CLEISTOGAMY 55 
Lamium amplexicaule develops cleistogamous flowers twice a year, i.e. in 
spring, before the chasmogamous forms appear, and in autumn, when the weather has 
become cooler. Here again the pollen-grains in the closed flowers send out their 
pollen-tubes to the stigma, either after escaping from dehisced anthers or while still 
in anthers that remain closed; in the latter case the pollen-tubes break through 
the anther-wall. In this case also good fruits are developed. 
According to Hildebrand (‘ Geschlechterverteilung,’ p. 77), many flowers pollinate 
and fertilize themselves cleistogamously under water, in cases where this is so deep 
that the flowers cannot reach the surface. This occurs, e.g., in Ranunculus aquatilis 
(Axell), Alisma natans, Illecebrum verticillatum, Subularia aquatica (Axell), and others. 
Hansgirg (Bot. Centralbl., Cassel, xlv, 1891, 
PPp- 74, 75) distinguishes such flowers as pseudo- 
cleistogamous, as contrasted with genuinely cleisto- 
gamous ones. They completely agree with normal 
open flowers as regards size, form, position, &c., 
and like them possess all the specializations that 
serve for attracting insects. 
In certain circumstances therefore the otherwise 
normally opening chasmogamous flowers remain 
closed, and fertilize themselves. This may be 
brought about: 1. In consequence of deficiency 
of light,— photo-cletstogamous flowers (f); 2 in pig g e ucencammnaaieina bibaes 
consequence of high water-level, or strong current, of Lamium amplexicaule Z. (after Hilde- 
. 5 z brand): a. external view; 4. cut through 
owing to which the flowers remain closed under longitudinally. 
water,—hydro-cleistogamous flowers (A); 3. in con- 
sequence of insufficient warmth,—shermo-cletstogamous flowers (¢). 
Hansgirg (op. cit.) gives a list of all the pseudo-cleistogamous flowers known to 
him, viz. :— 
Ranunculaceae: Ranunculus aquatilis (7). 
Nymphaeaceae: Nymphaea coerulea, N. zanzibariensis, N. madagascariensis 
( or sometimes 4), Victoria regia (ditto), Euryale ferox (ditto). 
Portulacaceae: Montia fontana (f or sometimes /). 
Caryophyllaceae: Stellaria media and var. pallida (S. Boraeana), S. cerastoides, 
Spergularia rubra; Spergula pentandra, arvensis, vernalis, salina, marginata; Malachium 
aquaticum, Holosteum umbellatum, Cerastium arvense, Moenchia erecta; Sagina 
Linnaei, decandra and var. micrantha, apetala (all p or sometimes /); Ilecebrum 
verticillatum (4). 
Oxalidaceae: Oxalis stricta, corniculata, Lasiandra, incarnata, lobata, Deppii 
(all # or sometimes 7). 
Cruciferae: Subularia aquatica (A). 
Droseraceae: Drosera rotundifolia, intermedia (p or sometimes 7). 
Compositae: Taraxicum officinale (f or sometimes /). 
Scrophulariaceae: Veronica hederaefolia, serpyllifolia, agrestis, triphyllos (g or 
sometimes /). 
Primulaceae: Hottonia inflata (A). 
Acanthaceae: Dicliptera assurgens (/). 
