EVOLUTION 7 



Darwin believed that the obsolete anthers A^ and A^ (Text-fig. 2) had become 

 petaloid and incorporated with the lower petal (P3) to form the lip, whence its 

 frequently 3-lobed form. He based his opinion on the spiral vessels running into 

 each petal, anther, etc., believing that those formerly running to the anthers A^ and 

 Ai had been diverted into the lip. Further experience shows that flowers of Orchis 

 morio (PI. 39, fig. B), Ophrjs arachnites, Anacamptis, etc., occur in which both the 

 upper petals P^ and P^ have developed into lips, sometimes complete with spur.' 

 All three petals thus seem capable of developing into lips without outside assistance. 

 Further, flowers occur, though very rarely, with two additional lips side by side, 

 immediately above and almost touching the true lip, which is present and unchanged. 

 From their position these superfluous lips could only have been developed through 

 the agency of the group of vessels formerly supplying the obsolete anthers A^^ and Ai. 

 It is therefore clear that not only can the true lip be developed by the vessels running 

 into the petal Ps without any aid from those of the anthers A^ and Ai, but that the 

 group of vessels belonging to each of the latter is itself capable of building up a 

 perfect lip. I have seen this phenomenon in such widely separated genera as Epipactis 

 and Ophrjs. Sometimes the true lip is absent (and there are then two lips side by 

 side), sometimes it reverts to a petal. 



Development of the rostellum 

 When the transition from pollen in the form of very fine dust to pollinia built 

 up of many thousands of pollen-grains (over 120,000 in the two pollinia of Orchis 

 morio) took place, some new method of attaching the poUinia to insects became 

 necessary, as they were too large to be carried merely entangled in their hairs. 

 In the Monandras this problem was solved by the evolution of a special organ, the 

 rostellum, secreting viscid matter which sets hard on exposure to the air and cements 

 the pollinia to visiting insects. 



In Cephalanthera there is no rostellum. Insects entering the tubular flowers smear 

 their backs (thorax) with the sticky secretion of the stigma, and by its means pick 

 up the pollinia projecting from the face of the anther. In Cattleya there is a thick 

 layer of viscid matter not distinctly separated from the stigma, whose use is to affix 

 the pollinia to insects.^ In Malaxis pahdosa a little mass or drop of viscid fluid 

 occurs on the upper edge of the stigma to which the tips of the pollinia become 

 attached. 3 In the Indian Micros tjlis rhedii there is a tongue-shaped projection formed 

 of cells which, when shghtly disturbed, resolves itself into a drop of viscid matter. 

 In Epipactis the viscid matter has become enclosed in an extremely tender skin which 

 bursts on the slightest touch, glueing the pollinia to the touching object. 



' A spike of Orchis morio s.sp. picta, found by Colonel Evans at Valescure, had one flower with 

 three lips, each with a spur (each petal developed into a perfect lip), the other 1 5 flowers being normal. 

 Darwin, Fert. Orch. ed. 2, p. 248. "^ 3 [yid. p. jj^ ^ 



