x ii PREFACE TO THE REPRINT OF 1884. 



The following Acanthacese have cleistogamic flow- 

 ers: Stenandrium rupestre, Didipetra assurgens, Ste- 

 monacanthus coccineus, Dianthera sessilis, Blechum 

 Brownei. 



Among other families: Erithalis fruticosa (Eubia- 

 cece), Polystacliya luteola, are also cleistogamic. 



The curious flowers of Pavonia hastata are described 

 by E. Heckel (' Comptes rendus/ Ixxxix. p. 609). This 

 species has cleistogamic flowers, which chiefly differ 

 in appearance from the perfect flowers, in having no 

 nectar-guides; there are, as usual, no nectaries. The 

 pollen is entomophilous in character, and it is said 

 that the tubes are protruded while the pollen is in the 

 anthers. 



F. Ludwig (<Bot. Centralblatt/ 1880, p. 861) men- 

 tions Plantago virginica as producing under cultivation 

 only cleistogamic flowers. 



F. Miiller (' Nature,' xix., 1879, p. 463) shows that 

 the curious submerged Podostomaceae of Brazil produce 

 flowers which are probably cleistogamic. 



Solms-Laubach ('Gb'ttingen Nachrichten/ June, 

 1882) has written an interesting paper on Heteranthera, 

 a plant belonging to the Pontedereacea?. He describes 

 the cleistogamy of some species of the genus, and points 

 out that the form and distribution of the cleistogamic 

 flowers serve as a specific character, without which H. 

 callafolia could not be distinguished from H. Kotsch- 

 yana. 



FRANCIS DARWIN. 



Jan., 1884. 



