Polygala polygama and P. paucifiora. I4I 
existence of the species in case sexual reproduction, depend- 
ing on favorable outward conditions, failed. 
Darwin,’ quoting Delpino, regards his view to a certain 
extent as correct. He points out that a majority of plants 
which produce cleistogamic flowers, have their evident ones 
adapted for fertilization by insects, and that during certain sea- 
sons, through scarcity of insects, these would fail to be fer- 
tilized, and so there would be a failure of seed production, 
unless this were accomplished by some other means. “It 
is difficult to avoid the belief that the production of cleis- 
togamic flowers, which ensured under all circumstances a full 
supply of seed, has been in part determined by the perfect 
flowers being liable to fail of their fertilization.”” But he imme- 
diately makes it clear that he does not consider that this is the 
chief reason for the development of cleistogamic flowers. He 
points out that wind-fertilized genera also produce such, and 
says further of the causes of cleistogamy: ‘ The production 
of a large supply of seeds with little consumption of nutrient 
matter and expenditure of vital force, is probably a far more 
efficient motive power. The whole flower is much reduced in 
size; but what is more important, an extremely small quan- 
tity of pollen has to be formed, as none is lost through the 
action of insects or the weather, and pollen contains much 
nitrogen and phosphorus.” And seeing that they possess 
this advantage, he thinks that if any cause prevented a plant 
from completing the development of its flower, natural selec- 
tion would step in to preserve this advantage and so lead to 
the production regularly of cleistogamic flowers. 
Mr. S. Le M. Moore? criticised Darwin’s views on cleisto- 
gamy, basing his opinions on a few observations of Vegetable 
Marrow. He points out that conspicuous flower-parts 
quickly wither after pollination, and suggests that if pollina- 
1 Darwin. Forms of Flowers, p. 339. 
2Trimen. Jour. of Bot., 1881, p. 84. 
