1286 A TEXTBOOK OF THEORETICAL BOTANY 



being borne in separate inflorescences. The staminate inflorescence con- 

 sists of a pendulous catkin up to lo cms. long, bearing about a dozen flowers, 

 each solitary in the axil of a small bract. The catkins themselves are formed 

 in the axils of the uppermost bud scales, or lowest foliage leaves, so that they 

 hang from each opening bud. Each staminate flower consists of a perianth 

 of 5-7 minute, green segments, enclosing 5-12 stamens which are situated 

 more or less opposite the perianth segments. Both filaments and anthers 

 are short and there are no nectaries present. The female inflorescence con- 

 sists of a spike, comprising 2-3 flowers, and borne in the axils of leaves near 

 the end of the twigs. Each flower is surrounded by a cupule of concrescent 

 scales and consists of a perianth of 6 greenish scales surmounting the ovary, 

 which is inferior and syncarpous, with three loculi each containing two 

 ovules with axile placentation. The style is short and stout and bears three 

 stigmas the tips of which curve outwards. 



The pollen is powdery and dry and is produced very freely by the 

 pendulous catkins. It is scattered by the action of the wind. Pollination 

 takes place in May, at which time the ovaries of the female flowers are only 

 rudimentary and the pollen tubes grow slowly down the style, where they 

 wait until late June or early July of the following year before the ovules are 

 ready for fertilization. 



Just as Salix is occasionally wind-pollinated, so certain species of 

 Qiiercus in Malaya are insect-pollinated, the attraction being perfume rather 

 than nectar and pollen presumably the material sought by the visitors. 



2. Pendant Type 



The best example of this type is found in the genus Riimex where the 

 small, pendulous flowers are adapted for wind pollination (Fig. 12 18). In 

 R. crispus three forms of the plant often occur : those with large, herma- 

 phrodite flowers in which the stigma is immersed in the perianth segments ; 

 those in which there are small female flowers scattered among herma- 

 phrodite ones, and lastly those possessing only small female flowers, in 

 which the stigmas project beyond the perianth segments. 



The flowers consist of five or six perianth segments enclosing from 5-9 

 stamens, which surround the ovary. This ovary is unilocular with three 

 styles and a single basal orthotropous ovule. The flowers are protandrous 

 and the anthers project well beyond the limits of the perianth. The flowers 

 being pendulous, the anthers freely discharge their pollen, which is at the 

 same time protected from rain by the perianth. For the same reason self- 

 pollination is prevented as the anthers hang below the stigmas. In the 

 hermaphrodite flowers, only after the anthers have discharged their pollen 

 do the stigmas elongate, their branches projecting widely beyond the peri- 

 anth. In purely female flowers there may be the vestiges of six stamens, 

 suggesting that these monoecious flowers have been derived from herma- 

 phrodite ones. Even in hermaphrodite flowers some of the stamens may be 

 functionless or reduced. Though self-pollination is excluded, geitonogamy 

 may occur, for the flowers are generally arranged in dense panicles. 



