i8o 
THE PLANT WORLD. 
former. Still, in all cases functional pollen-grains and ovules 
are formed. Whatever differences in structure occur between 
cleistogamous and chasmogamous flowers of these species are 
altogether the results of delays in the unfolding of the bud. 
There are recorded in botanical literature large numbers of 
experiments and observations on the influence of nutrition (in 
the wider sense) upon the size and development of plant organs. 
Goebel cites many cases bearing especially on the development 
of the floral organs, to show that arrest of development is in 
general a function of diminished nutrition. From this he con¬ 
cludes that cleistogamy is always a question of nutrition too in¬ 
sufficient in quantity or too poor in quality to produce perfect 
flowers. He cites experiments in which plants normally pro¬ 
ducing cleistogamous flowers either before or after the chas¬ 
mogamous ones, produced under certain conditions only the one 
kind, while under certain other conditions only the other. The 
dependence of cleistogamy upon nutrition may then exist even 
where it appears with seeming regularity at a certain time in 
the course of a plant’s development, as in Impatiens and Viola. 
The teleological explanation of the origin of cleistogamy is 
accordingly not tenable. Cleistogamy bears no causal relation 
either to a lack of pollinating agencies, or to the failure of the 
chasmogamous flowers to produce seeds. It is rather dependent 
upon inadequate nutrition, and upon correlation with vegetative 
organs. 
It is important to distinguish between the external conditions 
which may stimulate changes in the structure of plant organs and 
the purpose which such reactions may serve. The uses which a 
structure may serve are not to be confounded with the causes 
that produce it. Flowers are usually considered less plastic than 
vegetative organs, that is, as being less influenced in their forms 
by external conditions,—and in general they are so: but the sizes 
and number of parts within a flower do depend on the quantity 
and quality of available nutriment. And the same must be true 
of cleistogamy, without regard to the advantage or disadvantage 
this phenomenon may be to the species. 
Even such plants as have absolutely no need of them may pro- 
