observed by Bleisch (1891), Sykes (1910a), Takeda (1913a), and by this author (fig. 9, 10). First, a thin outer non-granular cutinized layer occurs, in which no laminations can be detected. Apparently it is not a waxy layer external to the cell wall, but consists of particles of cutin laid down within the wall. Secondly, there is a thick, middle granular cutinized layer in which granules have been considered to be calcium oxalate by Solms-Laubach (1871) and Bleisch (1891). The third layer, very thick in mature material, is non-granular, noncutinized, laminated, and innermost. Lignin was not detected by this author in any of the layers and cellulose is probably the chief constituent of epidermal cell walls. The cutin in the two outer layers was detected by the use of Sudan IV, a specific stain for fatty substances. Takeda (1913a) reported on the ontogenetic development of the stomata: the two guard cells and the subsidiary cells originate from a single epidermal cell. In the present research it was observed that only after the guard cells begin to elongate do they assume their characteristic sunken position. Tests with Sudan IV reveal cutin in the outer cell walls of the subsidiary and guard cells, as in other epidermal cells. However, in disagreement with Ta