BEES AND FLOWERS. 



iU 



to reach the nectar (at tu/. tig. 1) the bee (D) strikes ^vith his 

 head the short sterile arm ((/(■) ^Yhi(•ll acts as a sort of h^ver to bring 

 down the long arm with its ];x>lkMi sac (a) to cover his back with the 

 fertile dnst. Thus laden the l>nsy workman flies to another flower and, 



Fig. 1. — Flower of Salvia ojHicuuilis. (Frniii Cheshire: Bi'fs iind Bcc-kfcjiing.) 

 A. Young flower, showing an atrophied pollen sac. B. Old flower, showing the stigma. C. 

 Young, longitudinal section. D. Same visited by a bee. E. Longitudinal section, base of the 

 corolla tube, a fertile pollen sac; «<• sterile pollen sac; c connective which joins the two sacs 

 and which can oscillate in hi around the filament of stamen /,• st style; luj nectary at base of 

 ovaries; ca calyx; co corolla. 



as he enters, brnshes off some pollen on the 2:)rojecting stigma (.s/'). 

 With the exception of the Salvia coeeina, stndied by Ogle and Dar- 

 win, all the sages are thus fertilized by the bees. 



Fio. 'i. — Primula vulgaris. 



A. Flower with long style (st). B. Flower with short style (sf); s s' stiginala; a o' stamcins; 



o (>' ovaries; pg pg' grains of pollen. 



Among the primroses Ave find a much larger and more varied 

 class of plants equally adapted to cross fertilization by insects, but in 

 a different manner. As illustrated in the Pihniila ndgaris (fig. 2) 

 there are amc^ng these plants two sorts of flowers: Some (B) in which 



