CHAP, m.] 'the Dogma of Constancy of Species. 149 



Schmidel had described the sexual organs of the Liverworts 

 about the middle of the previous century, Hedwig those of the 

 Mosses in 1782, and Vaucher in 1803 had suggested that the 

 conjugation of Spirogyra among the Algae should be regarded 

 as a sexual act ; the systematists in fact did not know what to 

 make of these intimations. 



It was again a misfortune that the systematists in their 

 labours often neglected to distinguish between the search 

 for marks and the use to be made of them ; the examination 

 of all possible marks should lead to the establishing the sys- 

 tematic importance of certain fixed marks or their value for 

 classification. When research has done its work, then it is 

 sufficient in exhibiting the system to put forward only the 

 prominent marks ; and frequently a single one suffices to 

 unite a natural group. Such a leading mark is like the 

 standard of a regiment ; its significance is not great in itself, 

 but it serves the great practical purpose of indicating a whole 

 group of marks which are connected with it. It was a still 

 greater misfortune that scarcely any systematist after De Can- 

 dolle endeavoured to form a clear conception in his own mind 

 of the principles on which the natural system must be ela- 

 borated, and to set them forth in a connected form as the 

 theory of the system. The student had to accept the arrange- 

 ment offered him as a fact simply without understanding it, 

 and the systematists themselves usually followed only a blind 

 feeling in the framing of their groups, and never unfolded the 

 grounds of their proceeding with logical distinctness. In this 

 respect John Lindley forms an honourable exception, inas- 

 much as he did, on several occasions after 1830, give full 

 expositions of his views on the principles of natural classi- 

 fication, and like De Candolle endeavoured to develop a 

 theory of the system 1 . But he deserves credit only for the 



1 Augnste de Saint-Hilaire was born at Orleans in 1779, and died there 

 in 1853; he was Professor at Paris, and in 1840 published his ' Le9ons de 

 Botanique comprenant principalement la Morphologic Ve"getale,' etc. This 



