6 ON FLOWERS AND INSECTS. [LECT. 



shown that if insects have been in some respects 

 modified and adapted with a view to the acquirement of 

 honey and pollen, flowers, on the other hand, owe their 

 scent and honey, their form and color, to the agency 

 of insects. Thus the lines and bands by which so many 

 flowers are ornamented have reference to the position of 

 the honey ; and it may be observed that these honey- 

 guides are absent in night flowers, where they of course 

 would not show, and would therefore be useless, as 

 for instance in Lychnis vespertina or Silene nutans. 

 Night flowers, moreover, are generally pale ; for in- 

 stance, Lychnis vespertina is white, while Lychnis 

 diurna, which flowers by day, is red. 



Indeed, it may be laid down as a general rule that those 

 flowers which are not fertilised by insects, as for instance 

 those of the Beech and most other forest trees, are small 

 in size, and do not possess either color, scent, or honey. 



Before proceediDg further let me briefly mention the 

 terms used in describing the different parts of a flower. 



If we examine a common flower, such for instance 

 as a Geranium, we shall find that it consists, firstly, 

 of an outer envelope or calyx, sometimes tubular, 

 sometimes consisting of separate leaves called sepals; 

 secondly, an inner envelope or corolla, which is gener- 

 ally more or less colored, and which, like the calyx, 

 is sometimes tubular, sometimes composed of separate 

 leaves called petals; thirdly, of one or more stamens, 

 consisting of a stalk or filament, and a head or anther, 

 in which the pollen is produced ; and fourthly, a pistil, 

 which is situated in the centre of the flower, and consists 

 generally of three principal parts; one or more compart- 

 ments at the base, each containing one or more seeds ; 



