8 A History of Botany, 1 860-1 goo 



differentiation of structure must be sought in division of 

 labour. 



Two theories of fundamental importance were still held 

 by most botanists : the one, that of the constancy of 

 species ; the other, that of metamorphosis. Of these, the 

 first was destined to disappear almost at the beginning of the 

 period 1860-1900, which forms the subject of this volume ; 

 the second was to give rise to considerable discussion and 

 to obtain a presentation from an altogether different 

 point of view. 



These changes and the great development of the science 

 that marked the period under review were in large measure 

 the result of the appearance of two epoch-making works, 

 each of the profoundest importance. It is difficult to 

 compare them, for though they had certain features in 

 common these did not appear upon the surface. The one 

 appealed to botanists in particular, the other to the world 

 in general. They were Hofmeister's researches on the 

 Cryptogams and their affinities, and Darwin's Origin of 

 Species. Appearing as both did just on the threshold of 

 our period, and appealing to the whole biological world, 

 they marked the commencement of the period as a starting 

 point of generalizations, wider and of importance further 

 reaching than any of the great generalizations of the past. 



Hofmeister's illuminating investigations established the 

 recognition of a more or less uniform plan of organization 

 running throughout the whole vegetable kingdom, and 

 overthrew what had till his time been considered to be 

 the fundamental difference between the Cryptogams and 

 the Phanerogams. He showed that, when co-ordinated 

 and arranged, the structures of the reproductive mechan- 

 isms in both groups point to a progressive development 

 or evolution throughout the vegetable kingdom, and 

 that consequently a consistent phylogeny may ultimately 

 be demonstrated connecting all the forms in one great 



