2i6o 



A TEXTBOOK OF THEORETICAL BOTANY 



logical plan. The physiological character of an organ was disregarded 

 as of no importance from the morphological point of view. 



De Candolle was influenced by an erroneous view of the processes of 

 stem growth and the two main divisions of his Vasculares were accordingly 

 named Exogenae and Endogenae respectively, the former including the 

 present-day Dicotyledons and Gymnosperms and the latter the Mono- 

 cotyledons, the stems of which were supposed to increase from within 

 outwards. He also unfortunately included with them the Vascular Crypto- 

 gams, a mistake which soon rendered his system obsolete. In the Dicotyle- 

 dons, however, his subdivisions, Thalamiflorae, Calyciflorae and Corolli- 

 florae, survived up to quite recent times. His ideas were further elaborated 

 and to some extent improved by John Lindley (Vol. I, p. 43), who, in 1830, 

 published his " Introduction to the Natural Orders of Plants". In the 

 " Vegetable Kingdom", published in 1846, the Phanerogams were divided 

 into five classes: ) 



1. Rhizogens — Fructifications springing from a thallus. This included 



parasitic and non-chlorophyllous plants. 



2. Endogens — Monocotyledons with parallel-veined leaves. 



3. Dictyogens — Monocotyledons with net-veined leaves. 



4. Gymnogens — Seeds naked (Gymnosperms). 



5. Exogens — Dicotyledons with seeds enclosed in seed vessels. 



Since Lindley's time two great systems of classification have been pro- 

 duced which have commanded world-wide attention. The first is embodied 



in the " Genera Plantarum " by Ben- 

 tham (Vol. I, p. 44) and Hooker, 

 published between 1862 and 1883, 

 which elaborated the De Candolle system 

 as applied to the Angiosperms and 

 Gymnosperms and received at once 

 very general acceptance in this country 

 and subsequently in America. The 

 second is the " Natiirliche Pflanzen- 

 familien " by Engler (Fig. 2067) and 

 Prantl, which appeared between 1887 

 and 1909, and a second edition of which 

 was in process of publication at the 

 beginning of the Second World War in 

 1939. The Engler system soon attracted 

 attention in America and was to some 

 extent accepted by British botanists. 

 Engler's system was derived essentially 

 from that of A. W. Eichler, which was 

 published in 1883. The system adopted 

 by R. von Wettstein in his valuable " Handbuch der systematischen 

 Botanik ", 1901, follows similar lines to that of Engler, as far as the 



Fig. 2067. — Adolf Engler. 



