[shortened – 21/10/2016]
I thought readers might be curious to know how, since I date to about the 2ndC BC the first enunciation of most botanical images in Beinecke 408, and they have bewildered everyone since 1912, I can suppose they were understood in medieval Latin Europe when our manuscript was made. They were not understood in the seventeenth century  and are not now – so why should any fifteenth-century Latin have understood them better, or valued them enough to bother copying them onto vellum; why would he not use as his exemplar some Latin work whose pictures were more intelligible.
First, I do not think there are any Latin plant-books with this manuscript’s range or series, nor any that use the style of construction used here, and there is no indication that the Voynich botanical imagery’s content, any more than its style, derives from the Latin herbals. So rarity alone might explain its being copied. If memory remained of when the pictures were first formed, reverence for the antique might also explain it. 
I would expect that so long as someone had first explained the imagery to a medieval Latin the very practical purpose of these pictures would assure ready apprehension by any whose lives and occupations made them familiar with the same practical and technical matter. The barrier to understanding is less the pictures’ subject matter than their having been first formed in a very different culture, and while a different set of practices governed the way information was expressed in graphic form: what we call generically, “stylistics”.
To illustrate how the gulf might be bridged, and the manuscript’s content valued thereafter, I will suppose that the picture on folio 5v – whose theme is “protection for the ship” – was known to a particular group of thirteenth-century Genoese and explained to them.
These were not scholars nor scribes nor missionaries nor aristocrats, but shipwrights and mercenaries invited to Baghdad in 1290 AD, to assist the Il-Khan Arghun in his projected war against the Mamluks of Egypt. Below, an example of the coin in which they may have been paid.
Seven hundred of those Genoese went directly to Baghdad, but two hundred stopped at Mosul, where they spent the winter building two sea-going ships. If any Latins were in a position to appreciate folio 5v, then, it would be they. “Protection of the ship” was something they understood at many levels.
That isn’t the only reason I take these Genoese as example. There, in Mesopotamia, and just a century before, a Yemeni artist had produced botanical images using conventions for some of the plants’ roots that are closely akin to those employed for some stylized roots in the Voynich manuscript. As I’ve constantly said, the Voynich root-mnemonics (or ‘pictorial annotations’) appear to have been mostly added during the third chronological phase (i.e. c.1150 -).
I’ve treated the point in earlier posts, but above are shown again two of the comparative illustrations. If readers notice any other Voynich sites repeating the same, and referring to the Mashad Dioscorides in this context, I’d be obliged for the information; some are evidently vague about the line between plagiarism and fair use.
And, finally, I’ve chosen the Genoese shipwrights because they served a Mongol ruler, and the ‘Mongol century’ sees the last substantial additions made to the matter now in Beinecke MS 408. (I am in all this excluding the text’s written part, since we do not know when it was first composed).
Below, a detail from the manuscript shows a figure dressed in a Mongol costume – as earlier explained and illustrated: here and with historical context here. (Again, I am obliged to mention that this original observation and discussion may be found on other sites, without proper acknowledgement of the source). 
As we’ve said, the single theme informing folio 5v may be expressed as “protection of the ship”, but the cue to that theme, the Dioscuri as pictured here, would have been an emblem as obscure to those Genoese as to any who’ve seen the folio since 1912. Hellenistic ideas about the Dioskuri were not transmitted through medieval Latin culture and a majority of those currently attempting to explain the imagery look no further.
They might have known the legend of Dioskurias’ founding, however, thanks to Isidore, and some may even have known the place. It was thirty years since the Treaty of Nymphaeum gave Genoa leave to establish trading ‘colonies’ in the Black Sea, and if the local name for Dioskuras was then, as it is now, Sokhumi: “Yoke Elm“, that link between the town, the tree and the Dioscuri would have been intelligible – had the elements informing the image been explained to them.
Already the Genoese had a presence in Trebizond, next to the Colchian lowland where the Sokhumi or ‘Yoke Elm’ is naturally abundant and occurs together with the Field Elm (Ulmus minor),  both woods being familiar and much sought after by shipwrights of the Mediterranean and, in my opinion, the chief reference of the botanical image on folio 5v.
Modern taxonomic description has the Yoke Elm (Carpinus betulus) a member of the beech family, but in earlier times it was perceived as an elm, and since this older perception informs folio 5v, I’ll use the older term. 
