White and Greenish 



other clovers comes off on its sticky surface before his abdomen 

 gets freshly dusted from the anthers, which are necessarily rubbed 

 against while he sips nectar. On the removal of his pressure, the 

 floret springs back to its closed condition, to protect the precious 

 nectar and pollen from rain and pilferers. As the stigma projects 

 too far beyond the anthers to be likely to receive any of the 

 flower's own pollen, good reason is there for the blossoms guard- 

 ing their attractions for the benefit of their friends, which transfer 

 the vitalizing dust from one floret to another. By clustering its 

 small flowers in spikes, to make them conspicuous, as well as to 

 facilitate dining for its benefactors; by prolonging its season of 

 bloom, to get relief from the fiercest competition for insect trade, 

 and so to insure an abundance of vigorous cross-fertilized seed, 

 this plant reveals at a glance some of the reasons why it has been 

 able to establish itself so quickly throughout our vast area. 



Both the white and the yellow sweet clover put their leaves 

 to sleep at night in a remarkable manner: the three leaflets of 

 each leaf twist through an angle of 90, until one edge of each 

 vertical blade is uppermost. The two side leaflets, Darwin found, 

 always tend to face the north with their upper surface, one facing 

 north-northwest and the other north-northeast, while the termi- 

 nal leaflet escapes the chilling of its sensitive upper surface through 

 radiation by twisting to a vertical also, but bending to either east 

 or west, until it comes in contact with the vertical upper surface 

 of either of the side leaflets. Thus the upper surface of the ter- 

 minal and of at least one of the side leaflets is sure to be well 

 protected through the night; one is "left out in the cold." 



The dried branches of sweet clover will fill a room with 

 delightful fragrance ; but they will not drive away flies, nor pro- 

 tect woollens from the ravages of moths, as old women once 

 taught us to believe. 



The ubiquitous White or Dutch Clover (Trifolium repens), 

 whose creeping branches send up solitary round heads of white 

 or pinkish flowers on erect, leafless stems, from May to Decem- 

 ber, in fields, open waste land, and cultivated places throughout 

 our area, Europe, and Asia, devotes itself to wooing bees, since 

 these are the only insects that effect cross-fertilization regularly, 

 other visitors aiding it only occasionally. When nets are stretched 

 over these flowers to exclude insects, only one-tenth the normal 

 quantity of fertile seed is set (see page 101). Therefore, for the 

 bee's benefit, does each little floret conceal nectar in a tube so deep 

 that small pilferers cannot reach it ; but when a honey-bee, for 

 example, depresses the keel of the papilionaceous blossom, abun- 

 dant reward awaits him in consideration of his services in trans- 

 ferring pollen. After the floret which he has been the means 

 of fertilizing closes over its seed-vessel on his departure, it gradu- 

 ally withers, grows brown, and hangs downward, partly to indi- 



14 209 



