An important indication of what I have posited as transmission of matter now in MS Beinecke 408 from the eastern to the western side of the Mediterranean, in the mid-twelfth to mid- thirteenth centuries, is offered by the style in which plant-roots are depicted in the botanical folios.
The custom by which marsh-loving and aquatic plants are denoted by being set on a flat-bottomed ‘island’ from which the roots descend in parallel or near parallel lines, is one having an origin in the east, and rarely understood or intelligently employed elsewhere. The habit occurs on Asian ceramics throughout the centuries and remains a convention of Asian art today. In regions where Asian style was both admired and absorbed by proximity, such customs did occur in other contexts and in other media including textiles and manuscript art.
The examples shown here are (left) a ceramic fragment from pre-colonial Singapore;(below, left) detail from folio 46r in MS Beinecke 408 and (below, right) detail from a thirteenth century copy of Dioscorides’ materia medica made in upper Mesopotamia and later donated to a shrine in Mashhad where it remains.
As you see, all three of these examples use the same convention to the same purpose and with similar facility. Each intends to inform the reader that the plant is one from an aquatic or marshy habitat.
In each case, too, the draughtsman is able to employ the motif with obvious consciousness of its meaning, and to use it with easy flexibility (somewhat less so in the case of the Mashhad Dioscorides than in the other two) Such things tell us that the habit was a well-known custom, in regular use in the draughtsman’s native region, and is not here merely as a result of copying a foreign exemplar.
Each of the three original draughtsmen spoke (as it were) dialects of a common visual language.
The provenance of the Mashhad Dioscorides is precisely known. During the twelfth century, in Hisn Kafiya and Mayaffariquin, fresh translations of Dioscorides’ Materia medica were made into Arabic. Of these, the first type is preserved in Bib.Nat. Arab.4947, and the second in the Mashhad Dioscorides.
None dispute that the text was gained by translation from a Syriac version of the Greek text, but the drawings and paintings reflect contemporary practice. Another leaf, now in the Baltimore Museum, shows paintings that are the work of a Yemeni Christian according to Florence Day, whose opinion remains the standard. So – without going into more complex matters still debated among scholars – we can surely say that the thirteenth century and the eastern side of the Mediterranean is most appropriate for this style of botanical drawing which has so bewildered a century of persons attempting to find correspondences between the Voynich botanical folios and anything in the western herbal corpus and its traditions. 
Another item tending towards the same conclusion is the evident independence of those three examples. It clear that the convention used to mark an aquatic or marsh plant is a convention in itself; it is applied not just to one such plant, but to any for which it is appropriate. The Asian plant is believed meant for duckweed; that in the Mashhad Dioscorides for the water Iris; and that in folio 46r of MS Beinecke 408 is, in my opinion, meant for one of the mangroves species, presumably one with leaves larger than the usual and perhaps one of the Heritiera, valued for its timber(e.g. here); its flower and habitat are drawn closely similar to a mangrove group pictured on folio 43r. 
The style in which the ‘water-habitat’ motif is drawn in each case also shows that the draughtsmen were familiar enough with its significance to employ it easily and as they were evidently accustomed to do; each form is distinct yet all say the same. This tells us plainly enough that we need not expect – and comparisons clearly do not allow – an argument that imagery in MS Beinecke 408 has been copied from the Mashhad manuscript. Rather, the images in MS Beincke 408 took their form in a region where use of the motif was commonplace.
In the Latin herbals, no equivalent occurs, nor do we see an equivalent ease when Latin scribes copy the Arabic works translated for them, most often, by multilingual Jews.
The ‘waterside plant’ token is not the only motif common to MS Beinecke 408 and the Mashhad Dioscorides. Another is a twining form near-identical in both cases. It strengthens the probability that these folios in the Voynich manuscript did not develop after the 13th century and took that final form in the eastern world and are no invention of fifteenth century Latin Europe.
The twelfth and thirteenth centuries witnessed great upheaval and distress in the Jazira and the Levant, not least due to earthquakes which destroyed cities and forced populations to migrate. In 1170 an earthquake had affected the eastern Mediterranean, including Antioch and Tripoli. Writing of it later, Benjamin of Tudela reports that more than 20,000 had perished from it in the Holy Land. (Not that Italy was much luckier during the same centuries).
To social, military and natural disasters, we must attribute that migration westwards which now occurs and leaves its evidence in newly-seen styles and customs in the west. It is now that the use of micrography first emerges among the Sephardi and Ashkenazi Jews from origins near Lake Tiberius and Cairo. It is not entirely suprising then to find that in a work made between 1299 and 1300 in Spain, but illuminated by Joseph called ‘the Frenchman’, we find again closely similar motifs to those in MS Beinecke 408. In this case, the example on the left comes from the Cervera bible a work otherwise very different in style and layout. The comparative example is a detail from folio 28r.
