140 THE STORY OF THE PLANTS. 



lent example of another form of wind-fertilisa- 

 tion, carried to a still higher pitch of develop- 

 ment. Here the sexes grow on different plants, 

 and the flowers are tiny, green, and inconspicu- 

 ous. The males consist of a calyx of four sepals, 

 each sepal with a stamen curiously caught under 

 it during the immature stage. But as soon as 

 they ripen they burst out elastically, and shoot 

 their pollen into the air around them. In this 

 case, and in many like it, the plant itself helps 

 the wind, as it were, to disseminate its p yllen. 



The common English bur-reed is a waterside 

 plant of great beauty which shows us another 

 interesting instance of wind-fertilisation in an 

 advanced condition (Fig. 28). Here the sepa- 

 rate flowers are very much reduced — as simple, 

 in fact, as those of the cuckoo-pint. The males 

 consist of nothing but stamens, gathered in close 

 globular heads, with a few small scales inter- 

 spersed among them, which seem to represent 

 the last relics of a calyx. The females are made 

 up of single ovaries, each surrounded by three 

 or six scales, still forming a simple rudimentary 

 calyx. They, too, are clustered in round heads 

 or masses on antler-like branches. The plant 

 belongs to the threefold group, and represents 

 a very degenerate descendant of a primitive 

 ancestor something like the arrowhead already 

 described in the last chapter. But the arrange- 

 ment of the heads on the stem is very interest- 

 ing. The balls at the top are entirely composed 

 of male flowers ; those at the bottom are exclu- 

 sively female. The female flowers ripen first, 

 and receive pollen by aid of the wind from some 



