DISCS OF BLOSSOM 121 



the value of combination. So minute a flower as a single 

 calyx of hemlock or elder would have little chance of thriving 

 in the fierce competition of the copse and hedgerow in early 

 summer. In the first place it would tend to be over- 

 shadowed, and deprived of essential light and air ; and it 

 would also probably fail to attract the mating insects, unless 

 it had a disproportionately and almost impossibly powerful 

 scent. It is noticeable that the disc-flowers have not on the 

 whole a very strong scent. None of the hemlocks and 

 other umbellifers have blossoms with a scent worth mention, 

 and even the scent of the elder is not comparable, mass for 

 mass, with that of the honeysuckle or the butterfly orchid, or 

 many other flowers in bloom at the same time. The small 

 and scentless blossoms consequently form a league or con- 

 federation, and under a united constitution they do more than 

 hold their own. The umbellifers are one of the master races 

 of plants from the time of the blossoming of the cow-parsley 

 round the hedges in the hay-fields to the end of active growth. 

 Such scent as they possess is made more powerful by concen- 

 tration, but they depend more regularly upon the appeal of 

 colour. Almost all the disc-flowers are whitish, though not 

 pure white ; and there is often more body in a cream-coloured 

 mass of blossom than a pure white one when the dusk has 

 fallen. The fennel has blossoms of greenish yellow, and it 

 is noticeable that it is much more frequented by butterflies 

 than any other plants with this form of blossom. It makes 

 its appeal by day, with a richer colour that is effective by 

 daylight; but cow-parsnip and elder and the other disc-flowers 

 are not attractive to butterflies. Some of them are sought 

 out by day-flying beetles, but they are chiefly sought out by 

 the small flies which swarm in the soft dusk. The composite 

 blossom forms an effective signal-lamp, when each single 

 blossom of which it is composed would be powerless. 



