MORE MARRIAGE CUSTOMS. Ill 



and in any instance calyx and corolla may be 

 coloured 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 flower- 

 ing-rush, on the other hand, which has a larger 

 and handsomer blossom, more attractive to in- 

 sects, they are reduced to six ; but these six have 

 many seeds in each, so that a single act of fertili- 

 sation sufifices for each of them. You may re- 

 member 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 blos- 

 soms, and is therefore deservedly an immense 

 favourite in flower-gardens. All the lilies have a 

 perianth (or combined calyx and corolla) of six 

 almost similar brilliantly-coloured pieces (in which, 



