1 9 1 q] stou T—IN TERSEXES 1 1 1 



of the bog myrtle or sweet gale {Myrica Gale). This plant is a 

 small shrub which grows abundantly in swamps and heaths in 

 Europe, Asia, and the northern part of North America. The 

 species is described as strictly dioecious, and until 1901 no obser- 

 vations that it is ever otherwise have apparently been recorded. 

 Davey and Gibson find that in the peat moors of England there 

 are everywhere present intersexes, or, as they call them, "mixed 

 plants" of many gradations. Judged as a whole, the plants pre- 

 sent every gradation of intersexes between dioecism, monoecism, 

 and hermaphroditism. The variations seen in the various catkins 

 on a single plant include the entire range, and all the grades may 

 appear among the flowers of a single catkin. Furthermore, a 

 study of individual plants for a series of years shows that changes 

 of sex from year to year occur. Plants entirely female in 1913 

 were entirely male in 1914. Plants female in 1913 were mixed in 

 1914, entirely or nearly all male in 191 5, and again female in 

 1916. 



Davey and Gibson point out that the changes in sex seen in 

 Myrica Gale indicate that sex determination is here in some way 

 associated with environmental conditions. In regard to this they 

 state as follows : 



The conditions which naturally suggest themselves are moisture, tem- 

 perature, and light (with their influence on nutrition), and also the previous 

 state of a plant as regards the production of fruit. Since the staminate 

 flowers are developed early in the season preceding that in which they flower, 

 while the pistillate catkins develop much later, it is possible that conditions 

 accelerating or retarding the development of catkin buds may influence the 

 proportions of the two kinds (pp. 150-151). 



The facts reported for Myrica Gale are striking and suggest 

 that similar conditions may already be present or may spontane- 

 ously arise in other species now considered as dioecious. 



Intersexes in Plantago lanceolata 



This species is a native of Europe and Asia. It has been 

 introduced into America, where it has spread from the Atlantic 

 to the Pacific, through Canada, and southward in the United 

 States to Florida. It is well known as a vigorously growing 

 species which in many sections has become a troublesome weed. 



