TURNIP TRIBE. ROCK-ROSE TRIBE. 373 



was so great, that lie would often allow them to use no other 

 kind of fresh vegetable food than grass. If he had been 

 acquainted with the simple fact, that none of the Cruciferse are 

 deleterious, and that all possess (in a greater or less degree) those 

 properties which render them more valuable than any ordinary 

 medicines in the treatment of this disease, he might have been 

 able to restore many to health, by simply explaining to them the 

 very evident marks by which this order is characterised, and 

 encouraging them to seek for plants which exhibit such, and to 

 make use of them without apprehension. 



536. The Order CISTACE^, or Rock-Rose tribe, must next be 

 mentioned. Although not a numerous or very important group, 

 it presents several points of interest. The plants it contains 

 flourish in dry rocky places, where others would not find a due 

 supply of fluid nutriment ; and these they ornament with a pro- 

 fusion of blossoms, having brilliant colours. They usually expand 

 in the night, and after a few hours' exposure to the sun, they 

 perish. A few species (belonging to the genus Helianthemum} 

 are natives of this country ; and others, introduced from the 

 South of Europe, are cultivated as evergreen bushes in shrub- 

 beries, or are employed to ornament rough banks and masses of 

 rock-work, over which they trail with great beauty. In the 

 general characters of their flowers, they may be regarded as 

 intermediate between the Papaveracese, and the Violacese the 

 order to be next described. The sepals of the calyx are five ; 

 but these do not exactly form a single regular whorl, as two 

 arise somewhat lower than the others, and are somewhat exter- 

 nal to them. The corolla usually consists of five petals, which, 

 from the manner in which they are packed within the bud, have 

 a crumpled appearance when the flower unfolds ; they fall off at 

 an early period of flowering, whilst the calyx remains as a pro- 

 tection to the seed-vessel. The stamens are hypogynous, and 

 indefinite in number ; and they are usually much shorter than 

 the petals. The ovary is superior, and is either one- celled with 

 parietal placentae, or is divided into five or ten cells by partitions 

 radiating towards a centre. There is never more than one style, 

 and this terminates in a simple expanded stigma. The fruit is a 



