D. P. Fowler has pointed out an apparent acrostic in the Aeneid: the first letters of the first four lines of Vergil's description of the opening of the Gates of War (mos erat Hesperio in Latio . . . 7.601-4) spell out the word Mars. The idea that the pattern is intentional is supported by Martem at the end of 603, and by the extreme appropriateness of the acrostic to its context. Although Fowler is suitably diffident ("I await the men in white coats"), finding the name of Mars in Aeneid 7.601-04 seems to this reader rather less implausible than finding Vergil's monogram in Georgics 1.429-33, where we must read the first syllables of three lines, in reverse order and skipping a line each time, to find Pu-Ve-Ma. It is true that those lines form part of a translation of Aratus' "gamma-acrostic" sphragís in Phaenomena 783-87, where lepté is included both horizontally, as the first word of 783, and vertically, that is, acrostically, in the first letters of 783-87. This being so, the doctiores among Vergil's readers would no doubt have been on the lookout for word-games. On the other hand, it seems to me that a poet as skilled as Vergil might well have inserted three, or for that matter all nine, syllables of his name into adjacent lines, reading forwards, if he had wished to seal his work in this way. Perhaps that would have been unsubtle. Nevertheless, although I would like to believe in the Pu-Ve-Ma acrostic, I find that, whenever I am half-convinced, I cannot help thinking of Macaulay's encounter with the man who had found the Number of the Beast in Napoleon's name, assuring him that "if you write Napoleon Bonaparte in Arabic, leaving out only two letters, it will give 666".
We know that many ancient poets used poetic acrostics. In De Divinatione 2.111, Cicero tells us that Ennius was one of them: he had used an akrostikhís to spell out Q. ENNIVS FECIT in one of his works, which one unfortunately not specified. When we think of Ennius' other Hellenistic characteristics, this is not surprising, though none of these lines — more precisely, not enough of them in sequence to be detectable — is represented in the surviving fragments. Now, it may very well be a coincidence, but I think it is worth pointing out that the word Mars is spelled out by the first letters of the first four words of Ennius' most quoted line (Annales 156 Skutsch = 500 Vahlen):
Moribus Antiquis Res Stat Romana uirisque.
Ennius is not Vergil and an acronym is not an acrostic, but the similarities are nevertheless striking: not only is the word spelled out the same as in Aeneid 7.601-4, the first of the 'background' words is again a form of mos.
In deciding whether the pattern is fortuitous, the length of the acronym is important. Continuation of the message beyond four letters would prove that it was intended, though it might be disputed just how many more letters would be needed for proof. The converse is not true: the pattern may be intentional, even if it only covers one four-letter word and nothing significant follows. In that case, only additional evidence of a highly unlikely kind — Ennius' autograph with colored initials? — would tell us for certain. Unfortunately, we have only the one line to work with. If we had the next, it looks as if we would know whether the first letters of Romana uirisque begin a second word, perhaps some form of ruere or rumpere, which would help to decide the question. However, it appears from Kühner-Stegmann's list of ancient notae (1.1045, §232) that the Romans counted -que as a separate word in forming prose acronyms: examples are S.P.Q.R. and Q.F.F.Q.S. (quod felix faustumque sit). If we assume that Ennius would have felt obliged to do the same in verse, then what we have in our line is MARS RUQ, which would be virtually impossible to continue. Consequently, it is likely that the evidence will remain inconclusive. I will readily grant that the occurrence of Mars in Annales 156 may very well be entirely fortuitous. In the surviving lines of the Annales, there are six other places where the initial letters of successive words spell Latin words of three or more letters, though it is not a particularly impressive list in terms of meanings: curru (77), ars (91), anus (97), rus (343), lucus (376), and cessi or perhaps even cessi ad (411). Is the occurrence of Mars in line 156 too far beyond these in appropriateness to be fortuitous? It is impossible to be certain, and perhaps I too should await the men in white coats.
Finally, although the Latin acronym was certainly well-established in prosaic contexts, I know of no evidence for ancient poetic acronyms, and the name itself is modern. Two things can be said about this. The first is that no one seems to have looked for them. Such a search might be a harmless and conceivably even useful task for a thorough and unusually unimaginative doctoral candidate. The second point is that, although ordinary acrostics are common enough, I know of no parallel for Brown's proposed reverse intermittent syllabic acrostic in Georgics 1.429-33, and a simple acronym seems a less unlikely idea on the face of it. Of course, my second argument only applies to those who believe that Brown's acrostic is deliberate.