May r.H)0.] BOTANICAL SOCIETY OF EUINIiUKGH oOo 



we meet with a parasitic structure of transitory character 

 — a fruit — an organ in a kind of fashion of the garaeto- 

 phyte, on the other side " the organ " is represented by 

 an independent organism of considerable permanence, and 

 from being the secondary has now become the primary 

 member in the life cycle. 



l>y whatever stages the sporophyte has advanced from 

 parasitism to independence, the progress has resulted in 

 a very marked increase in the structural complexity and 

 physiological importance of the vegetative organs of the 

 sporophyte. 



The physiological importance of its vegetative organs is 

 further emphasised by those cases where, owing to internal 

 or external causes, spore production is long deferred, or 

 inhibited, and the plant is dependent for reproduction 

 on the vegetative multiplication of the sporophyte. 



The slight acceleration in the rate of development of 

 vegetative over sporogenous organs indicated in the Bryo- 

 phyks becomes exaggerated in the Vascular Cryptogams 

 and higher forms, as might be expected from the very 

 marked increase in complexity of structure and functional 

 importance, into a great " time displacement," inasmucli 

 as the vegetative system may be developed for many 

 years before there is any trace of the appearance of 

 the sporogenous organs. 



Traced upwards to the higher flowering plants, the 

 importance of the sporophyte as a whole, and of its 

 vegetative organs in particular, is found to increase, so 

 that ultimately the relative positions of the generations 

 are reversed. The pendulum has swung to the other 

 side, and while at the lower end of the series the 

 sporophyte was parasitic on the gametophyte, and 

 consisted merely of a mass of sporogenous with no 

 vegetative tissue, at the upper end the gametophyte 

 is parasitic on the sporophyte, and its vegetative tissue 

 is reduced almost to the vanishing-point. 



Thus, in contrast to the marked acceleration in the 

 rate of development of the vegetative organs of the 

 sporophyte in correlation with their increased functional 

 and structural importance, we find in the gametophyte a 

 " time displacement " due to retardation of the development 



