Critical materials were authenticated by an expert in the tribe and by recent annotation labels. Authenticated fruit and seed samples, selected to exhibit the range of morphological characters within a genus, were used to collect descriptive data that were recorded in a DELTA database and to prepare illustrations. Samples were documented either by voucher herbarium specimens or by specimens deposited in the U.S. National Seed Herbarium (BARC), Beltsville, Maryland, and a list of these specimens was filed in the herbarium. Additional fruit and seed samples, many identified by comparison, were used to augment the survey of each genus.
Fruit and seed topography was observed at 10 to 30 magnifications, using a dissecting stereoscopic microscope equipped with an ocular micrometer. Recorded observations were made at 10 magnifications, except as noted.
In preparing seeds for dissection, mature seeds of representative size and shape were drilled, with a miniature electric drill. The testa was penetrated one or more times, depending on seed size, in areas removed from the embryonic axis. Drilled seeds were placed in a softening solution of 74 percent distilled water, 25 percent methyl alcohol, and 1 percent dioctyl sodium sulfosuccinate (aerosol OT). They were kept in solution for one-half to 24 hours, depending on the consistency of the testa. The testa was easily removed along with the endosperm when present. Embryos were drawn with the aid of a camera lucida fitted on a stereoscopic microscope. Illumination was provided by an above-stage fiber optic system, which split the light into one beam for the microscope and one for the camera lucida. Drawings were prepared first in pencil and then in India ink on Dupont Cronaflex U-C Tracing Film.
The light photographs were made with a Leitz copy camera, mounted on a light stand, using 4-5 Polaroid type 55 film. Mature fruits and seeds usually were photographed in face view at 1 magnification and either enlarged or printed contact size, using standard printing techniques.
For the SEM, seeds were cleaned by hand and attached by adhesive to aluminum specimen stubs and then stored in a desiccator for at least 24 hours before coating. Coating with gold palladium was done in a Technics Hummer V Sputter Coater. Chamber pressure was reduced to 20 millitorrs and then flushed five times with argon before chamber stabilization at 100 millitorrs. Coating time was 4.5 minutes at an operating potential of 700-1,200 V and a current of 15 mA. Although measurements were not made of its thickness, the gold-palladium coat was not deemed excessive for the desired magnifications of 50 and 1,000. Seeds were scanned in an AMRAY 1200b SEM. Accelerating voltage was 15 kV, final aperature size 100 µm, and a working distance to the specimen of 15 mm. In most instances, the external surface of mature testas was photographed at 50 and 1,000 magnifications.
All data were recorded in an ASCII text file in DELTA format (Dallwitz, 1980Dallwitz, 1980:
Dallwitz MJ. 1980. A general system for coding taxonomic descriptions. Taxon 29:41&-46.
; Dallwitz et al., 1999) on an IBM-compatible microcomputer. DELTA format is a free-form, unlimited data-coding format which accepts multistate, numeric, and text characters and provides for linking of image files to both characters and taxa. Once recorded, the data were checked for syntax and maintained using the DELTA software system (Dallwitz, 1980Dallwitz, 1980:
Dallwitz MJ. 1980. A general system for coding taxonomic descriptions. Taxon 29:41&-46.
; Dallwitz et al., 1999) developed by Michael J. Dallwitz formerly with the Division of Entomology, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Canberra, Australia. The final character list had 318 characters, which included 157 fruit characters, 128 seed characters, and seven distribution characters. The illustrative materials, drawings, photographs, and SEMs were individually scanned. The images were assembled into files using Adobe PhotoShop, and attached to the database.
Authors: J.H. Kirkbride, Jr., C.R. Gunn, A.L. Weitzman, M.J. Dallwitz, K.R. Thiele
Content last updated April 2003
Released April 2024 on idtools.org
