3 io 



The Living Plant 



is accomplished by the provision of a blotch of color, which is 

 formed and spread in a special set of leaves developed for the pur- 

 pose, the corolla. This is the reason for the existence of color in 

 flowers; it is a notice or signal, advertising to insects the position 



of the nectar, which is the real at- 

 traction. Finally, a third requisite 

 of the method is such a construction 

 of the flowers as will make it inevi- 

 table that the insect, as it enters a 

 pollen-ripe flower in the quest for its 

 nectar, shall receive on its body a 

 supply of the pollen which it will as 

 inevitably leave on the stigma in 

 entering an ovule-ripe flower. And 

 this is the explanation of the princi- 

 pal peculiarities of shapes and sizes 

 in flowers, which, because insects are 

 most diverse in form and habits, 



Fio. 110.-A flower, enlarged, of the * themselves equally diverse in de- 

 Rape with petals and sepals re- ta ji s o f construction. Furthermore, 



moved to show the contiguity of 



the nectar glands (the ovoid struc- it is plain that the reason for the 



tures near the base) to the stamens . . , , . . ., 



and pistils. (Copied from Goebei's separation of the stamens and pistils 

 into separate flowers in the wind- 

 pollinated kinds does not hold in those that are pollinated by 

 insects; for in these, on the contrary, there are advantages, as to 

 economy of number of blossoms and also of insect visits, in hav- 

 ing both stamens and pistils associated in the same flowers. This, 

 accordingly, is the prevailing condition in showy blossoms. 



Thus it is evident that the most striking features of the flowers 

 of the higher plants, including the ones with which our very con- 

 ception of the flower is most closely associated, the colored 

 corolla, nectar, odor, and striking peculiarities of shapes, exist in 

 adaptation to cross pollination by insects. Or, the matter can be 

 stated in this way, the flower is an organ evolved in adaptation to 



