ANGIOSPERM^, DICOTYLEDONES. 785 



a schizocarp (Callitriche; see p. 427, figs. 322 ^ and 322*) or a drupe covered with a 

 thin coat of pulp; it becomes detached from the receptacle. In the Water Chestnut 

 {Trapa natans; see vol. i. p. 607, fig. 144) the two whorls of two sepals each which 

 are adnate to the ovary become a part of the fruit, and their apices project in the 

 form of four stifi" points. The Hygrobia3 are distributed in every quarter of the 

 globe, but belong especially to the North Temperate Zone. The Gunneracese 

 inhabit the Southern Hemisphere. Fossil remains of a plant resembling Myrio- 

 phyllum have been found in strata of the Tertiary Period. The number of extant 

 species known is about 100. 



Alliance LXII. — Passiflorales. 



Families: Passifloraceoi, Loasacece, Datiscacece, Samydacece, Tiirneraceoe, 



PapayaceoB. 



Annual or perennial herbs, shrubs, and trees, with palmately-lobed foliage-leaves. 

 Venation palmate (radiating). Flowers hermaphrodite or pseudo-hermaphrodite, 

 and dioecious; actinomorphic. The floral-leaves spring from a cup-shaped hypan- 

 thium in one or two 4-5-merous whorls. The gynseceum is composed of 3 connate 

 carpels. The unilocular ovary is free, and is raised upon a more or less elongated 

 stalk from the bottom of the receptacle, or else it is sessile and adnate to the cup- 

 shaped receptacle either half-way from the base or from base to toj). The ovules 

 are borne upon three placentas which project in the form of cushions from the 

 internal wall of the ovary. The andrcecium is composed of 4-5 stamens which 

 spring from the edge of the cup-shaped hypanthium. The fruit is a berry or a 

 capsule opening by valves. The seeds contain a fleshy endosperm, in which is 

 imbedded a straight embryo. 



The Datiscacese have a sepaloid perianth. In the Loasacese and Passifloracese 

 the floral-leaves are in two whorls, both of which are petaloid. In the Passiflorace« 

 a many-membered corona is inserted between the androecium and the petals. 

 The Passiflorales belong chiefly to tropical America. Fossil remains have not been 

 identified with certainty. The number of extant species known is about 700. 



Alliance LXIII. — Pepones. 



Families: Ciicwrhitaceoe and Begoniacece. 



Annual and perennial herbs and under-shrubs (sufi"rutices). Venation of the 

 foliage-leaves radiating (palmate). Flowers solitary or in cjmies; actinomorphic; 

 pseudo-hermaphrodite, monoecious and dioecious. The uppermost part of the 

 receptacle, which is deeply hollowed, is developed as a hypanthium, and from it 

 spring the floral-leaves in 1-2 whorls of 2-5 segments each. When two whorls are 

 present they are either both petaloid in colour or the under whorl is a calyx and the 

 upper a corolla. The petals are either free or partially coherent. The ovary is 

 inferior. The ovules are borne on thick pads which are split in two longitudinally, 



VOL. II. 100 



