



x ii PREFACE TO THE REPRINT OF 1884. 



The following Acanthaceas have cleistogamic flow- 

 ers: Stenandrium rupestre, Diclipetra assurgens, Ste- 

 monacanthus coccineus, Dianthera sessilis, Blechum 



Brownei. 



Among other families: Erithalis fruticosa (Rubia- 

 cece), Polystachya luteola, are also cleistogamic. 



The curious flowers of Pavonia hastata are described 

 by E. Heckel (' Comptes rendus/ lxxxix. 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 Podostomacege of Brazil produce 

 flowers which are probably cleistogamic. 



Solms-Laubach (' Gottingen Nachrichten/ June, 



1882) has written an interesting paper on Heteranthera, 



a plant belonging to the Pontedereaceae. 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. 



callcefolia could not be distinguished from H. Kotsch- 

 yana. 



Francis Darwin. 



Jd7L, 188%. 



