Jansy Mello: I assumed incorrectly that there was a trap in Van's flow of associations. From an internet site I learned that, for the tree, there is an "alternative Latin designation 'Salisburia adiantifolia', proposed to honour Richard A. Salisbury" and that it "presumably refers to the generic name Adiantum of the maidenhair fern, though this is odd, since the fan-shaped leaves are not a defining characteristic of the genus, and I don't believe 'adiantum' itself has anything to do with the shape at all."

Van's "poor Salisburia" could be related to Salisbury's scientific fate, marred by accusations of plagiarism and for refusing to accept the Linnean system (I remember Nabokov held particular restrictions to it, too). Still following Wikipedia:"The censure was later reported as,'there was a tacit understanding on the part of the botanical leaders of the period, including Brown, Banks, and Smith, that Salisbury's botanical work and names should, as far as possible, be ignored' —Journal of Botany, 1886, p. 297."

Van's "Salisbury’s adiantofolia, Ada’s infolio, poor Salisburia..." might not have been so innocent, either - if we consider it as a reference to Ada's "maidenhair". There's a line in Lady Chatterley's Lover (I know VN disliked most of DH Lawrence's works) that was quoted in one of the articles about the Gingko:

"[Mellors says] 'Look at Jane, in all her blossoms!...Pretty little Lady Jane'... and kissed her maidenhair."

I've been wondering about John Shade's Gingko Biloba poem. Could Nabokov have written the lines long before he inserted CK's notes about it? VN might (pure conjecture...)have used the spirit of the Japanese haiku then, focusing solely on the botanical image. Later on, when Kinbote appropriated it in his notes, the similarly named poem by Goethe would have served to add a hidden twist to it..