INTRODUCTION 



XXXVll 



four truly British species, only one, H. Cham(Ecisii(s, is at all 

 common. The prostrate growth, small stipules, and green upper 

 surfaces of its leaves at once show us that it is to this species, the 

 Common Rock-Rose, that our specimen belongs. 



We mav find a second example to test at no great distance. It 

 is an erect, herbaceous plant with smooth leaves and long racemes 



heliAnthemum cham^^xistus 

 {Common Rock-Rose). 



TJES^DA LUTEOLA 

 {Dyer's Rocket). 



of green flowers. Here again the veins and stipules of the leaves 

 and the four sepals and petals, though the latter are so cut up as 

 to be difficult to count, suggest a Dicotyledon. The numerous 

 stamens spring from a relatively large, fleshy out. rowth or "disk," 

 which is hypogynous, but by its one-sided development renders 

 the flower monosymmetric. The ovary is distinctly superior, 

 springing from the top of this disk and is three-sided externally 



