FLOWERS AND THEIR WORK. 243 



flies and Bee-flies) and the shorter-tongued bees e.g. bur- 

 rowing bees (Andrena, tongue 2 or 3 mm.), hive- bees (Apis, 

 tongue 5 or 6 mm.) and wasps. 



The concealment of the honey is effected by a further 

 deepening of the flower, due to formation of a receptacle- 

 tube, or to the sepals or petals (or both) growing out verti- 

 cally from the receptacle (instead of spreading as in shallow 

 flowers), and in many cases being joined below to a tube i.e. 

 being gamosepalous or gamopetalous. 



Examples of medium-tubed flowers are seen in Blackberry, 

 Currants, Gooseberry, Pasque Flower, Willow-herb, Geranium, 

 Mint (compare these to see how the tube is formed in each 

 case, and try to find other examples). Some flowers seem to 

 be chiefly visited by wasps, e.g. 'FigwoYt(Scrophularia}, Snow- 

 berry, Epipactis, Cotoneaster. 



Some of the most interesting flowers belong to this type and 

 the next, including the characteristic " bee-flowers," i.e. flowers 

 adapted to, and extensively visited by, bees. 



269. Long-tubed Flowers. When the flower-tube be- 

 comes longer, all these shorter-tongued insects are more or 

 less completely excluded, and the flower is adapted for, and 

 chiefly visited by, the larger bees (especially the humble- 

 bees), butterflies, and moths. Many flowers belonging to the 

 Lily, Daffodil, and Iris families of Monocotyledons come 

 under this type. In most long-tubed flowers the honey is 

 found only in the lower part of the tube, but in Crocus it 

 fills the space between the style and the long flower-tube, and 

 is therefore easily reached by bees and butterflies. 



Flowers like those of Papilionaceae, Snapdragon, and Toad- 

 flax can only be opened by large bees, and only the longest- 

 tongued bees can reach the honey in such flowers as 

 Monkshood and Larkspur. The humble-bees have longer 

 tongues (about 10 mm. in Bombus terrestris, 20 mm. in B. 

 hortorum and in Anthophora) than hive-bees. Moreover, the 

 humble- and hive-bees have the most perfect mechanism (the 

 " pollen-baskets " on the hind-legs) for collecting pollen to 

 mix with honey and feed their brood. Humble-bees are par- 

 ticularly skilful in finding the way to well -concealed honey. 



Blue, purple, and red colours are often associated with 

 flowers visited by bees (especially blue and purple) and 



