. The various contrivances by which orchids are fertilized by insects. Fertilization of plants; Orchids. 50 OPHEEjE. CuAr. II. presents a wonJerful contrast in every flower producing a capsule. Ophrys aranifera, or the Spider Ophrys.—I am in- debted to Mr. Oxenden for some spikes of this rare Fig. 6. species. Whilst the poUinia remain enclosed within their cells, the lower part of the cau- dicle projects up in a straight line from the viscid disc, and therefore has a very different ^ '"a^ form from the corresponding Ophiys aranifera. part of the caudicle of 0. nius- A. PoUiniiim before th
. The various contrivances by which orchids are fertilized by insects. Fertilization of plants; Orchids. 50 OPHEEjE. CuAr. II. presents a wonJerful contrast in every flower producing a capsule. Ophrys aranifera, or the Spider Ophrys.—I am in- debted to Mr. Oxenden for some spikes of this rare Fig. 6. species. Whilst the poUinia remain enclosed within their cells, the lower part of the cau- dicle projects up in a straight line from the viscid disc, and therefore has a very different ^ '"a^ form from the corresponding Ophiys aranifera. part of the caudicle of 0. nius- A. PoUiniiim before the act of dfeva; but the Upper part (A, B. PoUinfum^Xrthe act of fig- 6) is a little bent forward, depression. that is, towards the labellum. The point of attachment of the caudicle to the disc is hidden within the bases of the anther-cells, and is thus kept damp; consequently, as soon as the poUinia are exposed to the air, the usual movement of depression takes place, and they sweep through an angle of about ninety degrees. By this movement they assume, supposip^g them to be attached to an insect's head, a position exactly adapted for striking the stigmatio surface, which is situated, relatively to the potich-formed rostella, rather lower down in the flower than in the Fly Ophrys. I examined fourteen flowers of the Spider Ophrys, several of which were partly withered; and in none were both poUinia, and in three alone was one poUinium removed. Hence this species, like the !Fly Ophrys, is but little visited by insects in England. In parts of Italy it is even less visited, for Delpino states* that in Liguria hardly one flower out of 3000 sets a • • Ull. OsserT. s. Dicogamia.' &c. Parte i. 1868-60, p. 1 Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Darwin, Charles, 1809-1882. New York, D. Appleto
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1895
