File:The natural history of plants, their forms, growth, reproduction, and distribution; (1902) (14578991759).jpg

Identifier: naturalhistoryof02kern (find matches)
Title: The natural history of plants, their forms, growth, reproduction, and distribution;
Year: 1902 (1900s)
Authors: Kerner von Marilaun, Anton, 1831-1898 Oliver, Francis Wall, 1864- Macdonald, Mary Frances Ewart Busk, Marian Balfour, Lady
Subjects: Botany
Publisher: London, Blackie
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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in the formsof the flowers and of their insect-visitors. A brief reference to two of the moststriking modifications is all we can give here. The greatest variation is exhibited,as we said before, by the labellum and the rostellum. In some genera—in theTwayblade (Listera), for example—the part of the lip which contains the honeyis not bowl-shaped, but in the form of a long, narrow furrow, and the secretion REMOVAL OF POLLEN IN ORCHIDS. 255 is licked up by small beetles. In other instances the back of the lip is producedinto a spur lined with cells full of sweet juice, to which insects obtain access bypiercing the walls of the cells. The genus Orchis affords an example of this.Honey of a sort peculiarly attractive to butterflies is secreted in the tubular spurin other cases, such as Gynmadenia and Habenaria (see fig. 258 ^, p. 227). Two separate particles of viscid matter are often produced on the rostellum,each being in connection with one only of the pollen-masses (e.g. Habenaria
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Fig. 268.—Withdrawal and deposition of pollinia in the flowers of an Orchid Flowering spike of the Broad-leaved Helleborine (Epipactis latifolia) upon which a wasp (Vespa Austriaca) is alighting^ A flower of the same seen from the front. » Side view of the same flower with the half of the perianth towards theobserver cut away. * Thejwo pollinia joined by the sticky rostellum. 6 The same flower being visited by a wasp, whichis licking honey and at the same time detaching with its forehead the tip of the rostellum together with the pair ofpollinia. « The wasp leaving the flower with the pollinia cemented to its head; the pollinia are erect. The waspvisiting another flower and pressing its forehead with the pollinia (which in the meantime have bent down) against thestigma. 1 nat. size; the other figures x 2. chlorantha, the Large Butterfly Orchis). Insects then frequently only draw oneof the pollen-masses out of the anther, instead of both, as they leave the flower.In species of the

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