CLEISTOGAMY 57 
Tradescantia erecta, Stellaria media, Spergula arvensis, Cerastium glomeratum, 
Gaura parvifolia, Paronychia bonariensis, Corrigiola littoralis, Scleranthus annuus, 
Herniaria glabra, Malva rotundifolia, and others; according to Mechan (Bull. Torrey 
Bot. Cl., New York, x, 1883) in Nemophila maculata Benth., Opuntia leptocaulis DC.; 
according to Coulter (Bot. Gaz., Chicago, viii, 1883) in Cyclamen europaeum; 
according to Bush (op. cit., vii, 1882) in Malvastrum angustum; and according 
to Battandier (Bul. soc. bot., Paris, xxx, 1883) in Portulaca oleracea Z., and others. 
These various forms of pseudo-cleistogamy point to the causes of genuine 
cleistogamy: deficiency of light, air, warmth, dryness, or moisture are to be 
regarded as such. Darwin referred the origin of cleistogamous flowers to 
developmental retardation of chasmogamous forms, due partly to deficiency, but 
also partly to an excess of light, and perhaps also to lack of insects (cf. my note 
on p. 54): 
Observation actually proves that even genuine cleistogamy may be produced 
by deficiency of light. Kerner (‘ Nat. Hist. Pl.” Eng. Ed. 1, II, p. 395), for instance, 
noticed that Viola sepincola does not form any open flowers in the deep shades 
of woods, but does form them in open country in situations that from time to 
time receive sunlight. The investigations of Véchting (Jahrb. wiss. Bot., Leipzig, 
XXv, 1893) agree with this, as he proved experimentally that with feeble illumination 
there is frequent degeneration of the conspicuous parts, and formation of cleisto- 
gamous flowers. And he also is of opinion that defective illumination is of primary 
importance in the evolution of cleistogamy. 
The question whether there are plants which bear cleistogamous flowers only was 
at first answered in the affirmative. A. Batalin (Bot. Ztg., xxix, 1871, pp. 388-92) 
maintained that Juncus bufonius is regularly self-fertilized, its flowers always remaining 
closed. It was, however, established by Ascherson (op. cit., 1871, pp. 551-5; 1872, 
pp. 697-9, 738, 739), Buchenau (op. cit., 1871, pp. 845-52), and Haussknecht 
(op. cit., pp. 802-7) that while numerous flowers fade with enclosed pistil and 
anthers, others on the contrary open out to 180° in a stellate way, so that they 
may also be fertilized by foreign pollen; and it was also shown that between 
these two kinds of flower there are numerous intermediate forms (cf. F. Buchenau, 
‘Bestaubungsverhiltnisse der Juncaceen,’ Jahrb. wiss. Bot., Leipzig, xxiv, 1892, 
PP. 363, 364, 382). 
There is also an African species of Salvia which was at one time supposed 
to bear cleistogamous flowers only. It was therefore named S. cleistogama de Bary 
et Paul, and was regarded by Ascherson (Bot. Ztg., xxix, 1871) as an example of 
a plant propagating continuously by self-fertilization. As a matter of fact, the plant 
bore cleistogamous flowers only during the first five years of its cultivation at Halle, 
but afterwards chasmogamous flowers appeared as well. 
Recently (1883) some cases of the constant occurrence of completely closed, 
but otherwise normally formed flowers have been announced by W. Burck (Ann. 
Jard. bot., Buitenzorg, iv, pp. 17-20). In Myrmecodia echinata Gaud., e.g., the 
flowers are completely closed by fusion of the four corolla-lobes, although there are 
secreting nectaries developed beneath a ring of hairs. The stigmas, which are 
papillose on the outer side, alternate with the anthers, and by growth of the 
corolla the pollen of these anthers is brought into contact with the stigmatic 