Its open habit and its low-growing and slender limbs are here taken to define the group:
The original enunciator, as is usual, paid closest attention to the plant’s habit, and then to its leaves and petioles, and notes accurately as ever whether these occur alternate, opposite, or both. His familiarity with the tree is clear; one detail even captures nicely the way new leaves of the Yoke elm can appear like drooping wings. The serrated leaves are right, as you’d expect, and are a characteristic in common with the Field Elm (Ulmus minor).
Quite unlike the habit of Latins, medieval or modern, and unlike herbals derived from the Dioscoridan lineage, imagery in the Voynich botanical folios consists of a group of plants related by proximity in habitat, having comparable and complementary uses, and does not regard the flower as definitive (save for the anomalous folio 9v).
The flower may be omitted, or represented by some regional, conventional, stylized form.  It was enough for the first enunciator that those of his own time and community could recognise the reference – one cannot suppose he expected it to be read more than two millennia later, and half a world away. The flowers, in this case, are presented almost poetically, and both may indeed be fairly described as “starry”.
For most carpenters and woodworkers, the timber of the Yoke Elm is near-useless, intensely hard and difficult to work. For the shipwright, though, its short dowel and straight pegs were invaluable.
The iron-hard wood made fire-sticks from which new fire could be produced by friction after period of rough weather – when all flames were extinguished. A similar use, as we’ve seen, made the elm valuable. Yoke-elm pegs served to fix the planks of a deck. Metal nails will shrink expand and rust and loosen, but these were hard as iron and very stable. For rowlock pins, pegs to hold rigging tight and even for gear-pins, there were was nothing better.  And idle shipmen might carve them into chess-pieces in lieu of ivory.
The Field Elm (Ulmus minor) was another hard wood too, but one having other qualities. Where the other was notoriously rigid, this was pliable. Its resistance to water decay is exceptional and sees it still used today, as anciently, for underwater piles, water-pipes and barrels. It is a timber which positively likes to be kept wet and (I’ve checked) it doesn’t mind salt in the water.
Timber from U.minor was recommended for exactly the sort of tools needed by those Genoese workmen in thirteenth century Mosul. It was recommended for levers and for mallets, and to make the handles of tools constantly in use. Unlike timber from C. betulus, it could be turned on the lathe and in addition it served for the bows – and the stocks of those crossbows for which the Genoese were already famous, not only as wielders but as manufacturers.
Bows and crossbows have an immemorial association with the ship and were its quintessential ‘protection’, not only against human beings but because birds which perched on the deck or rigging could be brought down and used to provide fresh meat.
This connection between the bowman, the ship, its crew and cargo, would have seemed “common sense” and inevitable to the Genoese and was a near-symbiotic relationship that survived no less than six millennia in the Mediterranean world. The two elms – the rigid and the bending – were part of that tradition for millennia.
The Voynich manuscript includes one rare illustration of that relationship.
The type of crossbow given the Voynich archer is evidently one designed specifically for use at sea; it included a roll-lock inserted into the top of the stock, and is a type of bow so rarely attested that at present archaeology has produced only two late examples. There may be other representations in medieval manuscripts, but they have passed unnoticed, as this in Beinecke MS 408 had been until recently, memory of the type having been all but lost to history.
Before the Padre Island finds,  we had no reason to suspect the existence of such a type, and before I wrote on the subject, it had not been brought to the attention of Voynich studies. I regret that the person who did first notice the point of the archer’s hands is determined to remain anonymous  and I am obliged to have others credit my published work rather than his observation. Whether any other manuscripts made in Europe contain more images of such bows must wait on some researcher’s willingness to investigate. At present its earliest use is unknown.
Nor do we know what timbers the Genoese used in Mosul, but had the image on folio 5v been shown and then explained to them, including the significance of each ‘pictorial annotation’, they would surely have understood the parts and the reasoning of the whole.
In the region around Mosul no suitable timber is found for ship-building, something that led Richard to speculate  that the Genoese brought the timber with them from further west – in which case they would have had cedar and fir. But that abundant source for the two elm(s) lay no further north than did the Mediterranean coast to the west, and since the Colchian lowland was already under Mongol control, Arghun could have had delivered to Mosul whatever timber the Genoese preferred. From the north a road began in Tanais, passed through Dioskurias by the Colchian lowlands, and thence south towards Mosul. So in either case, cartage was possible.
The obvious question, though, is: “If Mosul offered no natural supply of ship-building timbers, and was further from the sea than Baghdad, why did the Genoese stop there to build their ships?” To which the answer is, once more, …. “protection of the ship”.
Mosul’s reserves of bitumen were the marvel of the ancient, classical and medieval world… and a hull painted with bitumen deterred the teredo.
NOTES: see following post.