FURTHER-STUDIES OF THE SIEVE-ELEMENT PLASTIDS OF THE CARYOPHYLLALES INCLUDING BARBEUIA, CORRIGIOLA, LYALLIA, MICROTEA, SARCOBATUS, AND TELEPHIUM

The sieve-element plastids of 69 species of the Caryophyllales were investigate by transmission electron microscopy. All contained the specific subtype-P 3 plastids characterized by a peripheral ring of protein filaments. The presence or absence of an additional central protein crystal and their shape being either polygonal or globular as well as the average sizes of the sieve-element plastids are useful features in the characterization of some families. - Barbeuia contains sieve-element plastids that confirm its placement within the Phytolaccaceae. Lyallia differs from Hectorella by including small starch grains in their sieve-element plastids, which otherwise by their globular crystals negate a closer connection to the Caryophyllaceae. The lack of a central protein crystal in its form-P3fs plastids places Microtea best within the Chenopodiaceae. Sarcobatus, a so far uncontested member of the Chenopodiaceae, contains form-P3cf plastids, i.e., including a central crystal not found elsewhere in this family. Telephium and Corrigiola, shifted back and forth between Molluginaceae and Caryophyllaceae, have form-P3cf(s) plastids with a polygonal crystal which favor their placement within the Caryophyllaceae.