You know what Thomas a Kempis said.
Oh to be one of those to whom truth communicates itself directly-- not by means of symbols and words, whose meaning changes with time, but in its very nature! Our own estimate, our own way of looking at things, is always putting us in the wrong, by taking the short view. And here we are, splitting hairs about all sorts of mysterious problems which do not concern us-- we shall not be blamed, at our judgement, for having failed to solve them. Strange creatures that we are, we forget the questions which really matter to us, matter vitally, and concentrate, of set purpose, on what is mere curiosity and waste of time. So clear-sighted are we, and so blind!
Why should we be concerned to divide up things into “classes” and “families”? We get away from all this tangle of guess-work, when once the Eternal Word speaks to us. From him alone all creation takes its origin, and thereofre all creation has but one voice for us; he, who is its origin, is also its interpreter. Without him, nobody can understand it, or form a true judgement about it. Until all things become One for you, traced to One source and seen in One act of vision, you cannot find anchorage for the heart, or rest calmly in God…
The point that was being made was that you’re looking at a classification system that was designed to classify physical objects, and are trying to philosophize it. I can create any classification system I want-- the Dewey Decimal system or the LCC or the Universal Decimal System or something homegrown. So just like Dewey Decimal can categorize things out to the third or fourth decimal, if desired, it doesn’t take into account whether a book is red, or is over 500 pages, or whether it was printed in 1995, whether it makes me cry, or whether it sold over a million copies.
So, the same thing is true with plants. The idea of the “plant kingdom” was founded on physical characteristics. The first one is having a cell wall— which is why you have a Fungi Kingdom, because fungi aren’t categorized as plants, which is why algae isn’t a plant. Second, plants have cuticles. And third, plants make their own food-- even if they may supplement it eating other organisms, like a Venus flytrap, which has photosynthesis, but also eats insects.
Things like discovering how plants communicate with each other is still a baby science. There’s a ton we don’t know.
So until you have the ability to fully know the powers and faculties of all plants and all animals, it’s just a sort of speculative exercise… which is okay for philosophy… but you’re ultimately trying to make a classification system that was designed to account for X also take into account Y… which we have incomplete information about.