URTICACILE 



501 



Cotyledons rotund, emarginate, pubescent on the upper surface, 

 glabrous beneath ; lamina 4 mm. long, 4-5 mm. wide ; petiole long 

 slender, channelled above, slightly pubescent, pale green or trans- 

 parent, 4 mm. long. 



Stem herbaceous, erect, ridged and furrowed, pubescent with short 

 deflexed and bulbous-rooted, stinging hairs, pale green or stained 

 purple on the ridges ; 1st and 2nd internodes each 1-5 cm. long. 



Leaves simple, cauline, opposite, decussate, stipulate, petiolate, 



FIG. 650. Urtica dioica. A, achene, x 30. B, longitudinal section of 

 achene, x 30: Ch, chalaza ; T, testa; P, endosperm; A, pericarp. 

 C, transverse section of achene, x 30 : A, pericarp; T, testa; P, endo- 

 sperm ; C, cotyledon. 



pubescent on both surfaces, and, like the stem, more or less abun- 

 dantly furnished with bulbous-rooted stinging hairs on both sur- 

 faces, five-nerved at the base, and alternately penninerved upwards ; 

 nerves incurving, reticulate ; petioles subterete, narrowly channelled 

 above, and shallowly ridged and furrowed on the back, pubescent, 

 and usually bristly with stinging hairs ; stipules small, subulate, 

 acute, subciliate in the seedling plant, ovate-oblong, obtuse, tri- 

 nerved, ciliate, and pubescent in the adult. 



