184 ECOLOGY 



5. Remove from a just-opened flower all the floral organs except the 

 pistil and make an enlarged drawing of the pistil, side view. Where 

 is pollen accumulated on it ? 



6. Which matures earlier, stigma or anthers ? 



7. Watch a bee visiting the flowers and note what happens when she 

 alights on the wings. Why are the wings and keel fastened together ? 

 Imitate the action of the bee by pressing the wings and keel down- 

 ward. Explain why cross pollination is almost sure to occur. 



8. Make a list of all the attractions which this flower has for insects. 

 What insect visitors have you observed ? 



F. Study the ripe fruit of the locust. What becomes of it in the autumn ? 

 Are the seeds likely to be destroyed by animals ? Reasons ? Part of 

 the locust seeds of each season grow within a year, but others do not 

 grow until succeeding years. Advantage of this ? 



G. Write a brief essay on the ecology of the locust, explaining all its adap- 

 tations with reference to utilizing bacterial symbionts, to light supply, to 

 browsing animals, to pollinating insects, and to reproduction by seeds. 



Lathyrus odoratus, sweet pea. 



A. Sketch the entire plant. Study the distribution of the hairs on its 

 surface. Of what use may these be ? In southern Europe, where this 

 plant is common in a wild state, snails are among the most important 

 enemies of vegetation and they rarely attack hairy plants. 



B. Examine the roots for tubercles. What kind of a climber is it ? How 

 does it climb ? Why ? 



C. Sketch several leaves with tendrils in various stages of development. 

 How does the tendril pull the plant toward any support on which it 

 fastens ? 



D. Sketch a bit of stem with a flower cluster in its natural position. 

 Make a detailed study of the flower as described under Robinia. 



E. Study the ripe fruit of the sweet pea. Are the pods likely to be eaten 

 by animals? Reasons? Can you find out how the seeds are distributed ? 

 Explain how the vetches are equipped to hold their own as dwellers in 

 thickets and in tall grass or among other large herbaceous plants. 



The family LeguminoscE is a very large and important one, divided into 

 three subfamilies — Mimosoideoe, CcBsalpinioideoB, and PapilionatcB — whose 

 characteristics are based on the structure of the flowers. The first, the Aca- 

 cia subfamily, is mostly tropical ; the second, the Cassia subfamily, contains 

 three quite familiar North American genera, — Cassia or wild senna, Cercis 

 or redbud, and Gleditsia or honey locust. Most of our familiar Legu- 

 minosoe, however, belong to the third subfamily, Papilionatoe, readily recog- 

 nizable by their papilionaceous flowers. Make out a list of those which you 

 know are useful or ornamental and give their uses. 



