**4. Conclusions**

*Syngonium* is a very reactive species that is easy to cultivate in vitro. Different balances of plant growth regulators can be used to successfully initiate meristem cultures and the first stages of micropropagation of this species. Moreover, the different vitamin and mineral compositions tested could not completely impede de novo shoot development. All manner of morphogenetic programs have been studied since 1976, including shoot formation, rooting, callogenesis, protocorm formation, and embryogenesis. The main basal mineral medium composition used was MS62. Based on our histological analysis of calli originating from MS62 and N69, some obvious differences were observed in their structure. Thus, we observed the constant positioning of xylematic elements in the callus zones adjacent to meristematic and nodule-like areas, as well as organogenetic centers. Additionally, protocorms of *Syngonium* were identified with N69, and their formation was associated with very well-developed tracheary elements, constituting a novelty of this study. Conversely, the organogenetic centers observed in the callus originating from MS62 revealed less-differentiated xylematic elements, but these were also constantly in the presence of and closely connected with meristems, roots, and shoots. Based on these observations, the culture medium influences the development of specific areas in the callus structure. Each of these areas may contain pluripotent and totipotent cells, and their specific arrangement inside the callus can further support organogenetic processes, including de novo shoot formation. The addition of cysteine to the culture medium in the pre-acclimation phase can further support the success of de novo shoot development for acclimation. Moreover, lessons learned from all experiments performed on *Syngonium*—including the principles applied to implement industrial-scale micropropagation—may further support the production of phenolic compounds relevant for in vitro systems at the industrial scale. **Author Contributions:** Conceptualization, M.-M.A. and C.S.S.; methodology, M.-M.A.; validation, M.-M.A. and C.S.S.; formal analysis, M.-M.A.; investigation, M.-M.A.; resources, M.-M.A.; data curation, M.-M.A.; writing—original draft preparation, M.-M.A.; writing—review and editing, M.-M.A.; visualization, C.S.S.; supervision, C.S.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** This paper is dedicated to the memory of Aurelia Brezeanu, the mentor in the formation of Maria-Mihaela Antofie, who provided much counsel and inspiration to us both, for her pioneering work, valuable contributions, and untiring efforts in developing the science of plant cell, tissue, and organ cultures in Romania from 1970 to 2022.

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