I don’t know how sure I am myself about this identification, but I add it because we have a nice short bit of prose to go with Bupleurum falcatum, whose root is one of the ‘treasures’ in the older Chinese work, the Shen Nong Ben Cao Jing.
I have to say that it was believed until recently, and may still be believed widely, that there was no extant copy of Shen Nong‘s Herbal. However, there has been an edition by Shouzhong Yang published by Blue Poppy Press as The Divine Farmer’s Materia Medica: A Translation of the Shen Nong Ben Cao Jing (2007).
I normally begin by analysing an image to determine the target’s habitat (water plant etc.); human context (cultivated or not..); habit (creeper, shrub..) and then look carefully at leaf and petiole because almost invariably they are shown with ‘photographic realism’. That done, I go back and check any posited identification made from those criteria against such cues or mnemonics as I can recognise in the drawing. No element in the drawing can be ignored; if any obvious conflict crops up between the evidence and my evolving identification – at any stage – it is my identification that is thrown away.
In this case, I haven’t followed that method because I found a description of uses for Radix Bupleuri which is short, old enough, and very well known so I looked for some picture in the manuscript that might possibly suit it. Great excuse and perhaps some fun at last for people interested less in history or in art analysis than in the written part of the manuscript.
Two kinds of Bupleuri are represented in the following botanical drawing and (to judge by the varied form for the leaves) perhaps also on folio 43v (Beinecke foliation). Bupleuri occur very widely, from China to the west.
Here’s the text, in translation of course.
Chai Hu (Radix Bupleuri) is bitter and balanced. It mainly treats bound qi [chi] in the heart, abdomen, intestines and stomach, drink and food accumulation and gathering, cold and heat, and evil qi [chi]. It weeds out the stale to bring forth the new. Protracted taking may make the body light, brighten the eyes, and boost the essence. Its other name is Di Xun (Earth Fuming). It grows in rivers and valleys. (op.cit., p.28)
A paper  published in the Journal of Pharmaceutical Science and Research says of it:
The genus Bupleurum [L].. of the family Apiaceae (Umbelliferae).Extracts and essential oils of Bupleurum genus plants have been largely used in traditional medicine for their anti-inflammatory and antiseptic activity. Radix Bupleuri (dried roots of B. chinense DC. or B. scorzonerifolium Willd), known as ‘Chai-Hu’, is one of the most frequently prescribed crude herbs in the prescriptions of traditional Chinese medicines for the treatment of inflammatory diseases, nephrosis syndrome and auto-immune diseases.
investigation showed that the antibacterial activity of B.rotundifolium was attributed to the essential oil of roots.
 G. Nageswara Rao, G. Ravi and S.Sharath Kumar Goud, ‘Isolation and Identification of Antibiotic Activity Containing Compounds from Bupleurum rotundifolium L’, Journal of Pharmaceutical Science and Research, Vol.4(5), 2012, pp. 1807 – 1809 online as a pdf.
another notes that:
Bupleurum root is widely used in traditional medicine for the treatment of fever, pain and inflammation associated with influenza or the common cold …
The essential oil of Bupleurum rotundifolium L. [is] grown in Konya, Turkey … 
 online)Essential oil of Bupleurum rotundifolium L. flowers’, Planta Med 2009; 75 – PJ108. (abstract,
Well – it’s a possibility.
If you want to know more about B.falcatum, you can read the monograph published by the World Health Organisation. WHO Monographs on Selected Medicinal Plants – Volume 1. (On that linked page, click on Radix Bupleuri, and more information should come up.)
An excellent site for pictures of Chinese materia medica with their roots is ‘Chinese Medicine Specimen Database’, which gives the English name for Bupleuri ~ ‘Chinese Thoroughwax root’. Another long list of photos of is the Yamasaki collection here.
Cultivation info here.
We have no absolute certainty of when the Voynich botanical section first came to Europe. All we know is that it is inscribed with Jacob Horcicky‘s name after he had been ennobled, and this occurred about 1607. The wiki biography isn’t too bad. Dr Mustard’s’ water’ probably wasn’t made from mustard; I have read (though no longer have the reference) that it is thought to have been something close to Eau de Cologne.
Many academic papers about the Angiosperm Flora of India, including Bupleurum here.
and if you like the idea of Bupleurum in general but want to compare the two I’ve suggested with others, there is a list with Arab and German names, and natural distributions in John H. Wiersema, Blanca León, World Economic Plants: A Standard Reference, Second Edition. (p.124)
Another book published in the nineteenth century is the type they just don’t make any more and it provides some classical references which imply that B. rotundifolia grew naturally around Alexandria. Perhaps it still does.
C[harles] Pickering, The Geographical Distribution of Animals and Plants, [ being] Volume XV of The United States Exploring Expedition (1838-1842), Boston: Gould and Lincoln, 1863. (p.82). Online through the Internet Archive here.
I haven’t looked out any traditional uses for B. rotundifolia, but the way the roots are drawn, I’m guessing that it contains a saponin that was gentle enough for fine (silk?) cloth or for hair, and perhaps another substance which gave it/them added body.
On the last point, there is a paper about B.kaoi, which grows only in Taiwan.
M.H. Yen, C.C. Lin, C.H. Chuang, S.Y. Liu, ‘Evaluation of root quality of Bupleurum species by TLC scanner and the liver protective effects of “xiao-chai-hu-tang” prepared using three different Bupleurum species’, J Ethnopharmacol. 1991 Sep;34(2-3):155-65. (abstract online)
In an article written by S. Karuppusamay, ‘Medicinal plants used by Paliyan tribes of Sirumalai hills of southern India, Natural Product Radiance,Vol.6(5), 2007, the author says that the Paliyan tribes use the seeds of B.mucronatum (Kattucheeragam) into a strong decoction taken orally once a day to cure chronic stomach pain. (p.438). The Sirumalai hills are in the eastern Ghats, an area of particular interest to us, and the Paliyan tribes are formally registered as one of India’s pre-Dravidian peoples.
… and England, where Georgina Trower painted Bupleurum rotundiflorum in Essex, 1905.