116 



TAXONOMY. 



is a multitude of families in which the stipulae are a constant 

 appendage of vegetation ; for example, the Rubiaceae, Mal- 

 vaceae, Leguminosae, Arnentaceae ; whilst spines may be pre- 

 sent or wanting in a great many families, without making any 

 perceptible difference ; for instance, in the Rosaceae, Legu- 

 minosae, and so forth. In the same manner, the constant 

 absence of an organ, in certain famihes, is of more moment 

 than its accidental appearance, when it is wanting in other 

 related forms. Thus the Grasses, so far as we know, have 

 never nectaries, as they also never have compound leaves, 



II. On the Means which Nature affords for enabling us to 

 know OrgmiSy and thereby to avoid mistakes.. 



174\ 



In all inquiries into the history of plants, it is an object of 

 the highest importance that we should have a correct idea 

 respecting the purport and nature of any organ, because then 

 only can we flatter ourselves with the idea of having obtained 

 a proper insight into the economy of plants. This department 

 of the study has made remarkable progress in our days, since 

 men began to free themselves from the fetters of the schools, 

 and from the prejudices of authority. The great Founder of 

 Scientific Botany frequently mistook the nature of organs, es- 

 pecially when he saw nectaries, where none are and never can 

 be. Audit is not long since it was believed, that in the Ferns 

 there were anthers in very various organs, which, however, 

 have a very different purpose. 



The first thing that we have to do, in order to become ac- 

 quainted with the nature of an organ, is to endeavour to find 

 out whether it really performs the functions, to which, by its 

 form, it seems to be destined. 



Even when the form varies, we must be determined by the 

 function to assign to the organ a definite nature. It is well 

 known how different is the form of nectaries, and how great 

 a variety takes place in the structure of filaments. If, how- 

 ever, the function be really the same, we must explain their 

 nature upon a common principle. But he who permits himself 



