110 



THE STEUCTURE OF FLOWERS. 



flowers of Labiates, the anterior stamens are almost invariably 

 the larger pair. On the other hand, atrophy has affected the 

 posterior side of the staminal whorl, causing the total loss of 

 the fifth stamen, and, to some extent, a reduction in length 

 of the next pair of filaments. 



When the weight of the insect is thrt)wn npon the 

 stamens, they either hang downwards, and the insect 

 is suspended upon them, as in Epilohium angustifolium, or 

 else they become declinate and then the anterior petal, being 

 relieved, does not enlarge, either remaining of the same size 

 as the rest, or else diminishes, and may even vanish alto- 

 gether. Thus Vallota, with its perfectly i-egular perianth 

 and spreading stamens, may be compared with Amarj^lUs, 

 which has declinate stamens and a small anterior petal. 

 The terminal flower of a " thyrse " of the Horse-chestnut, like 

 the terminal flower of a "truss" of Pelargonium, is often 

 regular with spreading stamens, whereas the normal flowers 



have declinate stamens, and 

 usually only four petals, the 

 fifth or anterior one being 

 altogether suppressed. 



In some flowers the sta- 

 mens are dependent at first, 

 but their anthers rise up when 

 dehiscing, and so the fila- 

 ments become declinate in 

 the pollinating stage. This 

 is the case with Delphinium, 

 Epilobiiim angustifolium, and 



Fig. 33.-Dtctamnus (after Tieghem). ^iotammus (Fig. 33) . In this 



flower the anterior petal is 

 of much the same size as the others, but is often displaced 

 (Fig. 33), and not immediately below the stamens, — this 



