THE PRINCIPLES OF CLASSIFICATION. 317 



cisely similar grounds, carry the analysis a step farther, and 

 regard each phytomer (16) as the individual. Finally, some, in 

 view of their potentially independent life, take the cells, or units 

 of anatomical structure, to be the true individuals ; and this 

 with sufficient reason as regards the simplest cryptogamous 

 plants. Upon the view here adopted, that plants do not rise 

 high enough in the scale of being to reach true individuality, 

 the question is not whether it is the cell, the phytomer, the shoot, 

 the tree, or the whole vegetative product of a seed which answers 

 to the animal individual, but only which is most analogous to it. 

 In our view, its analogue is the cell in the lowest grades of vege- 

 table life, the phytomer in the higher. 1 But, in botanical de- 

 scription and classification, by the individual is meant the herb, 

 shrub, or tree, unless otherwise specified . 



625. Species in biological natural histoiy is a chain or series 

 of organisms of which the links or component individuals are 

 parent and offspring. Objectively, a species is the totality oi.- 

 beings which have come from one stock, in virtue of that moU 

 general fact that likeness is transmitted from parent to progeny. 

 Among the many clelinitions, that of A. L. Jussieu is one of the 

 briefest and best, since it expresses the fundamental conception 

 of a species, i. e. the perennial succession of similar individuals 

 perpetuated by generation. 



626. The two elements of species are : 1 , community of origin ; 

 and, 2, similartty of the component individuals. But the degree 

 of similarity is variable, and the fact of genetic relationship can 

 seldom be established by observation or historical evidence. It 

 is from the likeness that the naturalist ordinarily decides that 

 such and such individuals belong to one species. Still the like- 

 ness is a consequence of the genetic relationship ; so that the 

 latter is the real foundation of species. 



1 For just as successive branches are repetitions and progeny of the 

 parent brancli or stem, the phytomers of the branch are repetitions and 

 progeny each of the preceding one, so forming a series of vegetative 

 generations ; and the whole tree might almost as well represent the individ- 

 ual as one of its branches. The phytomer, as well as the branch, is capable 

 of completing itself by producing roots, but is itself indivisible except by 

 mutilation. Least tenable of all is the conception that the whole product 

 of a seed may be taken to represent the vegetable individual. For then 

 individuals increased by buds and division are wholly unlimited both in ex- 

 tent and in duration, so far as observation can show, and a multitudinous 

 race, not only of the present and past, but perhaps in perpetuity, may con- 

 sist of a single individual. There are, indeed, theoretical reasons for infer- 

 ring that a bud-propagated race may not last so long as a seed-propagated 

 species ; but there is no proof of it. See Darwiniana, Art. xii. 



