RELATION TO ENVIRONMENT 



521 



flowers. In the freshly opened flowers the stamens are curved up- 

 ward in front of the opening of the spur, and as they successively 

 discharge their pollen they bend downward, and their place is taken 

 by the three-parted stigma, which is thus in position to be dusted 

 with pollen by any insect or bird which has previously visited a 

 younger flower, and without such visitors the pistil must remain un- 

 pollinated. Similar tubular nectaries are found in the Larkspur and 

 Columbine, which are visited by similar insects and humming-birds. 



In many tubular 

 zygomorphic flowers A 



such as the Foxglove 

 (Digitalis), Pentste- 

 mon, Gladiolus, many 

 Labiatae and Scrophu- 

 lariacese, the stamens 

 are pressed against the 

 upper arching lip of 

 the flower, while the 

 stigma hangs with 

 its stigmatic surface 

 turned away from and 

 hanging below the 

 stamens, in such a po- 

 sition as to be readily 

 pollinated by a bee on 

 its arrival with a cargo 

 of pollen taken from 

 a younger flower, but 

 usually is not mature F IO . 491. _ A, B, Salvia pratensis, illustrating pollina- 

 when the pollen of its tion. B, an older flower. (After NOLL.) C-G, 



Orchis spectabilis. C, flower with the upper part of 

 the perianth bent back to show the relative positions 

 of the lip, I, and column, gy. D, column seen from in 

 front; an, stamen ; st, stigmatic surfaces; d, disk, at 

 base of the pollinium. E-G, successive positions 

 assumed by the pollinia after being removed from 

 the anther. 



own stamens is shed; 

 and, moreover, pollen 

 falling from the sta- 

 mens lodges on the 

 back of the stigma and 



not upon its receptive 



surface. When a bee enters one of these bilabiate flowers, it clings 

 to the lower lip and creeps more or less completely into the flower, 

 thus bringing its back against the open anthers and carrying away 

 the pollen, which is transferred to the stigma of the next flower 

 it visits. 



In various species of Salvia (Fig. 491) there is a special apparatus 

 for insuring cross-fertilization. The stamens are reduced to two, 

 and in these the connective of the anther is very much developed, 

 and only one lobe of the anther produces pollen, the, other forming a 



