308 EXPERIMENTS WITH PLANTS 



ready for pollination, and the old flowers which have 

 been pollinated, out of the way of the insects which 

 visit the flowers. What determines the position of the 

 flower and fruit? If the plants are growing in pots,^ 

 invert thern; place some in the dark and others in 

 the light, and observe the effect on the flowers. If the 

 flowers are in a long cluster, keep the main stalk 

 from bending by attaching a small weight to the end, 

 and then observe the behavior of the individual flowers. 

 Try the effect of placing the plant in a horizontal 

 position. What parts bend! Do the flowers resume 

 their original position ? Is the result due to light, or 

 gravity, or to both? Are the movements performed 

 by the stalks alone if the flowers are removed ? 



In the Snapdragon, Pea, etc., notice that when the 

 bee alights on the lower lip, the flower, which, up to 

 that time is closed, opens as the result of its weight. 

 A smaller insect would not be able to get into the 

 flower, since its weight would not suffice to bend the 

 lower lip. This is an advantage, since it keeps out 

 small insects, and especially creeping insects, which 

 would not distribute the pollen advantageously. An- 

 other device for keeping out creeping insects is a 

 band of woolly or sticky hairs below the flower, which 

 serves the same purpose as the tar applied to the 

 trunks of trees. In other cases a mass of woolly 



ilf the plants are not in pots, the flowering branches may be carefully 

 bent downward or cut oflf and placed in water, and then inverted. 



