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Anthers and Stigma of Zygocactus truncatus

Click on either of the images to see the fully expanded version.












Fig. 1 (above) is an extended focus micrograph of an isolated anther.

The stamens of Z. truncatus carry the same dense magenta colour of the rest of the flower, although the pollen grains themselves do not.  The anthers are relatively small and numerous - a common feature among the Cactaceae.  Fully dehisced, they are 'bullet' shaped, ca. 800µ long and ca. 400µ wide at the widest point.

The pollen grains themselves are unpigmented, spherical and ca. 50 - 60 µ diameter.

The stigma (Fig. 2 - below) has a rather unusual shape - a ribbed, tapered cylinder.  This stigma form is not shared by its cousin the 'Easter Cactus' (Schlumbergera gaertneri), but curiously it is shared by the Fuchsias, which although not remotely related to the cacti, evolved in the same American sub-tropical forest environment.  Given that this morphology results in a relatively low surface area to volume ratio, it's not at all obvious what benefits it offers.

The example in Fig. 2 has a number of pollen grains sticking to it.











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