30 PRINCIPLES OF PLANT-TJiBATOLOGY. 



the process of reduction, in the guise of an advanced 

 type of simplification, has played in the course of the 

 evolution of modern vascular plants. 



If we cull a particular instance from our knowledge 

 of the configuration and. habit of the seed-ferns of the 

 Carboniferous epoch and the method by which they, 

 through the process of reduction and simplification, 

 from an excessive complexity of their reproductive 

 apparatus, gave rise to that of the Cycads of the 

 Mesozoic period ; and if we consider how greatly the 

 cone of these Mesozoic Cycads resembles in general 

 conformation the "flower" of an Angiosperm; we 

 shall feel that a " flower " is, after all, merely the final 

 stage in the evolutionary transformation of a leafy 

 shoot of complex organization such as we find in the 

 Pteridosperms. A sepal, a stamen, and a carpel have 

 probably each been derived during the course of evolu- 

 tion from a large foliar organ, whether green and 

 assimilating or not, of complex structure. The recep- 

 tacle or floral axis has likewise in the course of ages 

 been excessively abbreviated owing to complete or 

 almost complete extinction of the internodes between 

 the various floral leaves. All these changes have 

 resulted in the characteristic modern structure which 

 we term a " flower," e. g. the tulip. 



When, as under the stimulus of excessive nourish- 

 ment, the normal balance of the structure is upset, 

 which condition is a kind of disease, there appears to 

 be a tendency for it to revert to a state which can 

 only be termed ancestral, but ancestral merely in the 

 sense that two changes take place, namely, an exces- 

 sive elongation of the axis in which the internodes 

 develop, and secondly, the modification of the various 

 floral leaves into foliage-leaves. The flower, in other 

 words, frees itself from the bonds of contraction and 

 condensation in which it has so long been held, and 

 attains to a reminiscence of bygone ages in which its 

 ancestors revelled in the luxuriance of a more extended 

 scope of shoot and leaf. A reversion, be it noted, only 



