Though Louis Nicolas underwent the rigorous education associated with the Jesuit religious order, he never had any formal training in botanical illustration. Some of the plants are poorly represented, and have proven to be difficult to identify, the illustrations generally lacking consistency in their representations of plant anatomy. In a pre-Linnaean scientific world, Nicolas used Aristotelian explanatory framework to relate his accumulating observations about plants to the authority of religion-tinged ancient knowledge. Additionally, there does not appear to be any explicit criteria for the classification of the plants in the "Codex", but it can be deduced that the author ordered them by size, starting from smaller herbs, to fruits and then trees.