Sieve‐element Plastids of Fouquieria, Frankenia (Tamaricales), and Rhabdodendron (Rutaceae), Taxa Sometimes Allied With Centrospermae (Caryophyllales)

Summary An ultrastructural investigation of sieve‐elements of nine species of Tamaricales (including Fouquieria and Frankenia ) demonstrated plastids of the starch‐storing S‐type. Sieve‐elements of Rhabdodendron (Rutaceae) contained P‐type plastids with a single polygonal protein crystalloid besides starch grains. In these respects all these species are unlike the specific P‐type plastids characteristic of the Centrospermae.