260 HISTORY OF BOTANY 



extinct Cycadales. In the same manner the Liliiflorae and 

 all the other syncarpous Monocotyledons have been 

 derived by union of the carpels, by reduction in the 

 number of parts, by epigynous insertion of the perianth, 

 and by other changes in the structure of the flower and 

 fruit, from the polycarpous Monocotyledons (Helobiae), 

 which latter group originated immediately from the 

 polycarpous Dicotyledons (Polycarpicae and Ranales). 

 In the Dicotyledons the Apetalae and Sympetalae are 

 unnatural groups of polyphyletic origin/' 



As Hallier rightly points out in the article from which 

 I have just quoted, " there can exist only one really 

 natural system, namely, that which is identical with the 

 tree of descent ; to reconstruct this, systematic botany 

 should be founded on a much broader and more universal 

 base than at present, comprehending not only the mor- 

 phology of the reproductive organs, but also all the 

 other branches of botany, such as the comparative 

 morphology of the vegetative organs ; comparative 

 anatomy, ontogeny and embryology ; phyto-chemistry ; 

 physiology and ecology ; structure of pollen and seed 

 coat ; relations to climate, seasons and to the surrounding 

 organic world ; plant geography ; palaeophytology, etc." 

 But this is the labour not of one man but of an army ; 

 the task not of one lifetime but of several generations of 

 men. Then, but not till then, may we hope to see in 

 its entirety a genealogical tree of the plant world spread 

 out before us, with reasonable grounds for the belief that 

 it represents, with some degree of accuracy, the succession 

 and lines of descent of plant forms in past ages of the 

 earth's history. 



