448 D1COTYLEDONES. 



with one style and one erect ovule in each loculus. The fruit is 

 most frequently a drupe. The embryo is large, often green or 

 yellow, with endosperm. 



Bhamnus (Buckthorn) has a juicy drupe with 3 (2-4) stones, 

 surrounded at the base by the persistent portion of the receptacle ; 

 the disc is thin. R. cathartica (common Buckthorn) : dioecious, 

 with opposite, serrate leaves. R. frangula (Alder Buckthorn) : 

 flowers $ , with scattered, entire leaves. Ceanothus (N. Am., with 

 richly-flowered inflorescences and a fruit closely resembling that of the 

 Euphorbias). Phylica, Pomaderris (Austr., fruit a capsule). Zityphu8,FaUuru<t, 

 Colletia (S. Am.) are thorny sbrubs ; C. spinosa has thorny shoots with small, 

 caducous leaves ; the seedling has normal foliage-leaves. Others climb by 

 tendrils as in the Ampelidacese, e.g. Gonania. 



FIG. 482. Rhamnus cathartica: A long-styled <J -flower; pet petals; B short-styled 

 <J -flower ; C long-styled ? -flower; D short-styled ? -flower (after Darwin). 



475 species, 40 genera ; chiefly in temperate and tropical climes. Some are 

 medicinal plants, the bark and fruit having purgative properties (the bark of 

 Rhamnus frangula and " Cascara Sagrada " from the bark of B. purshiana are 

 officinal). The fruits and seeds of others are edible, for example, the fruits of 

 Zizyphus lotus, Z. vulgaris, Z. spina Christi, etc. Green and yellow dyes are 

 obtained from the fruit of jR cathartica, infectoria and others (Avignon grain). 

 Ceanothus-, Rhamnus- and evergreen Phylica-syeciea are ornamental shrubs. 



Family 18. Thymelaeinae. 



Exclusively trees or shrubs with simple, entire, scattered leaves 

 without stipules. They have a strongly perigynous, regular, 4- 

 merous flower. The receptacle (often coloured) envelopes a simple 

 gynoeceum formed of 1 carpel and with, in most cases, 1 ovule, bear- 

 ing on its edge 4 (or 5) petaloid sepals and, but rarely at the same 

 time, small, scale-like petals. The corolla is most frequently 

 entirely wanting (and hence these plants were formerly reckoned 

 among the Monochlamydeee) ; frequently only one of the 2 whorls 

 of stamens, which are situated on the inner side of the edge of the 

 receptacle, is developed. The fruit is most frequently a \-seedea 



