96 HISTORY OF BOTANY 



he based it on a principle which he enunciates in the 

 following words : " Physiological characters are of greater 

 importance in regulating the natural classification of 

 plants than structural," thus showing himself diametric- 

 ally opposed to De Candolle, who asserted that a true 

 classification must be founded on morphological features 

 only. He divided plants into Asexual or Flowerless 

 and Sexual or Flowering. The Asexual include Thallogens 

 and Acrogens, while the Sexual embrace five classes : 

 Rhizogens (parasites), Endogens, Dictyogens, Gymnogens, 

 and Exogens. The Rhizogens had nothing in common 

 beyond their parasitism — a physiological characteristic, 

 while the Dictyogens were merely a few orders of Mono- 

 cotyledons, or Endogens, with reticulate veined leaves. 

 The Exogens or Dicotyledons are subdivided into 

 dichnous and hermaphrodite, and the latter again into 

 h3rpogynous, perigynous, and epigynous orders. I do 

 not think it would serve any useful purpose were I to 

 explain to you in further detail any of the systems 

 Lindley put forward from time to time, still less to 

 expose the many errors and inconsistencies found in them. 

 Without actually going so far as to say, with Sachs, that 

 Lindley's final effort at subdividing plants as given in 

 the Vegetable Kingdom was " one of the most unfortunate 

 classifications ever attempted," still the general impression 

 one gets from a study of his pubHcations on taxonomy 

 is that his mind was in constant state of vacillation on 

 the subject, laying down guiding rules which he does not 

 follow or follows only half-heartedly, and abandoning 

 one scheme only to replace it with another and more 

 erroneous one. 



You will remember that A. P. de Candolle had been 

 the leading opponent of Linnaeus's artificial system and 

 had put forward a classification of his own based on or 

 adapted from those of Ray and De Jussieu. His son, 

 Alphonse de Candolle, followed up his father's work and 

 is mainly responsible for the great Prodromus Systematis 



