Position Of Hilum Research Articles

Permineralized Fruits and Seeds from the Princeton Chert (Middle Eocene) of British Columbia: Nymphaeaceae

Nymphaeaceous seeds and their probable fruit remains are described from the Middle Eocene Allenby Formation of Princeton. British Columbia. These seeds are subspheroidal to ovoid, anatropous, exarillate, and operculate. Two openings in the operculum represent the position of hilum and micropyle. Cells of the operculum are radially elongate with straight walls and can be distinguished from cells of the palisade-like outer integumentary layer that have sinuous radial walls. Surface views of cells of the outer integument show sinuous walls with four to 10 undulations per cell. The inner zone of the outer integument is composed of one to two rows of tangentially elongated thin-walled parenchymatous cells. The inner integument is composed of one to two rows of tangentially elongated, thin-walled cells. Two seeds have been found with preserved perisperm. A single vascular strand runs from hilum to chalaza, and a raphal ridge is present. Comparisons to seeds of both extant and fossil Nymphaeales show that these seeds should be included in the family Nymphaeaceae. Allenbya collinsonae Cevallos-Ferriz et Stockey gen. et sp. nov. shows closest similarities to the fossil genera Dusembaya and Palaeonymphaea and may be related to the extant genus Victoria. The description of this new taxon adds to our knowledge of the four lines of nymphaeaceous seed morphology and their evolution. Evolutionary trends within the Nymphaeales include: the establishment of tubercles or small protuberances in the outer integument in one line, and the change in position of the hilum from the operculum to the seed body and development of a broad integumentary zone beneath the palisade in a second line. These fossils show that the family Nymphaeaceae was more diverse in the past and add to our knowledge of the aquatic elements in the Princeton flora.

Fracture Resistance of Soybeans to Compressive Loading

ABSTRACT THE fracture resistance of whole soybeans was measured in terms of average compressive force, deformation, and toughness at seedcoat rupture. Amsoy-71, Corsoy, and Williams varieties at moisture contents of 8, 11, 14, and 17 percent w.b. were quasi-statically loaded in a horizontal hilum and vertical hilum position. Force required to initiate seedcoat rupture decreased as soybean moisture content in-creased from 8 to 17 percent. Soybeans loaded in the vertical hilum position consistently developed seedcoat cracks at lower levels of force than those in the horizontal hilum position. Maximum toughness occurred in the 11 to 14 percent moisture range, indicating an optimum moisture range for absorbing compressive energy. Soybeans loaded in the vertical hilum position required less energy for seedcoat rupture than those in the horizontal hilum position. Maximum allowable com-pressive energy levels often fell below the impact energy levels that would occur during normal dropping and other handling operations.