Laudator Temporis Acti

The setting of Horace, Satire 1.8, is the Esquiline in Rome, which used to be a cemetery, but now was the site of beautiful gardens. Witches still frequented the Esquiline under cover of darkness, to excavate bones for use in their magical rites. A wooden statue of the god Priapus tells how he scared the witches Sagana and Canidia away (lines 40-50, tr. H. Ruston Fairclough):

Why tell each detail—how in converse with Sagana the shades made echoes sad and shrill, how the two stealthily buried in the ground a wolf's beard and the tooth of a spotted snake, how the fire blazed higher from the image of wax, and how as a witness I shuddered at the words and deeds of the two Furies—though not unavenged? For as loud as the noise of a bursting bladder was the crack when my fig-wood buttock split. Away they ran into town. Then amid great laughter and mirth you might see Canidia's teeth and Sagana's high wig come tumbling down, and from their arms the herbs and enchanted love-knots.

singula quid memorem, quo pacto alterna loquentes
umbrae cum Sagana resonarint triste et acutum
utque lupi barbam variae cum dente colubrae
abdiderint furtim terris et imagine cerea
largior arserit ignis et ut non testis inultus
horruerim voces furiarum et facta duarum?
nam, displosa sonat quantum vesica, pepedi
diffissa nate ficus; at illae currere in urbem.
Canidiae dentis, altum Saganae caliendrum
excidere atque herbas atque incantata lacertis
vincula cum magno risuque iocoque videres.

Priapus broke wind, as the Latin (pepedi) makes clear.

It is a curious fact that methane gas (a chemical component of flatus) is produced in certain trees, and that the pressure of the methane gas can cause the wood to split. I learned this fact from Oliver Rackham, The History of the Countryside (London: J.M. Dent, 1986; rpt. London: Phoenix, 2000), p. 240:

Elms are subject to many diseases. They have the famous and mysterious property of unexpectedly dropping big boughs. Of this I have many times been a near-witness, with English and East Anglian elms and also in America. It happens, not under the stress of gales or heavy rain, but on calm hot days. The boughs do not, therefore, drop through weakness, but are actively severed. I suspect some connection with the bacterial wetwood that infects nearly all elms (Rackham 1975); the wetwood bacteria generate methane gas under pressure which is capable of rending the wood apart.

"Rackham 1975" is a reference to Oliver Rackham, Hayley Wood: Its History and Ecology (Cambridge: Cambridgeshire and Naturalists' Trust, 1975), which I have not seen.

There is a discussion of the phenomenon in J.C. Ward and W.Y. Pong, "Wetwood in Trees: A Timber Resource Problem," United States Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station, General Technical Report PNW-112 (August 1980), p. 12:

During the summer growing season, high positive gas pressures have been recorded in wetwood of standing hardwood trees, and these pressures are attributed to bacterial metabolism (33, 79, 191, 221, 222). Trunk gases contributing to the positive pressures in wetwood are carbon dioxide, hydrogen, methane, nitrogen, and hydrogen sulfide. Zeikus and Ward (222) established that the methane gas is produced by an autotropic anaerobe which is a secondary invader and not common to all wetwood populations even within the same host species. This methanogen, subsequently characterized and named Methanobacterium arbophilicum by Zeikus and Henning (221), is also found in soil and water.

The articles by Zeikus are cited on p. 56:

221. Zeikus, J. G., and D. L. Henning. 1975. Methanobacterium arbophilicum sp. nov. An obligate anaerobe isolated from wetwood of living trees. Antonie van Leeuwenhoek J. Microbial. and Serol. 41(4):543-552.

222. Zeikus, J. G., and J. C. Ward. 1974. Methane formation in living trees: A microbial origin. Science 184(4142):1181-1183.

Wetwood also has an unpleasant odor or pong (Ward & Pong, p. 10).

Unfortunately, I can't find any references to wetwood in fig trees.

Articles (which I haven't yet seen) on Horace, Satire 1.8, include:

• Lowell Edmunds, "Horace's Priapus: A Life on the Esquiline (Sat. 1.8), Classical Quarterly 59 (2009) 125-131
  
• Martha Habash, "Priapus: Horace in Disguise?", Classical Journal 94.3 (Feb.-Mar. 1999) 285-297