148 Development of the Natural System under [BOOK i. 



Rhizogens is much overrated on account of their striking 

 habit the Monocotyledons are separated into two classes on 

 the strength of an unimportant mark. The characters assigned 

 to all these groups are on the whole thoroughly faulty. 



These systems have been selected for notice from among 

 many others, because they attained an extended notoriety and 

 importance from the circumstance that their authors, Brong- 

 niart excepted, made them the occasions of comprehensive 

 descriptions of the whole vegetable kingdom, and again be- 

 cause it would be superfluous for our present purpose to 

 bestow a closer consideration on the systems of less eminent 

 men. Whoever desires further information on the matter will 

 find it in the introduction to Lindley's ' Vegetable Kingdom ' 

 of 1853. 



If we consider the principles and points of view adopted 

 in these systems, one thing especially strikes us, that, except 

 in the case of Bartling, physiologico-anatomical marks were 

 employed along with morphological ones to characterise the 

 primary divisions ; their authors fell into the mistake committed 

 by De Candolle, and unfortunately these very marks rested in 

 part or wholly on misapprehensions, as in Endlicher's division 

 into Acrobrya, etc., and Lindley's classes of Rhizogens and 

 Dictyogens. It was still more unfortunate that individual sys- 

 tematists obstinately refused to accept well authenticated facts, 

 which it is true had not been discovered by systematists, but 

 were nevertheless of the highest value for the system. It is 

 scarcely credible that Lindley in 1845, and again in 1853, 

 maintained the distinction between endogenous and exogenous 

 growth in stems, though Hugo von Mohl had in 1831 produced 

 decisive proof that this distinction laid down by Desfontaines 

 and adopted by De Candolle had no real existence. The 

 same was the case with the characters of the Cryptogams, in 

 which the mark of having no sexual organs was repeatedly 

 adopted as running through the whole class, although various 

 instances of sexuality in Cryptogams were known before 1845 ; 



