THE FLOWER AND THE BEE 



different flowers and flower-clusters either on the same tree or 

 on different trees. The fertile flowers are also higher up on 

 the branch than the sterile. Even in the elm a part of the 

 flowers are unisexual. The stigmas are in a receptive condi- 

 tion two or three, or even four or five, days before the anthers 

 open, or sometimes the anthers may mature before the stigmas. 

 The pistillate flowers, whether solitary or in clusters, are nearly 

 rigid and motionless, since it would be of no benefit, if not an 

 actual disadvantage, for them to oscillate in the breeze; but 

 there is always provision for shaking the anthers. This in 

 most instances is very effectively accomplished by the pendu- 

 lous catkin; but in the beech the drooping head of staminate 

 flowers on a long stem sways easily to and fro in the wind, 

 while in the elm the stamens double in length after the flower- 

 buds expand, so that a slight air current causes the anthers to 

 vibrate. Finally they all produce a copious supply of pollen, 

 which must be protected from too much moisture. The an- 

 thers, therefore, open only when the air is warm and dry, and 

 in the event of a sudden shower the fissure may close in a few 

 seconds. An ideal condition is a clear day and a gentle breeze, 

 which prevents the pollen from falling too quickly to the ground 

 and widely diffuses it through the atmosphere, permitting it to 

 settle slowly over an extensive area. In a complete calm the 

 grains do not fall out readily from the anther-cells; but a high 

 wind whirls them away too forcibly in one direction and causes 

 excessive waste. 



Our northern hardwood forests often consist almost w^holly 

 of birches, oaks, beeches, and the other trees enumerated, 

 which cover large areas of land. There are literally acres of 

 bloom and a numberless host of flowers. For the most part 

 they are a delicate pale green, not easily distinguished from the 

 newly expanding leaves; but the catkins of the yellow birch 



