114 TRANSACTIONS OF THE 



pistil. These four stamens are not of equal length, two being 

 shorter than the other two. The reason of this is becaiise, if the 

 stamens had lain side by side, the pollen would have adhered to 

 parts of the insect's head which do not come in contact with the 

 pistil, and would therefore have been wasted. Besides, it might 

 have been deposited on the eyes of the insect so as to blind it, and 

 consequently would have deterred the bee from ever visiting the 

 flower again. This idea is strengthened by the fact that in some 

 flowers, e. g. Foxglove [Digitalis purpurea), the anthers are trans- 

 verse when immatiire, but become longitudinal as they ripen. From 

 the position of the stigma which hangs down below the anthers 

 the bee comes in contact with the former before it touches the 

 latter, and consequently fertilises the stigma with pollen from 

 another flower. 



In Salvia officinalis, Figs. 7 to 10 (from Lubbock), the anthers, 

 as they shed their pollen, shrivel up, and on the other hand, the 

 pistil increases in length, and curves downwards till it comes into 

 the position shown in the diagram (Fig. 9). The stamens here 

 are reduced to two, and of these two only one half developes 

 pollen. The barren half is widely separated from the fertile one by 

 what is termed a distractile connective (Fig. 8). This connective 

 rotates upon its axis upon the filament of the stamen, as shown at 

 Fig 10. The lower lip forms a good landing place for insects and 

 the barren parts of the anthers block up the entrance to the 

 corolla tube. Now, to explain the manner of fertilisation here, let 

 us suppose that an insect visits the flower in the male stage, it will 

 in pushing its head down the corolla tube, as at Fig. 7, come in 

 contact with the barren anther lobe, which, revolving on its axis, 

 will get pushed back into the back part of the corolla (marked x), 

 and the fertile anther will be at the same time brought down upon 

 the back of the insect, and brush its pollen on to the back of the 

 insect. Now, suppose that the insect were now to visit a flower in 

 the female stage where the pistil had elongated and curved round 

 so as to block up the entrance to the coi'oUa tube, the first thing 

 that it would come in contact with would be the elongated pistil, 

 and as its back and sides were dusted over with pollen, some of 

 that pollen would be sure to be dusted into the stigma and so the 

 plant would be fertilised. The foregoing is certainly the most 

 wonderful arrangement for the prevention of self-fertilisation that 

 is to be found in the vegetable kingdom. 



