ECOLOGY OP FLOWEES 367 



stigma stands about halfway up the tube. In the long- 

 styled flowers, I, the stigma is at the top of the tube and 

 the anthers are borne about halfway up. An insect pressing 

 its head into the throat of the corolla of II would become 

 dusted with pollen, which would be brushed off on the 

 stigma of a flower like I. On leaving a long-styled flower 

 the bee's tongue would be dusted over with pollen, some 

 of which would necessarily be rubbed off on the stigma of 

 the next short-styled flower that was visited. Cross-polli- 

 nation is insured, since all the flowers on a plant are of 

 one kind, either long-styled or short-styled, and since the 

 pollen is of two sorts, each kind sterile on the stigma of 

 any flower of similar form to that from which it came. 



Trimorphous flowers, with long, medium, and short 

 styles, are found in a species of loosestrife.^ 



438. Studies in Insect Pollination. — The student cannot gather 

 more than a very imperfect knowledge of the details of cross-polli- 

 nation in flowers -without actually -watching some of them as they 

 grow, and observing their insect visitors. If the latter are caught 

 and dropped into a wide-mouthed stoppered bottle containing a bit 

 of cotton saturated with chloroform, they will be painlessly killed, 

 and most of them may be identified by any one who is familiar with 

 our common insects. The insects may be observed and classified 

 in a general way into butterflies, moths, bees, flies, wasps, and beetles, 

 without being captured or molested. 



.Whether these out-of-door studies are made or not, several flowers 

 should be carefully examined and described as regards their arrange- 

 ments for attracting and utilizing insect -visitors (or birds). The 

 following list includes a considerable number of the most accessible 

 flowers of spring and early summer, about which it is easy to get 

 information from books. 



1 See Miss Newell's Reader in Botany, Part II, pp. 60-63. 



