460 



HUTCHINSON'S POPULAR BOTANY 



aggregated, and it is visited regularly 

 by Bombus terrestris, as I have observed 

 at the same spot (Chiavari) in the 

 Apennines." 



Explosive forms of anemophilous 

 flowers are met with in the Nettle 

 family (Urticacese) and a few other 

 species. The Great Nettle (7. dioica. 

 fig. 516) is an excellent example. Here 

 the sexes are on different plants, and 

 the flowers are small, green, and in- 

 conspicuous. While the male flower is 

 unopened, the stamens, which are fur- 

 nished with an elastic tissue, curve in- 

 wards; but as the llower matures, they 

 gradually become dry, and, a result of 

 this dryness, spring outwards, spurt- 

 ing the pollen into the air. In this way 

 they assist the wind in disseminating 

 the fecundating dust. 



The Wall-pellitory (Parietaria ojfiei- 

 nalisi, a common weed on old walls 

 and in dry waste places, scatters its 

 pollen in a similar manner. The coiled- 

 up stamens are highly irritable, and at 

 the proper time force asunder the seg- 

 ments of the calyx which hold them 

 down and iiirt out their pollen. It is 

 a remarkable fact that, in the her- 

 maphrodite flowers of this plant, the 

 brash-shaped stigma of the pistil falls 

 off before the anthers dehisce, and thus 

 self-pollination is prevented. 



Closely related to the Nettles and 

 Wall-pellitory is the equally remarkable 

 Artillery-plant (Pilea microphylla}. 

 This is a small plant, with leaves re- 

 sembling those of Wild Thyme, and 

 minute dioecious flowers, common 

 enough in indoor ferneries. The Eng- 

 lish name refers to the copious dis- 

 charge of pollen when the stamens 



straighten themselves a phenomenon which may be artificially induced 

 by sprinkling the plant with water. The anthers empty themselves 



Photo b>i] 



FIG. 565. WOOD SAGE (Teucrium 



scorodonia). 



The pale oclireous flowers are muc'.i visited by bees. 

 The purplish stamens after shoHin- their pollen bend 

 back to allow the pistil to occupy their former position 



