i6io A TEXTBOOK OF THEORETICAL BOTANY 



Fig. 1462. — Nxmphaea alba. Flower in vertical section. (After Caspary in Engler- 



Prantl.) 



(Fig. 1463) are dissected but the floating leaves are circular, the latter 

 being produced only at the flowering season. In the latter sub-family there 

 are no submerged leaves for all grow up to the surface during the growing 

 period and all are entire. It is to this sub-family that all the Water Lilies 

 belong. 



The Berberidaceae, or Barberry Family, comprise a small number of 

 genera most of which are deciduous shrubs. There are about 200 species 

 in north temperate regions. They are either shrubs or perennial herbs. 

 The flowers are hermaphrodite and are produced in racemes. The perianth 

 may consist of four whorls of three segments each, which are followed by 

 two whorls each of three stamens. The anthers are introrse and open by two 

 valves. There is a single carpel with one or numerous ovules. The fruit is 

 a berry. The chief genus is Berberis, with 190 species, of which B. vulgaris 

 (Barberry) is wild in Britain. The pollination mechanism is unusual and 

 worthy of special reference. The inner surface of the base of each stamen 

 is sensitive to contact and the stamens at rest stand out, away from the ovary. 

 Nectar is secreted at the base of the two inner whorls of perianth segments. 

 An insect searching for this nectar, on touching the stamens causes them to 

 spring inwards, violently shaking their pollen on to its head. In this 

 position the pollen will come into contact w4th the stigma when the next 

 flower is visited. Many species are cultivated on account of their bright 

 yellow flowers and red berries. Some are evergreen such as B. aqiiifolium, 

 with pinnate leaves, now often separated in the genus Mahunia (Fig. 1464), 

 others are deciduous and provided with leaf spines which represent the 



