174 PLANT LIFE 



This species of Lychnis is a dioecious plant. 

 That is to say, the flowers of some plants are 

 exclusively female whilst the rest are ex- 

 clusively male. The unisexual character is 

 produced by the abortion of the pistil in the 

 flowers of the male, and of the stamens in 

 those of the female plants. The fungus only 

 reaches maturity and produces its violet 

 powdery spores in the stamens. So far as 

 the male plants are concerned there is no 

 difficulty, but with the female flowers it is 

 otherwise. What the fungus does when it 

 attacks the latter is to stimulate the plant to 

 produce stamens exactly like those of a male 

 flower. The mycelium grows sparsely in 

 them until the pollen sacs are approaching 

 maturity, then it suddenly breaks out into 

 virulence and destroys the pollen-producing 

 tissues, filling up the space with its own spores. 

 Nor does the influence of this remarkable 

 parasite stop here, for the pistil is arrested 

 at an early stage of its development and in 

 certain other structural characters the flower 

 closely approximates to that characteristic 

 of a male plant so closely indeed that very 

 careful experiments were needed to clear up 

 the matter. 



It is not known what the substance formed 

 by the fungus, and responsible for the change, 

 really is. All attempts to imitate its action, 

 and to produce a similar result artificially 

 have so far proved unsuccessful. 



The somewhat common " witches'-brooms " 