As I’ve been demonstrating in these posts, many other items in the Voynich manuscript offer similar testimony to an east-west transmission of its matter between the mid-twelfth to late thirteenth century.
It was not until the fifteenth that there emerged within the Latin environment a type of plant-book collected later by Ulisse Aldrovandi, and by him classified together as ‘herbals of the alchemists‘. They have in common a set list of plants (as the linked page explains) and the use of heavy-looking icons, often but not invariably set at the level of the roots. Stylistically, they have nothing, or at best very little indeed, in common with what we find in MS Beinecke 408. I would suggest that they are a result of a fifteenth century fashion for inventing ‘hieroglphs’ which began when a Latin monk found, and appropriated from its library in a Greek monastery, a copy of Horapollo’s Hieroglyphica. It caused a fad among the elite of fifteenth century mainland Europe, Albrecht Durer being one of the artists fascinated by it.
One can understand that those intent on arguing everything about MS Beinceke 408 belongs to a Latin culture, environment, and authorship should have real difficulty coping with contrary evidence such as this within the primary source. What is less easy to sympathise with is that the means used to cope with it generally reduce to a determination to ignore that evidence, and tactics largely based on denigrating the author – as a means to discourage others from paying the evidence its due attention.
Most baffling of all are lofty assertions that the evidence never addressed, the arguments never debated, are “dismissed”.
These are techniques of advertising or political manoeuvering, and hardly help those making genuine efforts to interpret and provenance the manuscript correctly.
Against the theoretical constructs and circumstantial narratives used to support the “all Latin” idea, we have arguments from linguistic analysis, from experienced and qualified botanists, and seven years’ exposition of the imagery by the present writer. That exposition is entirely adduced from the primary source, relevant comparative imagery and reference to the historical, social and archaeological context.
It is not a case of an ‘eastern theory’ but of reasonable conclusions about the primary source – which itself announces on almost every folio its non-Latin origins and character. Even the page-layout contradicts the “all Latin” narrative/theory.
In which regard, I might mention another author’s comments about the Mashhad Dioscorides: 
which is perfectly true, and is among the reasons why I do not ascribe formulation of these botanical images to upper Mesopotamia, but rather to those regions where Indian, Persian, Yemeni and even Genoese mingled during the thirteenth century: the maritime routes which linked southeast Asia to the Persian Gulf and, via the Red Sea, to Fustat. To demonstrate the parallel presence of Indian custom in MS Beinecke 408 is not at all difficult. The first of the following examples is in what is called Warli style and the second, below, Kalamkari.
 I am not certain what is meant by ‘Hisn Kefir’ though probably Hasankeyf, known to the Greeks as Κιφας, Cephas; to the Latins as Cepha from the Syriac ܚܨܢ ܟܐܦܐ Ḥéṣn Kayfa. The northern Kurds have it as Heskîf, from the Arabic: حصن كيفا The town was a military base for Roman border guards watching the Sassanian border. It was spared during the Mongol invasion, for in 1260 Hulagu was obliged to return to central Asia after learning of the death of his brother, the great Khan.
 Mayaffariqin. Diyarbakır. Syriac: ܡܝܦܪܩܝܛ, Mayperqiṭ; Greek: Mαρτυρόπολις, Martyropolis; Armenian: Նփրկերտ, Np’rkert; Kurdish: Farqîn; Arabic: ميافارقين, Meiafarakin or Mayyafariqin;Ottoman Turkish: ميا فارقين Meyafarikîn; mod. Turkish: Silvan.
 Anna Contadini, Arab Painting: Text and Image in Illustrated Arabic Manuscripts, (2010) p.36.
 again, Contadini’s work is invaluable. See the reference cited above, and also her A World of Beasts: A Thirteenth-Century Illustrated Arabic Book on Animals .. (Brill, 2011) esp. Chapter 7.
 all botanical identifications for folios in MS Beinecke 408 by the present author.
 Nicholas Ambraseys, Earthquakes in the Mediterranean and Middle East: A Multidisciplinary Study … CUP (2009).
 I don’t discount the possibility that the original ‘Herbal of the Alchemists’ had also been brought to Europe about that time, and even that the type might descend from a late antique or Alexandrian work. For want of any similar in the Arabic or Jewish corpus, however, I must suppose the ‘herbal of the alchemist’ to have been a Latin invention. A great deal has been written on the subject of this craze for ‘hieroglyphic’ forms in Renaissance works. The text has been translated into English. George Boas, The Hieroglyphics of Horapollo, Princeton University Press. Originally published in 1950. My copy is the 1978 reprint, but I see another printing was made in 1993. Boas includes a most interesting discussion of Durer’s use of ‘hieroglyphs’ from that source.