Über den Feinbau der “verzierten” Tüpfel bei der GattungPlathymenia

Abstract

Replicas from radially and tangentially cut and split sapwood sample sof Plathymeinia foliolosa and Plathymenia reticulata were investigated by electron microscopy. The electron micrographs were compared with the aspects of sections and veplicas as seen with the light microscope, using bright field and phase contrast. It was possible to demonstrate the structure of the vascular vestured pits as represented in fig. 10 and to obtain datails on the fine structure of the different parts of the pit cavily. The bordered pits in the vessels are vestured both at the outer and inner apertures. The appearance of the vestured apertures is due to processes which are attached to the borders of the apertures. They vary according to number, size, and form and can be characteried there by main structural types: simple (papilloid), coralloid, and distincltly brauched. The electron microscope reverals no fine structure of the processes; they appear to be amor phous. The pit canal crosses the secondary wall mostly without alterations in diameter. The wall appears to be smooth and no processes were observed. On the pit chamber coated by the tertiary wasl smaller processes may occur, surrounding the verstured aperture. To the periphery, wartliary wall of the vessels. The corerlation between the amorphous wart structure and the processes was emphasied and the proballe analogy of the two structures, both covecring the tertiary wal, was discussed. The pit membrane consists of the primary walls of the adjacent cells with the middle lamella in between. The loosely interworen microfibrils, typical for the primary wall, were clearly visible. Oecacionally, “blind” pits were found, meaning that these pils had no complement on the adjacent cell elemnt. In these cases, the pit membrane was corerred by the secomdary wall thereby closring the pit chamber completely. In the half-bordered pit pairs of the paratracheal and ray parenchyma, only the bordered pits of the trachery elemnts were found to be vestured. Vestured pits in the cessels are characteristic for the two species of Plathymenia and may be considered as jeature of the geuns. Distinuctice for the species are the coalescent, slitlike aperfares in Pathymema joliolosa as well as the prevailing of the simplet papilloid) and coralloid strunctures of the processes in Plathymenia retiulata