254 THE STORY OF PLANT LIFE 



leaves, a member of the Yam family, or Dioscoraceae. 

 Both are dioecious plants, that is, with unisexual 

 flowers, the male flowers on a different plant to that 

 bearing the female. Both have twisted underground 

 rhizomes, which have been employed as a substitute 

 for mandrake or Mandra^ora. 



As a dioecious plant White Bryony is dependent 

 upon insects for pollination, and cannot be self- 

 pollinated. The type of insect which pollinates it 

 on the Continent is not common in this country. 

 The White Bryony does not grow in Scotland or very 

 largely in Wales, and it is in those districts that 

 these insects are scarce. The correlation between 

 insect distribution and that of certain plants is 

 similar in other cases where a plant is specially 

 adapted to a particular type of insect. 



The White Bryony is an English plant, not. found 

 in the North of England. It is found in the Channel 

 Islands, but does not occur in Ireland. 



The habitat is hedges, thickets, and it is abundant 

 on chalky soils, on chalk scrub, etc. 



The plant is a climber, with sensitive, simple or 

 branched, spirally twisted tendrils, which revolve, and 

 may interlock or become released. The tendrils are 

 modified leaves. The rootstock is thick, tuberous, 

 fleshy, branched. The plant has a disagreeable, milky 

 juice, and when dry a sickly odour, perhaps attractive 

 to flies. The annual stems climb to a great height, 

 and are slender, angled, annular. The plant is rough, 

 with very small hairs. The leaves are stalked, palmate. 



