REPRODUCTION BY SEED 173 



the flower stalks — e.g., Silene, Lychnis — or by obstructing 

 hairs on the calyx or at the entrance of the flower. The 

 extra-floral nectaries which occur on some plants — 

 plum, cherry-laurel — may serve the purpose of diverting 

 these marauders. 



3. Flowers with fully-eoncealed honey. 



(a) Honey concealed in short flowers — e.g., geranium, 

 willow-herb, bramble, veronica, mint, ling, etc. This group 

 excludes the short-tongued insects entirely, the flowers 

 being pollinated by long-tongued flies and medium- 

 tongued bees, butterflies, and moths. These insects are 

 larger and much more sldlful in extracting honey than 

 the smaller short-tongued insects, and they usually conflne 

 their attention to one species of flower as long as possible. 

 In this way there is less waste of pollen and a greater 

 certainty of pollination. 



(6) Flowers in which the honey is concealed at the 

 bottom of long tubular coroUas, or spurs. These are the 

 most specialized of entomophilous flowers, and are only 

 visited by the longest-tongued insects — ^bees, butterflies, 

 and moths. Many of the largest and most irregular 

 flowers are visited by the humble-bee — a strong, heavy 

 insect with a long tongue. This bee has the vicious habit 

 of boring through the base of the corolla and iUegitimately 

 removing the honey without pollinating the flowers — e.g., 

 beU-heather, dead-nettle, toadflax, foxglove, Canterbury 

 beU, columbine. Through the holes thus made smaller 

 insects can enter and complete the plunder. To this class 

 belong the larger Leguminosae, Scrophulariacsee, and 

 Labiatse, many orchids, and those flowers pollinated 

 exclusively by butterflies and moths — e.g., evening-prim- 

 rose, Lychnis, species of Silene, tobacco-plant, honey- 

 suckle, primroses, etc. 



The Pollinating Insects. 



1. Bees (Hymenoptera).^ — -Bees are either short-tongued 

 (ground - bees), medium-tongued (hive - bees), or long- 

 tongued (humble-bees). They collect both honey and 

 pollen. The poUen is usually rolled up and carried away 

 in little packets on the hind-legs. Bees are the most 

 important of aU pollinators, not only because of the 

 length of their tongues, but also because of their strength, 



