48 NATIVE BRITISH ORCHIDACE^ 



Dr R. von Wettstein {O.B.Z. p. 595 (1889)) included Cephdanthera in the genus 

 Epipactis, in which he was followed by Schulze {Orchid. Deiitschlands, PL 56). Now 

 that the method of fertilisation and the reason for the peculiar construction of 

 Cephalanthera are understood, it is clear that the flower embodies a different concep- 

 tion, and is designed on a different plan from that of Epipactis. The latter belongs to 

 a different line of evolution. Cephalanthera is a very ancient genus which shows us 

 how cross-pollination was possible in the Monandra; before a rostellum had yet been 

 evolved in the Orchidaceas. Epipactis exhibits a large and very efficient rostellum, 

 though of simple construction. 



Cephalanthera approaches the Liliaceous type of flower, and differs from the pre- 

 vailing Orchidaceous t}^e in the following points: (i) The anther is suspended from 

 the summit of a filament (stalk). (2) The poUen-grains are single, not united to form 

 tetrads. (3) There is no rostellum. 



Q^/W^»//'^ra shows a transition from the mechanism of the Diandr^ (Cypripediums) 

 to that of the Monandrse. It is akin to Cjpripedium in that it makes use of a narrow 

 gangway to compel an insect making its exit from a flower to smear itself with 

 adhesive matter by friction against a higlily viscous surface. In Cjpripedium the viscid 

 matter is secreted by the anther, and contains the pollen-grains within itseff. It can 

 be drawn out into threads. In Cephalanthera there is no viscid matter in the anther. 

 The viscous fluid secreted by the stigma is sufficiently abundant to smear the insect's 

 thorax, so that in passing the face of the anther immediately above the stigma the 

 protruding centres of the bowed-out pollinia are picked up and carried off. This 

 transfer of function from anther to stigma is noteworthy, for it is the beginning of a 

 long chain of evolution, in which the upper stigma ceases to function as such and 

 develops into a rostellum, a new organ peculiar to the Monandrae, varying from the 

 simple ball of Epipactis to the beautiful mechanism of Orchis and Ophrys. 



I. Cephalanthera grandiflora (L.) Babington 



PL 3; PL C, fig. I (p. 50). Cephalanthera pallens Rich. 

 Large White Helleborine 



Rhizome hard, short, woody. Roots many, short, stiff, corky. Stem 15-50 cm., 

 nearly round, erect, rigid, solid, often flexuous, angled, and rough above with trans- 

 lucent ridges, leafy throughout, with 2-3 loose-fitting brown membranous ribbed 

 sheaths at base, the upper sometimes green-tipped, the new bud arising at the junction 

 of rhizome and stem. Leaves few, distant, passing gradually into bracts, dull or 

 greyish green, ovate-oblong to oblong-lanceolate, obtuse or acute, often wavy-edged. 



