158 BRITISH FLOWERING PLANTS chap. 



curious M. scutellata of North Africa ; others are 

 covered with hooks, and carried by animals. 



M. sativa (Lucerne). — Much cultivated, but not in- 

 digenous. It is a native of the Eastern Mediterranean 

 region. It produces honey, and one stamen is detached 

 from the rest. As in Genista and the Broom, the jBowers 

 open once for all ; but the elastic power is confined to the 

 upper stamens. In the Broom and in Genista the resist- 

 ance is obtained by the union of the upper edges of 

 the keel. These are also united in Medicago ; but even 

 if they are separated no explosion takes place, the 

 flower being still locked together by four processes, two 

 of which point forwards and two backwards. These fit 

 so beautifully that the proboscis of a humble bee is 

 sufficient to unlock them and release the stamens ; 

 though, according to Henslow, the hive bee is unable 

 to do so. Hildebrand, however, has observed that in 

 the absence of insects it fertilises itself^ The plant is 

 nearly glabrous. 



M. falcata. — In this species the pod is merely curved. 

 The flower is easily exploded, even by flies. 



M. lupulina (Black Medick). — The flowers are minute, 

 but in general structure resemble those of M. sativa. 

 They are mostly fertilised by hive bees, yet how in- 

 finitesimal must be the quantity of honey which they 

 can obtain from so small a flower! This species is 

 annual with us, but becomes perennial in Alpine districts. 

 It is more or less hairy. 



M denticulata. — In this species and some others, 

 especially in Southern regions, the pod is edged with 

 rows of hooked or curved prickles. These no doubt serve 

 to catch hold of any passing animal, and thus facilitate 

 dispersal. They may also be useful in other ways. If 

 the pod is rolled about by wind they would help to 

 attach it as soon as it came to any damp earth. They 

 would also tend to deter birds from eating the seeds. 

 It has been suggested^ that the larger ones prevent 



^ Avebury (Lubbock), British Wild Flowers. 

 * Riviera Nature Notes. By C. C. 



