"He who scorns false glory shall have the real thing." - Livy (Titus Livius), The History of Rome, Book XXII.
J. Keill has written: 'Introductioad veram astronomiam' 'Introductio ad veram physicam'
Nicolaus Michaelis has written: 'Argumenta communia ad inferendum unamquamque propositionem esse veram et esse falsam'
John Keill has written: 'Introductio ad veram physicam' -- subject(s): Mechanics, Early works to 1800 'An introduction to the true astronomy..' 'Introductio ad veram physicam, seu lectiones physicae habitae in Schola Naturalis Philosophiae Academiae Oxoniensis...1700...' -- subject(s): University of Oxford 'An introduction to the true astronomy, or, Astronomical lectures read in the Astronomical School of the University of Oxford' -- subject(s): University of Oxford, University of Oxford. Astronomical School
In Latin, the word vera is (1) nominative feminine singular, (2) ablative feminine singular, or (c) nominative/accusative neuter plural of the adjective verus, meaning "true".Obviously in case (3), vera is already plural. If vera is feminine singular, its plural is verae(nominative) or veris (ablative). Veras is a valid plural form, but it's the plural of veram, the accusative feminine singular.This chart might make things clearer (then again, it may not)Singularcase : masculine / feminine / neuter nominative : verus / vera / verumaccusative : verum / veram / verumgenitive : veri / verae / veridative : vero / verae / veroablative : vero / vera / veroPluralcase : masculine / feminine / neuter nominative : veri / verae / veraaccusative : veros / veras / veragenitive : verorum / verarum / verorumdative : veris / veris / verisablative : veris / veris / verisAll this may be of academic interest only, if your question is about the use of plural forms in botanical terminology. To the best of my knowledge scientific names don't tend to adhere scrupulously to the rules of Latin grammar.