Chap. IV. 



LISTERA OVATA. 117 



it is divided by longitudinal septa into a series of 

 loculi, which contain viscid matter and have the power 

 of violently expelling it. These loculi show traces of 

 their original cellular structure. I have met with this 

 structure in no other genus except in the closely 

 allied Neottia. The anther, situated behind the ros- 

 tellum and protected by a broad expansion of the top 

 of the column, opens in the bud. When the flower is 

 fully expanded, the pollinia are left quite free, sup- 

 ported behind by the anther-cells, and lying in front 

 against the concave back of the rostellum, with their 

 upper pointed ends resting on its crest. Each pol- 

 linium is almost divided into two masses. The pollen- 

 grains are attached together in the usual manner by 

 a few elastic threads ; but the threads are weak, and 

 large masses of pollen can be broken off easily. After 

 the flower has long remained open, the pollen becomes 

 more friable. The labellum is much elongated, con- 

 tracted at its base, and bent downwards, as represented 

 in the drawing ; the upper half above the bifurcation 

 is furrowed along the middle ; and the borders of this 

 furrow secrete much nectar. 



As soon as the flower opens, if the crest of the 

 rostellum be touched ever so lightly, a large drop 

 of viscid fluid is instantaneously expelled ; and this, 

 as Dr. Hooker has shown, is formed by the coalescence 

 of two drops proceeding from two depressed spaces on 

 each side of the centre. A good proof of this fact 

 was afforded by some specimens kept in weak spirits 

 of wine, which apparently had expelled the viscid 

 matter slowly, and here two separate little spherical 

 balls of hardened matter had been formed, attached to 

 the two pollinia. The fluid is at first slightly opaque 

 and milky ; but on exposure to the air for less than 

 a second, a film forms over it, and in two or three 



