THE DICOTYLEDONES 



1811 



most live on trees. Some species are unselective, others can only live on 

 the wood of one or two species. The vegetative parts of Arceuthohium are 

 endophvtic in the host plant, as in the Rafflesiaceae. 



Fig. 1707. — ViscHin album. Flowers. A, Male flower. B, Female 



flower. [After Hiitchitisan.) 



The flowers (Fig. 1707) are dimerous, or trimerous, the parts being 

 either free or united. In some genera, included in the sub-family Viscoideae, 

 the flowers are small and inconspicuous, while in the Loranthoideae they 

 may be large and brilliantly coloured. The stamens are equal in number 

 to the segments of the corolla and the anthers consist of a large number of 

 separate pollen sacs. The ovary is unilocular with a large central placenta 

 bearing numerous ovules. 



The Balanophoraceae are a small family of root parasites which are 

 leafless and devoid of chlorophyll. There are fifteen genera and forty 

 species which are typically tropical in distribution. The plant (Fig. 1708) 

 is attached to the roots of its host by suckers developed from an under- 

 ground tuberous stem. From it springs the inflorescence, though in some 

 species the flowers may develop within this tuber and break out through 

 it. The inflorescence grows up above the soil in the form of a spike or head, 

 beset with scale leaves, and bears unisexual flowers. The male flowers have 

 a perianth of three or four parts which are united into a tube, with an equal 

 number of stamens. The female flowers are generally devoid of any 

 perianth segments and consist of a gynoecium composed (Fig. 1709) of 

 one to three carpels which unite to form a unilocular ovary. The ovules 

 are naked and may be reduced to embryo sacs embedded in a common 

 mass of tissue called the mamelon. Little is known about the pollination 

 mechanism, but one, SarcopJiyte sangiiinea, emits the smell of decaying 

 fish and mav be visited bv insects. Others are thought to be also entomo- 

 philous. 



The largest genus is Balarwphora, which contains eleven species 

 scattered through Indo-Malaya, Polynesia and Australia. 



The Santalaceae are semi-parasitic herbs, shrubs or trees with green 

 leaves, some of which live as epiphytes, others as root parasites. The only 



