Ein Beitrag zur Anatomie und Morpbologie von Phyllactis Persoon

Abstract

Summary The species of the high-andean genus Phyllactis Pers. are pachycaul rapegeophytes and chamaephytes possessing a proliferating apex and a leaf rosette with spiral phyllotaxis. They have shoots usually without vegetative branching ( P. rigida ) or are branched frequently ( P. pulvinata ). Young plants of P. rigida have a spirodistichous phyllotaxis. In adult plants the sheaths of neighbouring leaves are connected at their bases. The shoot of P. dorotheae bears a firm collar which is several millimeters thick and consists of remnants of dead leafbases and soil particles pasted up with resinous lipids. These lipids are produced in parenchyma cells of the pith, cortex and mesophyll. They can be transported apoplasmatically and are plentifully present in the intercellular spaces. In the vascular system of adult plants of the species investigated bipolar bundles possessing an internal phloem and xylem develop from collateral open bundles and, in zones of vegetative ramification, they can be splitted in parts often hadrocentrically shaped. Rhexigene intercellulars occur between the pith and the internal phloem of bipolar bundles and between neighbouring bipolar bundles and in the cortex. Other intercellulars develop in the cortex. Therefore the older secondarily thickened shoot is strongly cleaved modifying into a rhizome where groups of bipolar bundles are often arranged in rings. The specific development of bipolar bundles in species of Phyllactis is compared to that of other Valerianaceae . Specific anatomical characters are reported: Sieve elements radially extending are found in the shoot of P. rigida . In the shoot of adult plants tracheids and fibers are missing completely, both in primary and secondary xylem. The short vessels always have scalariform pits and are mostly simple perforated. Poorly developed transfer cells are observed in the primary xylem of young plants and seem to be frequent and well developed in the primary phloem. They are missing in the secondary xylem and phloem.