Pollen morphology of Raphionacme (Periplocaceae)

A tribal classification of the Periplocoideae (Apocynaceae)

“…2). The tetrads are uniform in structure and have three to six (0) pores per grain throughout the family except in Raphionacme that has six or more (1) pores per grain (Verhoeven & Venter, 1988). R. abyssinica Chiov.…”

Pollinium structure in periplocoideae (apocynaceae)

“…Throughout the Periplocoideae tetrad morphology is very similar. Raphionacme is the one genus that can be distinguished by its multiporate pollen grains (Schill & Jäkel 1978, Lebrun et al 1984, Verhoeven & Venter 1988) in contrast to the 4-6 pores in the other genera. The exine structure, consisting of a solid stratum (tectum) subtended by a granular stratum, has little variation within the Periplocoideae tetrads (Verhoeven & Venter 1993, 1994aVerhoeven et al 1989).…”

“…In Streptocaulon the inner walls are reduced to a thin exine layer and intine. The inner walls have been described as perforated (Verhoeven & Venter 1988) and, also, as thin perforated or with larger openings penetrated by crosswall cohesions (Nilsson et al 1993).The inner walls only appear perforated in acetolysed material. The pores are actually wall bridges for cohesion (Knox & McConchie 1986), consisting of intine and granular stratum.…”

“…Historically the Periplocoideae was classified in the Asclepiadaceae (Schuman 1895), but was given family status by Schlechter (1924). Within the recent past the Periplocaceae was treated as a family (Verhoeven & Venter 1988Venter et al 1990, Dave & Kuriachen 1991, Kunze 1993, Liede & Kunze 1993, Nilsson et al 1993, Swarupanandan et al 1996 or subfamily (Dannenbaum & Schill 1991, Goyder 1992, Civeyrel 1994. The families Asclepiadaceae and Apocynaceae have been kept separate in most systems.…”

“…In the past, the pollen morphology of genera such as Raphionacme (Verhoeven & Venter 1988), Tacazzea Decne. and Petopentia Bullock (Verhoeven et al 1989), Ectadium E. Mey.…”