SCANNING ELECTRON MICROSCOPE STUDIES OF THE SPINES AND GLOCHIDS OF THE OPUNTIOIDEAE (CACTACEAE)

The genera of the Opuntioideae are surveyed for certain spine and glochid structures. Retrorse scabrosity of both spines and glochids is regarded as characteristic of the subfamily. Critical differences are noted in the bases of the glochids, flattened fish-tail forms being found in Opuntia, Nopalea, Cylindropuntia, Tephrocactus, and Tacinga, and enlarged, rounded, hollow forms in Pterocactus and Grusonia. Small unflattened bases are found in Pereskiopsis and Quiahentia. Minor variations of the flattened form of glochid base are noted in Cylindropuntia, Austrocylindropuntia, and Opuntia brasiliensis; and the possible significance of the structures is discussed.