Key to the species and varieties of Rafflesia

1Ramenta short, more or less pustulate, only a few millimetres long, in some cases clavate
1'Ramenta more than 2.5 mm long
2Flowers 15-20 cm in diam. Opening of diaphragm (orifice) relatively wide, leaving the lower inner side of the flower tube exposed to view from above. Anthers c. 15
2'Flowers at least 25 cm in diam. Orifice of diaphragm too small to expose the inner side of the flower tube. Anthers 20-40
3Flowers (15-)30-60 cm in diam. Rim of disk steeply raised. Anthers (25-)32-40. Ramenta very short knobs
3'Flowers 26-30 cm diam. Disk rim only slightly raised. Anthers about 20
4Perigone lobes and diaphragm in general red or orange throughout, including the warts. Diameter of flowers on average 20 cm (15-30). Ramenta slender and swollen at apex
4'Perigone lobes with white warty blots, or disk with many processes, or flowers larger than 30 cm diam. (R. micropylora)
5Disk of flowers totally smooth or with up to 8 processes, rim not raised. Anthers 15-20
5'Disk with c. 25 processes, rim raised. Anthers 20
6Orifice of diaphragm angular or slightly lobed, very small compared to the size of the flower, 3-9 cm in diam., too small to be able to count the c. 15 processes. Ramenta often branched and apices of branches globular, swollen. Flowers 30-60 cm diam. Warts on perigone lobes reddish
6'Diaphragm opening relatively larger
7Apices of the ramenta either more or less distinctly swollen or crateriform
7'Apices of the ramenta not distinctly swollen
8White warts across the base of the perigone lobes very large, 4 or 5 only. Ramenta slender, apices swollen. Anthers c. 20. Diaphragm with only one basal ring of dark-brown warts
8'White warts across the base of the perigone lobes more than 5. Diaphragm with several concentric rings of warts
9White warts across the base of the perigone lobes 10-12. Some ramenta with swollen, others with crateriform apices. Anthers c. 30
9'White warts across the base of the perigone lobes 7-9. Ramenta slender, all with swollen apices. Anthers 20-25
10White warts in tangential direction about halfway along the perigone lobes relatively covering less space than the red parts, c. 8 in number
10'White warts on perigone lobes more numerous
11Flowers c. 70 cm in diam. White warts on the perigone lobes very small, covering far less space than the red-coloured part. Anthers (20?-)24-30
11'White warts on the perigone lobes covering more space than the red-coloured part
12White warts across the base of the perigone lobes 5 or 6(-10)
12'White warts across the base of the perigone lobes more than 10
13Flowers up to 80 cm diam. Lower face of the diaphragm with ramenta. Anthers 26-38
13'Flowers (16-)25-37.5 cm diam. Lower face of diaphragm without ramenta. Anthers c. 20
14Larger white blots on perigone lobes interspaced with numerous small ones. Circular blots on diaphragm contrasting, isolated and with broad dark-brown margin
14'Larger white blots on perigone lobes not or very sparsely interspaced with smaller ones. Circular white blots on the diaphragm little contrasting with their surrounding tissues, often more or less connected in a network of dark reddish bands and with only a thin dark redbrown margin
15Ramenta covering the inner side of the flower tube from the rim of the diaphragm downwards to the outer annulus
15'Ramenta missing in a zone above the outer annulus at the base of the column.