**5. Conclusions**

There were vibrations associated with calcium carbonate in the P of *Ariocarpus retusus* subsp. *trigonus.* The calcium carbonate reported here increases the diversity of biominerals in cactus. The hydration state of calcium oxalate is conserved in the different tissues that were studied in the stems of the Cacteae species. Both calcium oxalate and silica bodies were present in the same species but in different tissues for *Echinocactus texensis*. The presence of silicate peaks belonging to species such as *Astrophytum asterias* and *Mammillaria sphaerica* opens the opportunity to study the role of silicates in the physiology of Cacteae species.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2073-4352/10/6/432/s1, Table S1. Assignment of FTIR absorption bands of biominerals extracted from tissues of Cacteae species.

**Author Contributions:** T.T. and A.D.l.R.-T. designed the work, T.T. collected the plants, A.D.l.R.-T. and A.M. performed the lab work and prepared the figures, A.D.l.R.-T., T.T. and A.M. analyzed the data, A.D.l.R.-T. wrote the original draft. All authors reviewed and edited the manuscript. All authors have read and agreed to the published version of the manuscript.

**Funding:** Funding for this research was provided by Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica, Universidad Nacional Autónoma de México (PAPIIT-UNAM); grant no. IN205419 to TT and Consejo Nacional de Ciencia y Tecnología (CONACyT), grant no. 703332 to ADR-T.

**Acknowledgments:** ADR-T thanks Posgrado en Ciencias Biológicas (UNAM) and AM & TT thank to Rubén San Miguel-Chávez for helping us to use the FTIR.

**Conflicts of Interest:** The authors declare no conflict of interest.
