1214. If the trinity or ternary division depend upon the pinnated leaf, so must also the next number depend thereupon. 1215. The third prevalent number in the vegetable world is the quinary. The quinary division originates, when to the two pinnate leaflets two others are superadded. The pentapetalous corolla is also an _odd_ pinnate leaf in a whorl-shaped position with four pinnate leaflets. 1216. The pentapetalous is naturally higher in rank than the tripetalous, and this than the monopetalous, corolla. 1217. In the former four petals are of equal rank, but the fifth or odd petal differs from them. This difference is shown in its position, size, form, design, and colouring. The odd leaf is usually larger, of a rounded form, having more ribs and other spots or markings. 1218. It appears as if, with this second liberation of fibrous fascicles from the main bundle, the differentialization were closed. For most corollæ are only quinarily divided, or admit at least of being referred back to that number. 1219. It is readily comprehended why there are only three breaks present in the number of petals, that these are denoted by one, three, and five, and that they rarely ascend to seven, nine, and so on. For the posterior pinnate leaflets are wont also to abort or be arrested in the leaves. 1220. There can be no plant with _originally_ two corolla-lobes or petals; for the fibrous bundle does not thus divide itself; one main fasciculus is always left. The cause why the principal bundle does not divide into two equal fasciculi resides in the very nature or essence of the stalk. The idea of the stalk operates throughout the whole plant. The odd or uneven leaflet is only the last expansion of the stalk. The even leaflets are its branches. 1221. For the same reason there can be no _originally_ quaternary corolla. 1222. There can be none that is originally sexanary. 1223. But an originally septenary corolla is conceivable, if forsooth the energy of light is still in a condition to separate two bundles of fibres. How rarely this occurs is well known, and thus it still continues doubtful whether this form is not to be explained by an arrest of development. 1224. Nature can produce no originally octo-, deka-, or dodeka-petalous, &c. corolla. 1225. Corollæ with originally nine, eleven, and more numbers are not impossible. The last seem only to exist. 1226. All corollas having even numbered petals, originate through arrest of the odd leaflet. 1227. The number two originates most usually and in the simplest manner from the arrest of the number three. If it originates from the quinary quantity, two pinnate leaflets are then coarrested. 1228. The aberration is recognized either from the position of the lobes or petals that have been left remaining, or from comparison of the number in other parts, in the calyx and capsule. 1229. The quaternary corolla is a quinary without the uneven leaflet.