No. 496] ASPECTS OF THE SPECIES QUESTION 231 



forms vary according to the situation of the plant and 

 during reproduction, we can not regard these - forms by 

 any means as distinct species, but we must view them as 

 corruptions. 



We see, that, in order to decide respecting the idea of 

 a species, an observation of many years, and of much 

 accuracy, is often required; and that the cultivation of 

 plants, from the most different climates, in botanical 

 gardens, is in the highest degree necessary for their dis- 

 crimination. 



Prom Lindley, John, An Introduction to Botany, Lon- 

 don, 1832. 



A species is a union of individuals agreeing with each 

 other in all essential characters of vegetation and fructi- 

 fication, capable of reproduction by seed without change, 

 breeding freely together, and producing perfect seed 

 from which a fertile j)rogeny can be reared. Such are 

 the true limits of a species; and if it were possible to 

 try all plants by such a test, there would be no difficulty 

 in fixing them, and determining what is species and what 

 is variety. But, unfortunately, such is not the case. 

 The manner in which individuals agree in their external 

 characters is the only guide which can be followed in the 

 greater part of plants. We do not often possess the 

 means of ascertaining what the effect of sowing their 

 seed or mixing the pollen of individuals would be; and, 

 consequently, this test, which is the only sure one, is, in 

 practice, seldom capable of being applied. The deter- 

 mination of what is a species, and what a variety, be- 

 comes therefore wholly dependent upon external char- 

 acters, the power of duly appreciating which, as indic- 

 ative of specific difference, is only to be obtained by ex- 

 perience, and is, in all cases, to a certain degree arbitrary. 

 It is probable that, in the beginning, species only were 

 formed ; and that they have, since the creation, sported 

 into varieties, by which the limits of the species them- 

 selves have now become greatly confounded. For ex- 



