It is not necessary, in this place, to enter into the question whether the placenta is, in all cases whatsoever, a dependence of the axis, as Payer, Schleiden, and others, have maintained, or whether it be foliar in some cases, axial in others. This question must be decided by the organogenists; teratologically, however, there can be no doubt that ovules may be formed from both foliar and axial organs, and, moreover, that, owing to the variability above referred to, both in what are called natural and in what are deemed abnormal conditions, it can rarely happen that any safe inferences as to the normal or typical placentation of any family of plants can be drawn from exceptional or monstrous formations. On the subject of placentation the following authors may be consulted: R. Brown, 'Ann. Nat. Hist.,' 1843, vol. xi, 35. Brongniart, 'Ann. Sc. Nat.,' 1834, ser. 2. i, p. 308. Alph. De Candolle, 'Neue Denkschrift der Allg. Schweizer Gesellsch.,' Band v. 1841, p. 9. Duchartre, 'Ann. Sc. Nat.,' 3rd ser., 1844, vol. ii, p. 290. Ibid., 'Elem. Bot.,' p. 574; 'Rev. Bot.,' 1846-7, p. 213. Babington, 'Gard. Chron.,' 1844, p. 557. Lindley, 'Elements,' p. 89; 'Veg. King.,' pp. 313, 497, &c. Berkeley, 'Gard. Chron.,' 1850, p. 612. Unger, 'Nov. Act. Acad. Nat. Cur.,' 1850; and in Henfrey's, 'Bot. Gazette,' 1851, p. 70. Schleiden, 'Principles,' English edit., p. 385. Payer, 'Elem. Bot.,' pp. 196, 211, 224. Baillon, 'Adansonia.' iii, p. 310. tab. iv. Cramer, 'Bildungsabweichungen,' p. 20, &c. Clos, 'Ann. Sc. Nat.,' 5th ser., iii, 313, as well as any of the general treatises on botany. Reference may also be made to the chapters on Prolification and Substitutions (in the case of the carpels and ovules), and to the authorities therein cited. FOOTNOTES: [90] 'Tijdschr. voor. nat. Gesch.,' viii, 1841. tab. ii, p. 178. [91] Communication to the Internat. Bot. Congress, Paris, 1867. [92] 'Bot. Zeit.,' 1859, p. 117, tab. v. [93] 'Ann. Sc. Nat.,' ser. 2, vol. iv, 1835, p. 143. tab. v. [94] See Kirschleger, 'Flora.' 1844. p. 566 (_Scabiosa_). [95] 'Bull. Acad. Belg.,' t. xvii. part ii, p. 387. [96] 'Clos. Mem. Acad. Toulouse,' 5th ser., t. vi. pp. 51, 70. [97] 'Bull. Acad. Roy. Belg.,' xviii. part ii, p. 505, and vol. xvii, part i, p. 196, and vol. xix. part i. p. 260. [98] See also Schlechtendal, 'Bot. Zeit.,' iv, p. 804. _Primula veris, partibus perigonii spirae in modum confluentibus._ [99] Seemann's 'Journal of Botany,' vol. v, 1867, p. 158. [100] 'Journ. Linn. Soc.,' i, 1857, p. 161. _c. xylog._ [101] 'Adansonia,' ii, 306. [102] 'Adansonia,' iv, p. 70, t. i. [103] Henfrey's 'Bot. Gazette,' i, 265. CHAPTER II. PROLIFICATION.