2 ON FLOWERS AND INSECTS. [LECT. 



which is a small projecting lobe (Fig. 3, m). The upper 

 portion of the corolla is an arched hood (Fig. 3, co), 

 under which lie four anthers (a a), in pairs, while 

 between them, and projecting somewhat downwards, 

 is the pointed pistil (st). At the lower part, the tube 

 contains honey, and above the honey is a row of hairs 

 almost closing the tube. Now, why has the flower this 

 peculiar form ? What regulates the length of the tube ? 

 What is the use of this arch ? What lessons do these 

 lobes teach us ? What advantage's the honey to the 

 flower ? Of what use is the fringe of hairs ? Why does 

 the stigma project beyond the anthers ? Why is the 

 corolla white, while the rest of the plant is green ? 



Similar questions may of course be asked with refer- 

 ence to other flowers. Let us now see whether we can 

 throw any light upon them. 



At the close of the last century, Conrad Sprengel pub- 

 lished a valuable work on flowers, in which he pointed 

 out that the forms and colours, the scent, honey, and 

 general structure of flowers, have reference to the visits 

 of insects, which are of importance in transferring the 

 pollen from the stamens to the pistil. This admirable 

 work, however, did not attract the attention it deserved, 

 and remained almost unknown until Mr. Darwin devoted 

 himself to the subject. Our illustrious countryman was 

 the first clearly to perceive that the essential service 

 which insects perform to flowers, consists not only in 

 transferring the pollen from the stamens to the pistil, 

 but in transferring it from the stamens of one flower 

 to the pistil of another. Sprengel had indeed observed 

 in more than one instance that this was the case, but he 

 did not altogether appreciate the importance of the fact. 



