One group of Coryphantha spp. (subgenus Neocoryphantha) always produces extrafloral nectary glands. These occur in the groove or in the axil. The nectary glands are round and often bordered by a narrow margin of woolly felt. Their colour varies from red through orange to yellow. In the vegetative period they secrete a transparent, sugar-containing nectar.
The second group of Coryphantha spp. (subgenus Coryphantha) has the potential to produce optional nectary glands. These are found directly behind the spiniferous areole in the groove and appear during the flowering period of the plant only, otherwise they are invisible (see Plate 2, photos 1-4).
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