FLORAL MECHANISM, \ ETC. 
99 
Lamium amplexicaule , Salvia verbenaca , many Leguminosae 
and others. They are usually produced either on shaded 
parts of the plants, or in the colder and darker seasons of 
the year. Vochting 1 has shown that in plants that normally 
produce both open and cleistogamic flowers a reduction of 
the amount of light results in the production of the latter 
kind only. Other observers have shown that temperature 
and other conditions (those in general which reduce nutrition) 
are determining factors also. Though these are determining 
factors, and their effect in any plant is to check the formation 
of open flowers, cleistogamy is not a phenomenon to be put 
on the same level with gynodioecism, for it is hereditary, as 
well as advantageous to the plant possessing it, and cannot 
be artificially produced in plants not showing a tendency to- 
wards it. In chick-weed ( Stellaria inedia) the winter flowers 
tend to cleistogamy, and in water-plants the flowers when 
submerged are often pollinated in the bud. In Myrmecodia, 
&c. only cleistogamic flowers are produced. These show by 
various characters that they have been derived, comparatively 
recently, from open flowers, and may be compared with 
the reduced autogamous flowers of such plants as Senecio 
vulgaris , &c. 
Many of the regularly self-pollinating flowers, such as 
Senecio vulgaris , Capsella, &c., have a very wide distribution. 
This is explained by Wallace by the supposition that small 
changes of climate, &c. react upon the organism in the same 
way as cross-fertilisation, increasing its fertility, strength of 
constitution, variability and so on. The wide distribution of 
many cross-pollinated flowers is prevented by the circum- 
stances of insect distribution. Many wind-pollinated flowers, 
however, are widely distributed. 
Zoophily, or pollination by animals other than insects, 
seems to occur in a number of plants ; e.g. the flowers of 
Alocasia, Rohdea, &c. are “ snail-flowers ” ( malacophilous ) ; 
those of Freycinetia “ bat-flowers ” ; those of Marcgraviaceae, 
Erythrina, Salvia splendens , Passiflora sp. , Abutilon sp. and 
many more in the tropics of America are “ humming-bird 
flowers 5 ’ ( ornithophilous ). Most of the last-named are bright 
1 Vochting, U. d. Einfi. d. Lichtes a. d. Gest...d. Bliiten , Prings. 
Jahrb. f. wiss. Bot. 1893; Willis in Linn. Soc. Journ. xxx. 1893, p. 295, 
and Sci. Progr. Nov. 1895. 
