Development of the Natural System under [BOOK 



i. 



dari in vegetabilibus negat generatio continuata, propagatio, 

 observations quotidianae, cotyledones.' 



In spite of all this one important advance was made by the 

 successors of Jussieu ; the larger groups of genera, the families, 

 were defined with the certainty and precision, with which 

 Linnaeus had fixed the boundaries of species and genera, and 

 were supplied with characteristic marks. They succeeded also 

 in clearly distinguishing various still larger groups founded on 

 natural affinity, such as the Monocotyledons and Dicotyledons ; 

 the distinction between Cryptogams and Phanerogams was by 

 degrees better appreciated, though this point could not be 

 finally settled, so long as it was attempted to reduce the Cryp- 

 togams entirely to the scheme of the Phanerogams. The chief 

 hindrance however to the advance of systematic botany, at 

 least at the beginning of this period, lay in the defective mor- 

 phology enshrined in Linnaeus' terminology and in his doctrine 

 of metamorphosis. A great improvement certainly was effected 

 in the early part of the i9th century by De Candolle's doctrine 

 of the symmetry of plants, a doctrine which has been much 

 undervalued, and that merely on account of its name ; it is 

 really a comparative morphology, and the first serious attempt of 

 the kind since the time of Jung that has produced any great 

 results ; a series of the most important morphological truths, 

 with which every botanist is now conversant, were taught for 

 the first time in De Candolle's doctrine of symmetry in 1813. 

 But one thing was wanting not only in Jussieu and De Candolle, 

 but in all the systematists of this period, with the single excep- 

 tion of Robert Brown, and this was the history of development. 

 The history of the morphology and systematic botany of this 

 period shows indeed, that the comparison of mature forms 

 leads to the recognition of many and highly important morpho- 

 logical facts ; but as long as matured organisms only are 

 compared, the morphological consideration of them is always 

 disturbed by the circumstance that the organs to be compared 

 are already adapted to definite physiological functions, and 



