THALAMIFLOR.E I2i 



light, or the direction of the incident rays of hght, on 

 the direction of growth. Some flowers respond to 

 the stimulus of light on the direction of their growth 

 by turning towards the light, and are called positively 

 heliotropic. The Rock-rose is one of these, and for 

 this reason it was called Helianthemum [helios, sun, 

 anthemos, flower). It seems to have been named 

 Rockrose from its predilection for stony and rather 

 dry ground. 



The plant is found commonly in England and 

 Eastern Scotland, but not in Ireland. It grows up 

 to an altitude of 2000 ft. 



Wherever there is chalk or limestone, limestone 

 scrub, calcareous grassland or limestone grassland, 

 chalk grassland, or chalk pasture, the Rockrose will 

 be found. It is also found where igneous rocks crop 

 out where there are lime felspars, the two floras being 

 closely akin in some respects. The habitat is thus 

 dry hilly pastures and meadows. 



In habit the Rockrose is a prostrate, spreading 

 undershrub. The stem is short and woody. The 

 flowering branches are annual and prostrate or 

 ascending. The leaves are shortly-stalked, opposite, 

 green, with hairs above, white and downy below ; 

 the borders flat or nearly so, oblong or ovate to lance- 

 shaped, but vary in shape and the amount of 

 pubescence. There are linear to lance-shaped 

 stipules. Lord Avebury found that where the leaves 

 are broad at the base, and thus capable of protecting 

 the buds in their axils, there are no stipules. But 



