L.S.- 



2 NATIVE BRITISH ORCHIDACE^ 



into two poUinia (rarely four, in some exotic genera eight), which are bodily removed 

 by insects The only other family of plants having pollinia is the Asclepiadaceas. 

 There is also, in all our genera except Cephaianthera, a wonderful mechanism for 

 affixing the pollinia to visiting insects, called the rostellum. It may be a simple baU 

 of viscid matter enclosed in a tender skin, as in Epipactis latijotia (PI. A, fig. 5), m 

 the middle of the upper edge of the stigma, or, in its highest development m Britain 

 consist of one or two pouches filled with liquid in which the viscid discs to which 

 the pollinia are attached are kept moist (PI. 2, fig. 5, the two baUs at the foot of the 



central anther). ^ 7 ■ c \ 



Text-fig. I shows the different parts of the flower in the genus Orchis of the 



Monandry which contains 52 species, 42 being European, but only 12 British. 

 Each flower springs from the axU 



of a small leaf called a bract (Br., 



Text-fig. i). What appears to be the 



stalk of the flower is really the ovary 



(0/a). Within it three narrow, longi- 

 tudinal, forked wings are thicldy 



covered with a multitude of tiny 



ovules, which after being fertilised, 



develop into seeds. These wings are 



called parietal placentas (from Lat. 



paries, a wall). Usually the ovary is 



sessile, but in some genera it is 



stalked. Wlien the flower first opens 



the lip points upwards, but the 



ovary later twists through a half- n • • u 



turn so that the lip is finally directed downwards. If the ovary has a stalk, it is the 

 stalk which does the twisting. In a few genera the ovary does not twist, and the 

 flower remains pointing upwards. 



The flower consists of three sepals, an upper (U.i-.) and two lateral or side-sepals 

 (L S ) two petals (P., P.), and a labellum or lip, a development of what was origmally 

 the third petal. These together form the perianth, or floral envelopes. The lip is often 

 spurred is usually the most conspicuous part of the flower, and frequently 3-lobed. 

 It not only attracts insects by its size and colour, but affords them a convement 

 platform on which to alight, and assures their assuming the right position to come 

 in contact with the rostellum, and thus to carry off the pollinia. In the Monandras, 

 in the centre of the flower is the column. On its summit is the only fertile anther 

 (A^ Text-fig. 2), with its two cells, which split down the front, so that the pollmium 

 in each cell^is visible. In the genus Orchis and in the Opluydeas generally, each of 



Text-fig. I. 'L.S. Lateral or side-sepals. US. Upper sepal. P., P. 

 Petals Up. LabeUum. A. Anther, with the two dark pollinia 

 showing through. Sp. Spur. Sp£.. Spur-entrance. St. Stigma. 

 Sta. StaiTiinode. R. RosteUum. Br. Bract. Ov. Ovary. 



