CHAPTER I 



THE NATURE OF ALTERNATION OF 

 GENERATIONS 



THOUGH this term was in use among morphologists prior 

 to 1860, its interpretation was altogether different from 

 that which is at present in vogue. Introduced by Steen- 

 strup as long ago as 1845, it only carried the idea of a 

 succession of vegetative shoots culminating in the produc- 

 tion of the flower. Though it was discussed at some length 

 by other writers, during the next decade, no material 

 expansion of the idea took place. 



The exhaustive researches of Hofmeister, published in 

 1851 and 1862, placed the study of morphology upon a new 

 plane. In them for the first time a unity of plan was 

 shown to run through all the archegoniate plants, and the 

 old distinction between Cryptogams and Phanerogams based 

 upon the methods of reproduction had to be abandoned, 

 though the full realization of all that his discoveries involved 

 was only slow. In his treatment of the Mosses and Liver- 

 worts, the Vascular Cryptogams and the Gymnosperms, 

 Hofmeister showed clearly the two forms or phases of 

 which their life-cycle consists, and distinguished between 

 a spore-bearing generation and another which exhibits 

 sexual reproduction. The Thallophytes, however, were 

 not included in his scheme. 



Though Hofmeister, with his unequalled skill and patience, 

 established the facts of structure and life-history, he left 

 it to later writers to discuss their bearing, and to formulate 

 what came to be known as the law of alternation of genera- 

 tions. 



