CHAPTER III. 



ON THE BALANCE OF THE ALTERNATING GENERATIONS 

 OF ARCHEGONIATAE. 



HOFMEISTER'S great work on the Higher Cryptogamia, alluded to in the 

 previous chapter, was not a mere description of observations, but a com- 

 parative treatise. It not only revealed the life-stories of the various types 

 of plant-organisation which he examined, but in it he also showed that 

 their several stages corresponded in essential features. Notwithstanding 

 wide differences of detailed form and of proportion, it was demonstrated 

 that, as regards position among the recurrent events of each life-cycle, 

 the neutral generation, or sporophyte, and the sexual generation, or 

 gametophyte, remained distinct and recognisable in such diverse plants as 

 the Bryophytes, Pteridophytes, and Gymnosperms. In arriving at this 

 conclusion it was Hofmeister's great merit that he kept his eye securely 

 upon those critical points where the individual life is represented by a 

 single cell, viz. the zygote, and the spore. However differing in size or 

 in complexity, he held as comparable, or, as it is said, ''homologous," the 

 phases which intervened respectively between those two events. This great 

 generalisation of Hofmeister, stated by him with a brevity and a simplicity 

 of language as remarkable as its content was new and far-reaching, has 

 formed the essential foundation of all subsequent morphology of Archegoniate 

 Plants. A series of examples will now be quoted in illustration of it, and 

 these will be selected to show the differences in form and in the relative 

 proportions of the two generations ; but it will not be necessary to enter 

 into a continuous account of the life of each example, for with certain 

 modifications the essentials of sexuality and of spore-production remain 

 the same in them all. 



In Riccia, one of the simplest of the Liverworts, the gametophyte, or Ricria- 

 plant, as~Tt is called on account of its being more prominent than the 

 sporophyte, is a green, dichotomously branched thallus, showing localised 

 apical growth, while it is thick in proportion to its area : some species float 

 on water, others are attached by rhizoids to the substratum of soil. The 



c 



