Espostoa (Vatricania) Guentheri have Unusual Cephalia or Pseudocephalia

Abstract: Espostoa (Vatricania) guentheri is a peculiar putative Espostoa, having some traits in common with Espostoa sensu stricto (cephalia in which many or most epidermal cells produces a spine, bristle, or trichome), some traits in common with Thrixanthocereus (cephalia with bristles instead of hairs; patches of epidermal cells in the cephalium that lack spines, bristles, hairs or trichomes), and some unique traits (gradual transition to cephalium formation; disjunct habitat). Gradual cephalium formation in E. guentheri is common, but not universal, which might be either because Vatricania is not closely related to Espostoa or that Vatricania is of hybrid origin. E. guentheri may have a pseudocephalium, rather than a true cephalium, with the reproductive part of shoots in subgenus Vatricania being morphologically intermediate between those of subgenus Espostoa and subgenus Thrixanthocereus.