NEOTTI E^—LISTERA 97 



pronounced saprophytism of Neottia, the plants are so different in appearance that 

 they are generally regarded as forming distinct genera. No other European orchids 

 display a tongue-shaped rostellum with longitudinal cells like gun-barrels loaded with 

 extremely viscid fluid, simultaneously discharging their contents when a sensitive 

 portion of the under-surface of the rostellum is touched. 



Genus VI LISTERA R. Br. 



Column short. Anther hinged to column, persistent, sessile. Pollinia club-shaped, 

 yellow, without caudicles, bi-partite, or divided into two. Stigma on face of column 

 just below the rostellum, transversely oval or kidney-shaped. 



Small herbs with numerous rather fleshy roots and a very short rhizome. Leaves 

 two only, nearly opposite. Flowers green, or purplish red, inconspicuous. Bracts 

 shorter than the twisted stalk of the ovoid, short untwisted ovary. Sepals and petals 

 loosely connivent or spreading, exceeded by the narrow strap-shaped forked lip. Ripe 

 capsule ovoid or nearly globular. Seeds oblong, testa transparent, netted, cells not 

 striate, embryo small, without suspensor (stalk). 



Easily recognised by the single pair of apparently opposite short flat rounded leaves, 

 the small green or reddish flowers with a narrow forked lip, the stalked short nearly 

 globular ovary, and the bunch of rather fleshy roots. Platanthera is the only other 

 British genus with but two nearly opposite leaves, but the flowers are white and 

 have a long spur. About 12 species are known. 



KEY TO SPECIES 



1. Plant tall, with a single pair of large oval leaves, and a long many-flowered spike- 



like raceme of green flowers. L. ovata 



2. Plant short, frail, very slender, with two small heart-shaped leaves and a short 



loose raceme of very small dull purplish red flowers. L. cordata 



I. LiSTERA OVATA R. Br. 



PI. 17 (p. 98). Twayhlade 



Rhizome short, creeping, deeply buried. Roots many, long, sinuous, moderately 

 thick. Stem erect, tall (20-60 cm.), pale green, solitary, downy above with 1-2 small 

 green triangular bract-like leaves, glabrous, whitish and thicker below, with 2-3 

 membranous scale-like sheaths at the base. Leaves two, spreading horizontally, just 

 below the middle of the stem, almost opposite, broadly oval, sheatlaing at the base, 

 obtuse, mucronate, rather thick, glabrous, green, with five or more principal nerves. 



GEO 13 



