760 



THE SUBDIVISIONS OF THE VEGETABLE KINGDOM. 



aromatic substances (lupulin and hashish) are produced in special cells and groups of 

 cells The curious tabular and columnar roots of the Ficaceae have been described 

 in detail and illustrated in vol. i. pp. 755-757. Here is represented a Ficus (fig. 428) 

 with aerial roots, which Hooker saw used by the natives in the Himalaya as bridges. 

 "The property of the fig-roots, which inosculate and form natural grafts, is taken 

 advantage of in bridging streams, and in constructing what are called 'living bridges' 

 of the most picturesque forms." The axis of the inflorescence is thickened in many 

 cases, notably in the Dorsteniacese, Artocarpaceae, Ficacese, Conocephalacese, and 



Fig. 430. The Oak (Quercus sessiliflora). 



i Cluster of female flowers. 2 Single female flower. Longitudinal section of a female flower showing the ovary with ovules, 

 small perianth and the young cup or cupule. * Three male flowers. * Cluster of nuts (acorns) with their cupules. The 

 seed, i Longitudinal section of seed. 8 Transverse section of seed. l , 2 , 8 , * enlarged ; rest nat. size. 



Moracese; sometimes it is discoid, and sometimes hollowed out into the shape of an 

 urn (see p. 157). It also enters into the structure of certain fleshy succulent collec- 

 tive fruits, which afford such an important article of food in hot countries, viz. the figs 

 of Ficus, and the Bread-fruit of Artocarpus incisa. Sometimes the perianth also 

 takes part in the formation of the fruit, as, for instance, in the Mulberry (Morus), 

 where it is converted into a fleshy envelope inclosing the fruit. On the other hand, 

 in several other Viridiflorge the perianth is almost completely suppressed. In 

 Dorsteniacese and Moraceae the stamen-filaments are inflexed in the bud, and spring 

 up after the perianth has opened, scattering the pollen-dust in the air (see fig. 229, 

 p. 137). The filaments are straight in the flowers of the other families. The embryo 

 is curved in most cases. There is either a very small quantity of endosperm or none 

 at all. The Viridiflorae are found in all parts of the world. The Ulmacese extend 



