ECOLOGY OF FLOWERS 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. 
