A Grammatical Dictionary of Botanical Latin

fallax,-acis (adj.B): deceptive, deceitful, fallacious, compar. fallacior,-ius (adj.B); superl. fallacissimus,-a,-um (adj.A); cf. decipiens; in epithets often indicates the species has a deceptive appearance or misleading taxonomic relationship with another species: Spathantheum fallax has a deceptive similarity to S. orbigynanum; see false; see fraudulent.

- with genitive: homines amicitiae fallaces, men deceitful of friendship floribus formae fallacibus, with flowers deceptive in form.

- with dative: characteribus similitudini fallacibus, with characters deceptive in similarity.

- (mosses) Praeterea stirpes masculae a foeminis solo adspectu vix distinguuntur, et capsularùm absentia, sexus indicium summopere fallax et incertum est, cum saepe fiat aut tempestatis inclementiae aut foli vitio, aut alias ob causas, ut foeminae non foecundentur aut foecundatarum fructus adhuc tenellus pereat (Bridel), especially the male plants from the female are scarcely distinguished by aspect alone, also with the absence of capsules, the indication of the sexes is exceedingly deceptive and uncertain, while often it may be due to either inclement weather or injury of the leaf, or other causes, so that the female plant may be unfertilized or the tender plant of the first time fertilized fruits may perish.

(moss) Barbula fallax, (tricky, deceitful, a species with little distinct character and that is variable, which closely resembles other species.

Quercus x fallax (deceitful, due to its variability).

Antennaria fallax, ‘deceitful;’ Betula lutea fo. fallax, due to the normally yellowish-gray bark aberrantly brown.