OBSERVABLE PROPERTIES OF EACH SPECIES 15 



and botanical systematic literature. Although it is often rather 

 difficult to discriminate between plasticity and complexity with- 

 out having recourse to experiment (see § 17, Remark), we must 

 always bear in mind the fundamental difference between these 

 two kinds of variation. 



REMARK I. : The term variety is used with different 

 meanings and has therefore no longer any exact significance. 

 Certain authors have given a definition of it which they seem 

 soon to have forgotten, since they use the term with various 

 meanings, quite different from their own definition. In the 

 floras and the faunas the term variety is often used as a 

 S5mon5m[a of subspecies, but unfortimately certain forms 

 (variants) which depend on plasticity are also called varieties. 



REMARK II. : I use the term subspecies in the sense of 

 elementary species or petite espece, because it is shorter and 

 clearer than the latter expressions. I call variant any form of 

 a species or subspecies which is brought about by plasticity. 

 Variants are not to be designated by Latin names. (Examples 

 of variants are given in §§ 12, 15, 16, 17.) 



REMARK III. : A species which includes only one sub- 

 species may be called a monotypic species, whereas a complex 

 species includes two or several subspecies. 



§ 19.— PURE LINES.— It is very probable that many sub- 

 species (and monotypic species) consist of two or more pure 

 lines (JOHANSEN), separated from one another by quaUtative 

 chemical differences of their hving mixture which are slighter 

 than those which exist between subspecies (§ 8a), each pure hne 

 being plastic. In the present state of science the discovery of 

 pure lines is only possible by means of delicate experiments. 

 As weU-estabhshed facts are up to now not numerous, our 

 knowledge of this very interesting subject is stiU slight. There- 

 fore I hmit myself to this brief mention of pure lines. 



§ 20.— BUD-VARIATION.— It has often been observed 

 that in a bud of a given plant a certain change takes place the 

 nature of which is hitherto unknown, but the consequences of 

 which are visible : the new parts (branches, leaves, flowers, etc.) 

 produced by the modified bud react in a new way and exhibit 

 properties (characters) by which they differ from the original 

 plant. This peculiar form of variation is called bud-variation. 



Nvmaerous examples of bud-variation have been mentioned 

 by several authors, among whom DARWIN must be cited in 

 the first place.^ 



In many cases the new parts produced by a bud-variation 



^CHARLES DARWIN, The Variation of Animals and Plants under 

 Domestication (second edition, 1875), vol. i. 



