1 32 On Flowers and Insects, 



with it. Lastly, in the Small-flowered Geranium, 

 which is least of all, the stigma ripens even before 

 the stamens. Thus, then, we have a series more or 

 less dependent on insects, from the Meadow Gera- 

 nium to which they are necessary, to the Small- 

 flowered Geranium which is quite independent of 

 them ; whilst the size of the corolla increases with 

 the dependence on insects. 



In those species in which self-fertilisation is pre- 

 vented by the circumstance that the stamens and 

 pistil do not come to maturity at the same time, 

 the stamens generally ripen first. 



4. The advantage of this is probably connected 

 with the visits of bees. In those flowers which 

 grow in bunches the lower ones generally open 

 first. Consequently in any given spike the flowers 

 are at first all staminate ; subsequently the lower 

 ones, being the older, have arrived at the pistillate 

 stage, while the upper ones are still staminate. 

 Now it is the habit of bees to begin with the lower 

 flowers of a spike and work upwards. A bee, there- 

 fore, which has already dusted herself with pollen 

 from another flower, first comes in contact with 

 the pistillate flowers, and dusts them with pollen, 

 after which she receives a fresh supply from the 

 upper staminate flowers, with which she flies to 

 another plant. 



5. There are, however, some few species in 

 which the pistil ripens before the stamens. One 

 is our common Figwort. Now, why is this ? 



