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SEVENTH SUBDIVISION. 

 PROTOPHYTA. 



Whether the Protophyta should be reckoned as a distinct subdivision 

 from the Algae, or only as the lowest members of that great series, is a 

 question rather of convenience than of principle. In an ideal system of 

 classification founded exclusively on genetic affinities, those organisms 

 would be regarded as ' protophytes ' which were the earliest heralds of 

 the appearance of vegetable life on- the surface of the globe. But, from 

 the structure and conditions of life of such organisms, it is impossible that 

 they can have been preserved to us in the fossil state, and it is only from 

 the comparative simplicity or complexity in the structure of an organism 

 that we can conjecture whether it is an archaic or a derivative form. And 

 here, as was remarked in the Introduction, we are extremely liable to be 

 misled if we neglect to take into account the phenomenon of the constant 

 appearance of degeneration or retrogression in the vegetable kingdom. 

 An organism may be simple in its structure either because it has never 

 risen, through countless ages, above the simplicity of its primeval ances- 

 tors, or because it has fallen back from a more complicated condition. 

 The object of the scientific systematist should be to separate, so far as 

 possible, between these two sets of organisms, to include the former 

 among his lowest class of protophytes, and to relegate the latter in each 

 case to the class from which they have degenerated. But this task is 

 attended with great difficulties, and is often well-nigh impossible. An 

 organism may display degeneration of one set of organs, while another 

 set manifest no such degeneration and have even continued to develop. 

 We may take it indeed as a general law that wherever you have either 

 the vegetative or the reproductive organs strongly developed, while the 

 •other set are very feeble or altogether wanting, you have prima facie 

 evidence of retrogression. But, on the other hand, degeneration may 

 take effect in all the organs of a plant, leading to retrogression in all lines 

 towards, it may be, the archaic form. As knowledge advances, the constant 

 tendency will be to transfer to this class of retrogressive members of 

 higher families forms previously regarded as protophytal. 



