White and Greenisli 



what happens in the older flowers, but begin our observations, 

 with the help of a powerful lens, when the bee has alighted on 

 the spreading lip of a newly opened blossom toward the top of 

 the spire. As nectar is already secreted for her in its receptacle, she 

 thrusts her tongue through the channel provided to guide it aright, 

 and by the slight contact with the furrowed rostellum, it splits, 

 and releases a boat-shaped disk standing vertically on its stern in 

 the passage. Within the boat is an extremely sticky cement that 

 hardens almost instantly on exposure to the air. The splitting of 

 the rostellum, curiously enough, never Iiappens without insect 

 aid ; but if a bristle or needle be passed over it ever so lightly, a 

 stream of sticky, milky fluid exudes, hardens, and the boat- 

 shaped disk, with pollen masses attached, may be withdrawn on 

 the bristle just as the bee removes them with her tongue. Each 

 pollinium consists of two leaves of pollen united for about half 

 their length in the middle with elastic threads. As the pollinia 

 are attached parallel to the disk, they stick parallel on the bee's 

 tongue, yet she may fold up her proboscis under her head, if she 

 choose, without inconvenience from the pollen masses, or with- 

 out danger of loosening them. Now, having finished sucking the 

 newly opened flowers at the top of the spike, away she flies to 

 an older flower at the bottom of another one. Here a marvel- 

 lous thing has happened. The passage which, when the flower 

 first expanded, scarcely permitted a bristle to pass, has now wid- 

 ened through the automatic downward movement of the column 

 in order to expose the stigmatic surfaces to contact with the pol- 

 len masses brought by the bee. Without the bee's help this 

 orchid, with a host of other flowers, must disappear from the face 

 of the earth. So very many species which have lost the power 

 to fertilize themselves now depend absolutely on these little 



Eollen carriers, it is safe to say that, should the bees perish, one 

 alf our flora would be exterminated with them. On the slight 

 downward movement of the column in the ladies' tresses, then, 

 as well as on the bee's ministrations, the fertilization of the flower 

 absolutely depends. ' ' If the stigma of the lowest flower has 

 already been fully fertilized," says Darwin, "little or no pollen 

 will be left on its dried surface ; but on the next succeeding flower, 

 of which the stigma is adhesive, large sheets of pollen will be 

 left. Then as soon as the bee arrives near the summit of the 

 spike she will withdraw fresh pollinia, will fly to the lower flowers 

 on another plant, and fertilize them ; and thus, as she goes her 

 rounds and adds to her store of honey, she continually fertilizes 

 fresh flowers and perpetuates the race of autumnal spiranthes, 

 which will yield honey to future generations of bees." 



The Slender Ladies' Tresses (G. gracilis), with a range and 

 season of blossom similar to the preceding species, and with even 

 smaller white, fragrant flowers, growing on one side of a twisted 



167 



