170 



ECOLOGY 



III. Is the flower 

 characterized by 



6, odor ? 



7, color (not green) ? 



8, nectar ? 



9, sticky pollen ? 



10, opening during only part of the day ? 



11, bilateral symmetry ? 



12, facilities for insect visitors ? (See Principles, 

 Figs. 324, 325.)! 



13, mechanism for holding visitors imprisoned until 

 covered with pollen ? 



14, mechanism for pollinating visitors ? (See Prirtr- 

 ciples, Figs. 381, 332.) i 



15, two or three lengths of stamens and pistils 

 (dimorphism or trimorphism) ? 



16, unequal maturing of stamens and pistil (dichog- 

 amy) ? 



If -any of these characteristics (III) are found, the flower is pollinated by 

 insects, birds, or other animals. 



Malie a list of all the attractions displayed by the flower examined, and 

 if possible find out what visitors it receives and how their visits are utilized. 



17, a sticky stem or flower stalk ? 



18, water reservoirs along the stem ? 



19, a slippery flower stalk ? 



20, a sticky-hairy or slippery nodding calyx ? 



21, a corolla with closed throat ? 



22, stamens or pistils covering the nectaries ? 



23, a long calyx or corolla tube ? 



24, long spurs, with the nectar stored at the bottom ? 

 Make a list of these protections, and if possible study their operation. 



The following list includes a considerable number of the most accessible 

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

 tion from books. 



Is the flower under 

 examination pro- 

 tected from unde- 

 sirable visitors by 

 means of 



List of Insect-Pollinated Flowers ^ 



1. Flax Linum usitatissimum Knuth 



2. Missouri currant . . . Bibes aureum Knuth 



1 For very many other devices for pollination see Knuth-Davia, 62, and 

 Kemer-OIiver, 2. 



^ The plants in this list are arranged somewhat in the order of the complexity 

 of their adaptations for insect pollination, the simplest first. It would be well for 



