278 CISTINEJE. [part ii. 



differ chiefly in the capsule, which in the latter 

 genus is triangular and one-celled, opening into 

 three valves, each of which has a narrow dissepi- 

 ment down its centre. To prevent any con- 

 fusion arising from the use of these terms, I may 

 here observe that when a capsule is divided into 

 several cells, having no communication with 

 each other, the membranes that separate them 

 are called dissepiments; while the nerve-like part 

 of it to which the seeds are attached is named 

 the placenta. Sometimes the placenta is 

 merely a nerve running down the side of the 

 capsule, when the capsule is one-celled, without 

 any dissepiment or division ; and sometimes the 

 dissepiment does not spread across the capsule 

 so as to divide it into different cells, but only 

 projects a little way from the side towards the 

 centre, as in the one-celled capsule of the Poppy, 

 (see p. 260,) and in that of the Helianthemum, 

 when the seed-vessel opens naturally into differ- 

 ent parts, as in the Gum Cistus, these parts 

 are called valves, as are also the parts of pods, 

 as sho^\Ti in the curied-up valves of the silique, 

 Jig. 115, in p. 268. 



To return to the Helianthemum, the species 

 of this genus are generally used for rockwork, 

 as they are all dwarf plants, though many of 

 the genus Cistus are large shrubs four or five 

 feet high. The English name of the Helian- 



