THE FLOWER 



217 



organization are characterized by having their organs free 

 and hypogynous, while the more highly developed forms show 

 a tendency to consolidation and union of parts, and the 

 epigynous mode of 

 insertion. Irregular- 

 ity also, since it in- 

 dicates specialization 

 and adaptation to a 

 particular purpose, 

 may be regarded as a 

 mark of advanced 

 evolution. 



243. Dissection of 

 a bilabiate flower. — 

 Make a similar study 

 of the flower of a 

 salvia, dead nettle, 

 catalpa, or other spec- 

 imen of the bilabiate 

 kind. Make diagrams 

 and report as to (1) numerical plan ; (2) presence or absence 

 of parts ; (3) regularity ; (4) union of parts ; (5) position of 

 ovary. Observe especially the relative position of stigma 



Figs. 323, 324. — Salvia: 323, a newly opened 

 flower, showing the pollen-covered anther striking 

 the back of a visiting bee ; 324, an older flower, 

 witli the protruding pistil rubbing against the back 

 of a bee covered with pollen from a younger flower. 



325 'd 



Figs. 325, 326. — Salvia : 325, longitudinal section through a flower, showing 

 the rocking connective which is struck at o by a visiting insect ; 326, section of the 

 same flower after being visited, showing the lower arm of the connective pushed 

 back and lowering the anther. 



and anthers ; is it such that the pollen can reach the stigma 

 without external aid ? Does the peculiar shape of the corolla 

 serve any other purpose than to attract the attention of 



