In an article in Speculum (Vol. XIX, 1944) "Botanical Observations On The Voynich MS." by Hugh O'Neill, he states the following concerning the Sunflower plant:
"The most startling identification, however, was fol. 93, which is quite plainly the common sunflower, Helianthus annuus L. Six botanists have agreed with me on this determination."
Included in the article is a copy of the referenced folio (f93r) which I had also suggested might be the sunflower, though I subsequently was more in favor of Protea as a possible match. I now wonder who first suggested that the plant drawing in f33v is Helianthus annuus?
Speculum, A Journal Of Medieval Studies, Volume XIX
(Published Quarterly by The Medieval Academy of America
Cambridge, Massachusetts, 1944, p.126.)