94 HOW ARE ANIMALS AND PLANTS DEPENDENT? 



motto. 



having pistils and stamens of three lengths. Pollen grows best 

 on pistils of the same length as the stamens from which it came. 



The stamens and pistil ripen at dif- 

 ferent times in some flowers. The 

 " Lady Washington " geranium, a 

 common house plant, shows this 

 condition. 



Pollination of the yucca. A very 

 remarkable instance of insect help is 

 found in the pollination of yucca, a 

 semitropical lily which lives in the 

 washes and semi-desert regions in 

 our Southwest. The anthers of this 

 flower reach nowhere near the stigma, 

 and the plant has to depend upon 

 insects for fertilization. The insect 

 which accomplishes this is the pro- 

 nuba (pro'nu-bd) moth. The female 

 moth gathers pollen from the anthers 

 of these blossoms and shapes it into 

 a pellet. She flies to another flower, 

 and inserts her ovipositor into the 

 ovary of the flowers and lays her eggs among the ovules. She 

 then thrusts the pollen ball into the opening which extends the 

 length of the style. When the egg hatches, the caterpillar feeds 

 on some of the young seeds which have developed along with the 

 larva. Later it bores its way out of the seed pod and escapes to 

 the ground, leaving the plant to develop the remaining seeds 

 without further molestation. 



How the fig is pollinated. The pollination of the fig is another 

 wonderful example of adaptation. The fig is not a fruit but a 

 cluster of fruits, growing inside the inturned ends of a fleshy 

 flower stalk. There may be three kinds of flowers in the clusters, 

 some bearing only stamens, some with only pistils with long 

 styles, and others, pistils with short styles. Some fig flower 

 clusters have long-styled pistillate flowers only, others contain 

 both short-styled and staminate flowers, the latter above the 



The pollination of yucca. What is the 

 moth doing in the lower figure ? 



