120 THE STORY OF THE PLANTS. 



alike so as almost to resemble a single row or 

 perianth. 



There is one more point about the flowering- 

 rush to which I would like to allude before going 

 on to the other threefold flowers, and that is 

 this. In arrowhead and water-plantain the 

 carpels are very numerous, but each one-seeded. 

 In flowering-rush, on the other hand, which has 

 a larger and handsomer blossom, more attractive 

 to insects, they are reduced to six ; but these 

 six have many seeds in each, so that a single 

 act of fertilisation suffices for each of them. 

 You may remember that among the fivefold 

 flowers we found a precisely similar advance on 

 the part of the marsh-marigold above the 

 bulbous and meadow buttercups. This sort of 

 advance is common in nature. Where a flower 

 learns how to produce many seeds in a carpel, 

 it can soon dispense with several of its carpels, 

 because a few now do well what the many did 

 badly. Furthermore, in higher plants, there is 

 a tendency for these carpels to unite so as to 

 form what we call a compound ovary, with a 

 single style, when one act of fertilisation suffices 

 for all of them. Such combinations or labour- 

 saving arrangements obviously benefit both the 

 insect and the plant, and have therefore been 

 doubly favoured by natural selection. 



We see this advance beautifully illustrated in 

 the largest and loveliest family of the threefold 

 flowers, the lily group, which contains a great 

 number of the handsomest insect - fertilised 

 blossoms, and is therefore deservedly an im- 

 mense favourite in flower-gardens. All the lilies 



