Handbook of practical botany : for the botanical laboratory and private student / by E. Strasburger ; edited from the German by W. Hillhouse ; revised by the author, and with many additional notes by author and editor.

  • Strasburger, Eduard, 1844-1912.
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Handbook of practical botany : for the botanical laboratory and private student / by E. Strasburger ; edited from the German by W. Hillhouse ; revised by the author, and with many additional notes by author and editor. Source: Wellcome Collection.

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    have here a free-central placenta. The wall of the ovary is in no way connected with this placenta. We can be quite convinced of this by cross-sections in which the wall of the ovary appears as a free ring around the central placenta, or, if an equatorial incision is made round the ovary, the style and upper part of the ovary can be lifted off like a cap from the mass of ovules, and the prolongation of this central swelling will be withdrawn from the pollen-canal. , Wanting also in the ring are the points of se- paration which enable us to determine the number of carpellary leaves concerned in forming the ovary; these however are assumed to be five, from the point of view of the numerical symmetry of the other floral parts, and from the circumstance that in many Primu- lacete the fruit-capsule dehisces at its apex with five teeth. In Frimula itself the number of the teeth with which the capsule opens is undetermined.—Instead of Primula, species of Lijsimachia [Loose-strife, Creeping Jenny, Money-wort, etc.,] or of Anagallis [Scarlet Pimpernel, Bog Pimpernel, etc.,] can be used with the same results; they all bear their ovules on a free central placenta. Let us examine now an inferior [adherent or adnate] ovary, selecting first that of Ppipactis palustris, or of some other orchid. The brown ovary lies below the point of insertion of the other floral parts. We select for cutting a young rudimentary fruit, upon which the petals have already begun to go brown. Cross- sections are very instructive, and show us a unilocular ovary, which bears equidistantly upon its wall three pairs of placentce. The placentae repeatedly divide at their inner edges, and bear a great number of ovules. The wall of the ovary has on its outer side six projecting ribs, of which three correspond to the places of insertion of the placentae; three specially strong ones alternate with these places of insertion. Each rib is traversed by a fibro-vasal bundle, or a complex of fibro-vasal bundles, besides which a small bundle lies at each place of separation of two placent88. In a superior ovary, the cross-section of which should agree completely with that here described, we should in no way scruple to consider the ovary as composed of three carpellary leaves, and to look upon the pairs of placentas as arising from the conjoined edges of two adjoining carpellary leaves. The three ribs which alternate with the lines of insertion of the placentae, we should take for the midribs of the three carpellary leaves. As we have here, however, an inferior fruit, the matter is not so simple. We can either conceive that the inferior ovary consists