The nymphs are possibly inspired from Dante manuscripts

[Jorge_Stolfi]

To me it looks like the author simply had no general idea what plants looked like IRL, so he made fatal flaws when interpreting drawings.

What kind of person has no idea what plants look like IRL? This seems to be a very strange person, indeed.

If you asked people today to draw from memory a detailed picture of some plant that is supposedly well known -- like a dandelion, a rose bush, a carrot or corn plant, even a palm tree -- eight of ten of the results would be as flawed as the VMS plants. 

Our memory is a bizarre tool.  You think you can see in your mind a perfectly clear image of the staircase in your home, or the building of your school, which you have seen thousands of times from all possible angles.  But try to bring up that mental image and count the steps in that staircase, or the windows in that building. You will find that you can't. (Unless you are one of very few people with "photographic memory".)  And it is the same with other objects, like plants.  

All the best, --stolfi

PS.  One of the books I most enjoyed reading was Cosmicomics by Italo Calvino.  I can see in my mind a clear image of the book's cover,  the layout of the pages and chapter headings, even the fonts.  I remember all the stories and even some memorable sentences.  Only problem is, I cannot remember whether it was the Italian original or the English translation ...