CHAP. X.] 



URTICACE^. 



159 



flowers have their calyx divided into four sepals ; 

 and they have four stamens, the anthers of 

 which open with elasticity, and when they 

 spring back, the pollen, which is very abundant, 

 is discharged with such force that it may be 

 seen on a fine day in summer rising like a mist 

 or light cloud over the plants. The stamens, 

 after they have discharged their pollen, lie ex- 

 tended and curved back over the segments of 

 the calyx, as shown at a i^fig- 72. The female 

 flowers have only two segments 

 to the calyx. They have no 

 style, and the stigma, when 

 highly magnified, will be found 

 divided into numerous segments, 

 as shown at h ; the seed-vessel 

 is a nut, which has a shell and 

 kernel, the latter being the 

 seed. The leaves are simple, 

 cordate, opposite to each other, and furnished 

 with stipules. They are rough on the surface, 

 and covered with glandular hairs or stings. 

 These hairs are hollow, with a cell at the base 

 filled with a peculiarly acrid liquid, and taper- 

 ing upwards so as to form a narrow tube, ending 

 in a sharp point. When the point of the sting 

 enters the skin, the pressure compresses the cell 

 at its base, and the liquid it contains is forced 

 up the tube and injected into the wound. The 



Fig. 72.— Nsttle 

 (Urtica dioica). 



