Polygala polygama and P. paucifiora. 145 
suggestion in this connection that the developing fruits from 
the minute flowers require a great quantity of carbohydrates 
and so hinder the development of fruit from the evident 
flowers. Knuth! reviews the opinions of several of these 
observers and concludes that light is the important factor in 
cleistogamy. It will be noticed that Darwin's suggestion 
that they were developed as a means of economy, does not 
appear in the modern views. 
Perhaps, therefore, the consensus of opinion at the present 
time in regard to cleistogamic flowers may be fairly stated as 
follows: They are caused primarily by deficiency in light, or 
by other unfavorable conditions, and are to be regarded as 
degenerate or imperfectly developed chasmogamic flowers. 
They are of advantage to a plant in preserving the species 
when ordinary fertilization fails, and in the fact that their 
fruits are often developed underground where they are 
protected. 
These views either as to causes, or the purpose of cleisto- 
gamic flowers are not very satisfactory when applied to such 
aérial ones as are borne by Polygala polygama, In the first 
place these are produced in abundance in the open fields 
under the sun of July and August. The plants which bear 
them show every sign of health, vigor and normal develop- 
ment. If indeed it may have been that lack of light induced 
their development in the first instance, it is necessary to 
assume that there is some other cause at work when we find 
them developed under all circumstances, .and under bright 
sunlight. The view that they are for the purpose of preserv- 
ing the plant when unfavorable circumstances prevent crossing, 
is also more or less unsatisfactory, for each summer the cleisto- 
gamic flowers are produced in great profusion. One would 
hardly suppose that the chasmogamic flowers habitually fail 
to find the conditions to which they are adapted. The fact 
1Knuth. Bliithenbiologie. 
Io 
