These species are clearly distinguishable by a character which, though faithfully indicated by Rivinus and Jacquin, has not been fixed upon by any botanist as a specific mark. In T. officinale the radiant or dilated part of the marginal flowers consists of two neighbouring petals, each of which has one large, and one very small, lobe; in T. apulum there is only one radiant petal to each flower, whose two very large lobes are equal. I would therefore propose the following definitions of the two species in question:
T. officinale, involucellis longitudine florum, foliolis ovatis incisis crenatis, petalis radiantibus geminis inæqualitèr bilobis.
T. apulum, involucellis flore brevioribus, foliolis laciniatis; superioribus angustatis, petalis radiantibus solitariis æqualitèr bilobis.
The synonyms of the former are correctly given in both editions of Sp. Pl. as well as in Fl. Brit. 294; to which are to be added Engl. Bot. t. 2440, and the unpublished figure in Fl. Græc. t. 267. There is every reason to suppose this the original Τοξδνλιον of Dioscorides. ]f Columna had been as exact as usual, his figure would have left us in no doubt respecting the character of the petals. But as it is, enough may be discerned for our purpose; and the form of the leaves, the length of the partial involucrum, and the figure of the seed, all agree with T. officinale, not with apulum.
To the latter belong the synonyms of Rivin. Pentap. Irr. t. 2, and Jacq. Hart. Vind. v. 1. 21. t. 53; which last is quoted in MSS. by Linnæus in his own copy of Sp. PI. This is likewise T. apulum of Prodr. Fl. Græc. n. 631, from which however must be removed the reference to Columna, and consequently the synonym of Tournefort depending thereon; Jacq. Hort. v. 1. t. 53, being introduced in their stead. Bauhin's Seseli creticum minimum also, being adopted from Columna, belongs to T. officinale.
