56 INTRODUCTION 
Gentianaceae: Menyanthes sp. (A). 
Scleranthaceae: Scleranthus annuus (p or sometimes 7). 
Alismaceae: Alisma natans (2). 
Butomaceae: Hydrocleys nymphoides (# or sometimes £). 
Juncaceae: Juncus bufonius and effusus (f 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 Aaenke (Kerner), Nasturtium officinale R. Sr. 
(Knuth). 
Caryophyllaceae: Cerastium semidecandrum Z. (H. Miiller), C. tetrandrum 
Curt. (Knuth), Sagina nodosa /2/. (Warming), S. procumbens Z. (Schulz, Warming). 
Hypericaceae: Hypericum humifusum Z. (Kerner). 
Geraniaceae: Erodium maritimum Z’ er, var. 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 Ae. and G. tenella Ro//d.=G. glacialis Vz. 
(Kerner), G. campestris Z. (Kerner), Cicendia filiformis (Errera and Gevaert). 
Scrophulariaceae: Veronica peregrina Z., V. arvensis and V. persica Pozr.= 
V. Buxbaumii Zen. (Kirchner), Limosella aquatica Z. (hydro-cleistogamous, Kerner). 
Primulaceae: Centunculus minimus Z. (Ascherson). 
Polygonaceae: Polygonum Hydropiper Z. (Kerner), P. minus Huds. and P. mite 
LZ. (Kerner). 
Thymelaeaceae: Passerina annua Z.=Stellera Passerina Z. (Kerner). 
Iridaceae: Sisyrinchium anceps Zam. (Kerner). 
Liliaceae: Gagea lutea (Kerner). 
Gramineae: Avena sativa Z. (Hildebrand), Bromus secalinus Z. (Hildebrand), 
Hordeum distichum JZ. (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, 1881, pp. 57-9) places 
in this category the following St. Croix species: Sinapis arvensis Z.; Acanthaceae,— 
Stenandrium rupestre JVs., Dicliptera assurgens Grzs., Stemonacanthus coccineus 
NVs., Dianthera sessilis Grzs. and Blechum Brownei /uss.; 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 
