Pilosocereus collinsii

References

1. [1]The Cactaceae — Britton N.L. & Rose J.N. · The Carnegie Institution of Washington; Washington. · 1920 · http://www.biodiversitylibrary.org ↩︎An immense work in 4 volumes. Many of the botanical names are out of date, of course, but the book contains a wealth of information about the plants. It can be downloaded from the Internet.
2. [2]IUCN Red List of Threatened Species — http://www.iucnredlist.org/ ↩︎A list of plants under threat and facing possible extinction, usually with brief details of the threats and information on habitat.
3. [3]Cacti Biology and Uses — Nobel, Park S. (Editor) · University of California Press; Berkeley, California · 2002 · ISBN 0-520-23157-0 ↩︎A lot of information about the uses and cultivation of Cacti native to central Mexico