OPHRYDE^— GYM NAD ENIINjE— PLAT ANTUERA i^j 



the hand, numbers of polHnia are removed by the viscid discs touching the sepals 

 of their neighbours. The reason the pollinia are affixed to the eye or proboscis in 

 Lepidoptera is that the discs do not adhere well to a very hairy or scaly surface 

 (scales being so easily detached), but in Hymenoptera the naked forehead or proboscis 

 aflFords a good hold.' On withdrawal the pollinia are more or less vertical. A few 

 seconds later, one side of the drum contracts, causing the pollinia to move inwards 

 (i.e. towards each other, if both have been withdrawn together). At the same time 

 the drum rotates through nearly a quarter of a circle, causing the pollinia to move 

 downwards till they finally point forwards, and are thus in the right position to come 

 in contact with the stigma of the next flower visited.^ 



2. Platanthera BIFOLIA Rchb. p. 

 PI. 25 B. Lesser Butterfly Orchid 



Tubers two, ovoid, abruptly tapering into an obtuse tail; roots few, short. Stem 

 20-30 cm., erect, slender, angled above, solid (towards the end of summer often 

 hollow), with 2-3 brown or wliitish tapering membranous ribbed sheaths at base. 

 Leaves two at base, about 7-13 cm. long by 2-3 cm. broad, oblong or oblong- 

 lanceolate, obtuse or moderately acute, keeled, glabrous, glossy, bright or grey- 

 green, sometimes wavy-edged, with numerous nerves with transparent parallel dashes 

 between them, tapering below to a flat wliitish winged stalk pressed against the stem ; 

 upper leaves small, bract-like, erect, shghtly decurrent, linear-lanceolate with 3-5 

 obscure nerves. Spike narrow, cylindrical, 7-1 5 -flowered, but sometimes up to 9 cm. 

 long, usually lax. Flowers white, smaller than in P. chlorantha, very sweet-scented 

 by day and especially at night. Bracts lanceolate to ovate-lanceolate, obtuse, some- 

 what keeled, slightly decurrent, about as long as the ovary (or longer) with 3-5 

 scarcely visible nerves. Ovary linear, twisted, shorter than in P. chlorantha (making 

 the spike narrower), curved (sometimes like an S), tapering. Sepals, the lateral 

 spreading, lanceolate, rather narrow, obtuse, white (crystalline under the lens), the 

 upper erect, heart-shaped, slightly stalked, obtuse, broader and shghtly shorter than 

 the lateral. Petals white or greenish white, linear-lanceolate, somewhat sickle- 

 shaped, much narrower and slightly shorter than the sepals, erect, more or less arched 

 over the column, about twice as long as the latter. Lip linear-oblong, strap-shaped, 

 obtuse, entire, longer than the sepals, directed obhquely downwards, white with 

 greenish tip. Spur long (i|-2j cm.), very slender, acute, sometimes slightly club- 

 shaped at apex, usually horizontal, greenish at least at the tip, which is filled with 

 nectar. Column small, 3 mm. tall; basal part whitish, curving round on each side 

 ' Darwin, Fert. Orch. ed. 2, p. 72. 2 Ihid. p. 71. 



GBO jjj 



