THE PATH OF DEGENERATION IN PLANTS 203 



prothallns ; later on in a few Gymnosperms it 

 undergoes a few divisions representing the forma- 

 tion of the antheridium. In Angiosperms the 

 reduction has proceeded further, and each pollen 

 grain besides the prothallus cell produces only one 

 or at most two reproductive nuclei. In all 

 Phanerogams the reproductive nucleus reaches the 

 ovum by being carried in a long tube which grows 

 out from the pollen grain at the expense of 

 nutriment derived from the female tissues. 



Thus, the prothallus may be traced through 

 marked stages of reduction from the condition in 

 ferns, through Selaginella to Gymnosperms and 

 higher flowering plants. But these phases of 

 reduction are by no means to be regarded as 

 repetitions of ancestral conditions. 



In conclusion, it is plain that we cannot assert 

 as a general law, that degeneration retraces the 

 steps of evolution. In the vegetable kingdom no 

 facts support such a conclusion. In certain special 

 cases in the animal kingdom, the most recently 

 developed structures are the first to disappear when 

 atrophy sets in, but this proves no more than that 

 these particular structures happened to be less 

 stable, and to offer less resistance. It is quite 

 impossible to make such facts support the generally 

 held view, that degeneration is a kind of inverse of 

 evolution. 



It is very seldom that a living apparatus with 

 complex functions loses all of them, but usually 



