344 GENERAL CONCLUSIONS. CHAP. MIL 



render it strictly cleistogamic. The various organs 

 would also, it is probable, be modified by the peculiar 

 conditions to which they are subjected within a com- 

 pletely closed flower ; also by the principle of corre- 

 lated growth, and by the tendency in all reduced 

 organs finally to disappear. The result would be the 

 production of cleistogamic flowers such as we now 

 see them; and these are admirably fitted to yield a 

 copious supply of seed at a wonderfully small cost to 

 the plant. 



I will now sum up very briefly the chief conclusions 

 which seem to follow from the observations given in 

 this volume. Cleistogamic flowers afford, as just 

 stated, an abundant supply of seeds with little ex- 

 penditure ; and we can - hardly doubt that they have 

 had their structure modified and degraded for this 

 special purpose ; perfect flowers being still almost al- 

 ways produced so as to allow of occasional cross-fertilisa- 

 tion. Hermaphrodite plants have often been rendered 

 monoecious, dioecious or polygamous ; but as the sepa- 

 ration of the sexes would have been injurious, had not 

 pollen been already transported habitually by in- 

 sects or by the wind from flower to flower, we may 

 assume that the process of separation did not com- 

 mence and was not completed for the sake of the 

 advantages to be gained from cross-fertilisation. The 

 sole motive for the separation of the sexes which 

 occurs to me, is that the production of a great number 

 of seeds might become superfluous to a plant under 

 changed conditions of life ; and it might then be highly 

 beneficial to it that the same flower or the same indi- 

 vidual should not have its vital powers taxed, under 

 the struggle for life to which all organisms are sub- 

 jected, by producing both pollen and seeds. With 



