56 INTRODUCTION 



Gentianaceae : Menyanthes sp. {h). 



Scleranthaceae : Scleranthus annuus {p or sometimes /). 



Alismaceae : Alisma natans {h). 



Butomaceae : Hydrocleys nymphoides {h or sometimes p). 



Juncaceae : Juncus bufonius and effusus {p or sometimes /). 



Glumaceae : Triticum Spelta, species of Stipa, Hordeum distichum, &c. (/). 



The following pseudo-cleistogamous species should be added to those in 

 Hansgirg's list. Most of them remain closed in dull or rainy weather): 



Papaveraceae : Hypecoum pendulum Z. (Kerner). 



Cruciferae: Arabis coerulea Haenke (Kerner), Nasturtium officinale R. Br. 

 (Knuth). 



Caryophyllaceae : Cerastium semidecandrum Z. (H. Miiller), C. tetrandrum 

 Curt. (Knuth), Sagina nodosa Fzl. (Warming), S. procumbens Z. (Schulz, Warming). 



Hypericaceae : Hypericum humifusum Z. (Kerner). 



Geraniaceae : Erodium maritimum L'H&. van apetalum (Ludwig). 



Scleranthaceae : Scleranthus annuus Z. (under the snow in winter, Schulz). 



Portulacaceae : Portulaca oleracea Z. (Kerner), Montia minor Gmel. (Kirchner). 



Rubiaceae : Galium uliginosum Z. (Schulz). 



Compositae : Filago minima (Errera and Gevaert). 



Campanulaceae : Campanula uniflora Z. (Warming). 



Gentianaceae : Gentiana prostrata Ke. and G. tenella Rottb. = G. glacialis Vill. 

 (Kerner), G. campestris Z. (Kerner), Cicendia filiformis (Errera and Gevaert). 



Scrophulariaceae : Veronica peregrina Z., V. arvensis and V. persica Pcir.'=- 

 V. Buxbaumii Ten. (Kirchner), Limosella aquatica Z. (hydro-cleistogamous, Kerner). 



Primulaceae : Centunculus minimus Z. (Ascherson). 



Polygonaceae : Polygonum Hydropiper Z. (Kerner), P. minus Huds. and P. mite 

 Z. (Kerner), 



Thymelaeaceae : Passerina annua Z.=Stellera Passerina Z. (Kerner). 



Iridaceae : Sisyrinchium anceps Lavi. (Kerner). 



Liliaceae : Gagea lutea (Kerner). 



Gramineae : Avena sativa Z. (Hildebrand), Bromus secalinus Z. (Hildebrand), 

 Hordeum distichum Z. (Delpino), H. Zeocrithron (Hansgirg), Secale cereale Z. 

 (ditto). 



A few more cases have still to be mentioned in which cleistogamy is induced 

 by prolonged drought, and in which it disappears again on placing the plants in a 

 moister situation. Baron E. Eggers (Bot. Centralbl., Cassel, viii, 1 88 1 , pp. 5 7-9) places 

 in this category the following St. Croix species : Sinapis arvensis Z. ; Acanthaceae, 

 Stenandrium rupestre Ns., Dicliptera assurgens Gris., Stemonacanthus coccineus 

 Ns., Dianthera sessilis Gris. and Blechum Brownei Juss.; Rubiaceae, Erithalis 

 fruticosa Z. ; and the orchid Polystachya luteola Hook. 



Errera and Gevaerl (Bull. Soc. roy. bot., Gand, xvii, 1878) observed the 

 opposite of this in Subularia aquatica, which was cleistogamous in a marshy situation, 

 but became chasmogamous when placed in a dry locality. 



According to Henslow (' On the Self-fertilization of Plants,' Trans. Linn. Soc. 

 (Bot.), series 2, i, 1877, pp. 317-48) cleistogamy is induced by lack of warmth in 



