58 BRITISH FLOWERING PLANTS chap. 



and 8-12 petals. The carpels are rather large, in a 

 globular head, and smooth. The structure of the flower 

 resembles that of the preceding species and of R. acris. 

 The number of stamens varies considerably. The flowers 

 are generally sterile, though the visits of insects are 

 numerous, and the plant generally propagates itself by 

 the tubers. It is a remarkable fact that this species, 

 which flowers so freely, rarely sets its seeds. Some 

 specimens produce purely female flowers. The plant 

 is found throughout Europe and in Western Asia and 

 North Africa. 



R. hirsutus has a stem 6-8 inches in height. It 

 agrees with R. bulbosus in its foliage, and in having the 

 sepals reflexed, but the flowers are paler, smaller, and 

 more numerous. The hairs are spreading or reflexed ; 

 and the achenes have a series of tubercles within a 

 broad margin. The pollen is yellow, round or oval, 

 with three longitudinal furrows, and 30-37 /x in diameter. 

 Warnstorf says that the flower produces no honey. 



R. arvensis (Hunger-weed, Starve-acre). — An unde- 

 sirable cornfield weed, which flowers and seeds with the 

 wheat. It is an erect, branching, glabrous annual, 6-18 

 inches high. The upper leaves are deeply cut into 

 three linear -lanceolate lobes. The pale yellow flower is 

 very characteristic of this species, which also diff"ers 

 from the preceding species in having the achenes large, 

 few, flattened, and covered on both sides with straight 

 or often hooked prickles, which contribute to the dis- 

 semination of the seeds. It varies considerably in the 

 number of stamens and carpels. Some of the flowers 

 contain no stamens. 



Caltha 



This genus contains but few species, only one of 

 which is British. The name is derived from the Greek 

 word KdXa0o<;, a cup, suggested by the golden cup-like 

 flower, to which also we owe the common name King- 

 cups. 



Caltha palustris (Marsh Marigold or King-cups) is a 



