SECT. 11 



PHANEROGAMIA 



567 



Family 2. Buxaceae. Characterised by a loculicidal capsule, and a dorsal raphe 

 to the seed. Buxus sempervirens, the Box, is a poisonous evergreen shrub with 

 very close wood, native of Southern and Western Europe. In the a.xils of small, 

 decussate bracts stand capitate inflorescences, consisting of a terminal, trimerous 

 female flower, and a number of tetramerous male flowers. 



Order 10. Centrospermae 



Herbs, less commonly small Avoody plants. Flowers with few 

 exceptions hermaphrodite and tri- or penta-merous. Perianth and 

 androecium consisting of one or two whorls. Sometimes numerous 

 stamens. Ovary superior, unilocular, with a single basal ovule or 

 with a free central placenta bearing a number of ovules with very 

 long funicles. 



eum nfficinalc. J, Flower; B, the same cut througli longitudinally; 

 with disc. Eheum compiwtum: D, fruit. (After Lurssen, magnified.) 



Family 1. Polygonaeeae. — For the most part perennial herbs, 

 Avith hollow stems swollen at the nodes, and alternate, simple leaves. 

 The membranous stipules of the latter are coherent to form a 

 sheath or OCHREA protecting the terminal bud ; when broken through 

 by the growth of the stem, this remains as a tubular sheath around 

 the lower part of the internode (Fig. -545). The hermaphrodite flower 

 is typically trimerous, but a larger number of members sometimes 

 occurs in the perigone or the androecium. Ovary superior, formed 

 of three carpels, unilocular, with a single, basal atropous ovule. Fruit 

 in nearly all cases a triangular nutlet. 



Mainly natives of the N. Temperate zone. 



Genera. — Ilhnim, Rhubarb. This is an East Asiatic genus, with large, radical 

 leaves and a large,. spreading, paniculate inflorescence (Fig. 546). Leaves simple, 

 cordate-reniform, with palmate venation, sometimes more or less lobed. The flower 

 lias a perigone of two similar wh 3rls, and two whorls of stamens, the outer whorl 

 being double by chorisis ; P3 + 3,A6+3, G (3). Nectar for visiting insects is 

 secreted by the large scales of the disc. The triangular ovary becomes winged as 



2 2 



