THE DICOTYLEDOXES 1873 



2. Cyclamineae 



Ovary superior, capsule with valvate dehiscence, flowers with reflexed 

 petals. The plants arise from tubers derived from the hypocotyl. Only 

 genus Cyclamen. 



3. Lysimachieae 



Ovar}' superior, capsule wuth valvate dehiscence or a pyxidium. Corolla 

 lobes contorted in the bud. Lysimachia, Trientalis, Centunculus, Anagallis 

 and Glaux. 



4. Samoleae 



Ovary partly inferior. Only genus Samohis. 



5. Corideae 



Flowers zygomorphic, calyx spiny. Only genus Coris. 



Among the Primuleae the largest genus is Primula, with about 300 

 species. This genus is widely distributed in the north temperate regions, 

 occurring particularly in the mountainous districts of northern India and 

 China. Besides the five species which occur wild in Britain many are 

 cultivated either in gardens or in greenhouses. P. sinensis and P. japonica 

 are among the more important of the greenhouse forms. The genetical 

 nature of these species, and their mutant forms, has formed the subject of 

 very extensive studies carried out in recent years at the John Innes Horti- 

 cultural Institute. As a result of this work, not only has the cytological 

 complement of the species been minutely investigated, but a number of 

 new races of considerable horticultural value have been produced. 



The flowers of Primula (Fig. 1780) are dimorphic and heterostylous. 

 Darwin showed that legitimate pollination, in which the stigma of the long- 



FlG. 1780. — Primula sinensis. Left, thrum-eyed flower. Right, pin-eyed flower. 



