PREFACE TO THE REPRINT OF 1884. yii 



xxiv., 1882) states that the TurneraceaB contain a large 

 proportion of dimorphic plants. His monograph on this 

 family I know only from the abstract in the { Botan. 



Centralblatt/ p. 207. He has, made the following in- 

 teresting observations : — " In the TurneraceaB the dimor- 

 phic species tend to be perennials, with conspicuous flow- 

 ers, while the monomorphic species have smaller flowers, 

 and are chiefly annuals." He states that a tendency 

 to dimorphism in the monomorphic species expresses 

 itself only in elongation of the style. 



In the subjects kindred to those considered in Chap- 

 ter VII, rather more work has been done. 



F. Ludwig (* Zeitschrift f. d. gesam. Naturwiss.,' 

 1879, p. 44) describes three plant-forms in Plantago 

 lanceolala, 



1. Hermaphrodites with white anthers. 



2. Semi-females, with small shrivelled yellow an- 

 thers, containing a small quantity of pollen, of which 

 many grains are bad. 



3. Purely female form. 



Ludwig has noticed the tendency described by Del- 

 pino to entomophily in Plantago, the flowers being often 

 fairly conspicuous, and are visited by insects. 



Ludwig draws some interesting general conclusions 

 on Gynodicecious plants. 



1. They are all more or less dichogamic. 



2. In the protandrous forms the females are more 

 numerous at the beginning of the season. In the pro- 

 togynous forms the reverse is the case. 



3. Abortive anthers often degrade into perianth seg- 

 ments. 



4. He confirms the received opinion that female flow- 

 ers are smaller than hermaphrodites. 



He discusses the origin of dioeciousuess, assigning 



1 



