_Dipterocarpus_, where
the enlarged calycine segment has a strictly vaginal arrangement of its
veins, very different from that which occurs in the true leaf-blades.
These are cases, therefore, where the sheath of the leaf is unusually
enlarged, and are not to be referred, as is often done, to metamorphosis
of one or more sepals to perfect leaves. Prolified roses, cherries, &c.,
furnish frequently parallel cases. With reference to _Mussaenda_, C.
Morren held the view that the petal-like sepal was really a bract
adherent to the calyx, and incorporating with itself one of the calycine
lobes--"soudee au calice et ayant devoree, en englobant dans sa propre
masse, un lobe calicinal." The Belgian _savant_ considers this somewhat
improbable explanation as supported by a case wherein there were five
calyx lobes of uniform size, and a detached feather-veined leaf
proceeding from the side of the ovary lower down ('Bull. Acad. Belg.,'
xvii, p. 17, _Fuchsia_, p. 169).

[258] In this order _Agrostemma Githago_ offers an illustration of a
normally leafy calyx.

[259] 'Bull. Bot.,' i, p. 6.

[260] Wolff's original opinion was that the stamens were equivalent to
so many buds placed in the axil of the petals or sepals (see 'Theoria
Generationis,' 1759, Sec. 114)--an opinion which more recently has received
the support of Agardh and Endlicher. Wolff himself, however, seems to
have abandoned his original notion, for in his memoir, "De formatione
intestinorum praecipue tum et de amnio spurio aliisque partibus embryonis
gallinacei, nondum visis," &c., in 'Comm. Acad. Petrop.,' xii, p. 403,
anno 1766, he considers the stamens as essentially leaves. See also
Linn. 'Prolepsis,' Sec. viii; Goethe, 'Metam.,' Sec. 46.

[261] Mueller (Argov.), in 'Mem. Soc. Phys. et d'Hist. Nat. Genev.,' t.
xvii.

[262] "If we keep in view the observations which have now been made, we
shall not fail to recognise the leaf in all seed-vessels,
notwithstanding their manifold forms, their variable structure, and
different combinations."--(Goethe, 'Metam.,' Sec. 78.) Wolff, 'N. Comm.
Acad. Petrop.,' 1766, xii, p. 403, expresses precisely the same opinion
as to the nature of the seed-vessel.

[263] 'El. Terat. Veg.,' p. 205.

[264] 'Ann. Sc. Nat.,' 4th series, vol. ix, p. 209.

[265] 'Adansonia,' iv, p. 70. A similar deviation has been observed by
M. van Tieghem in the ovary of _Tropaeolum majus_, 'Bull. Soc. Bot. Fr.,'
1865, p. 411.

[266] Planchon et Mares,