gravity, trees, severian

Here is something that I think is interesting: the Caesalpinia sappan that Severian runs into in the Jungle garden is described as "Lianas half obscured the entrance, and a great tree, rotted to punk, had fallen across the path a few strides away. Its trunk still bore a small sign: Caesalpinia sappan" (Shadow and Claw 123) It is described as a great tree, yet here is my definition from a botany page: "- Small tree up to 5 m high with scattered spines. The compound leaves are 50 cm long, with 20-30 shiny leaflets. Flowers yellow, 2.5 cm in diameter with densely wooly filaments. Fruit is hard, indehiscent, shiny pod about 7 cm long. - Widely distributed in the Philippines at low and medium elevations, often in dry thickets. - Propagated by seeds and cuttings." Is there a difference between "Small tree" and "great tree"? or is it just a matter of "scale"? At the beginning of the next chapter Severian says "a new sound - a new voice - came from some red world still unconquered by thought". (Sounds like mars or something, doesn't it?) when he describes the cry of the Smilodon. The jungle garden is quite a bit warmer than the other botanic gardens, but I have always assumed this is because it was in the past. Is there any possibility that the Jungle Garden is not actually on "Urth", but is some place else? I don't know. Marc