602 THE SUBDIVISIONS OF THE VEGETABLE KINGDOM. 



as the highest aim of botanical endeavour. He never completed a natural system, 

 leaving only a fragment (published 1738). 



The credit of actually founding a natural system of plants is usually attributed 

 to Bernard de Jussieu (1699-1777) and his nephew Antoine Laurent de Jussieu 

 (1748-1836). For many years this system only found expression in the laying 

 out of the beds in the Botanic Garden of Trianon (at Versailles); it first became 

 generally known some thirty years after its inception, when the younger de 

 Jussieu published his Genera Plantarum (1789). A hundred families of plants 

 are distinguished and grouped under fifteen classes, which, in their turn, fall 

 under three main co-ordinated divisions (Acotyledones, Monocotyledones, Dicoty- 

 ledones). The three main divisions^ are founded upon the structure of the 

 embryo at germination. In the Acotyledones the embryo consists of but a 

 single cell and is destitute of cotyledons, in the Monocotyledones it is multicellular 

 and provided with one cotyledon, whilst in Dicotyledones there are two cotyledons. 

 The Acotyledones are equivalent to the Cryptogamia of Linnaeus (his 24th class, 

 cf. p. 290) and constitute the 1st class of the new system. The Monocotyledones 

 fall into three classes according to the relative position of the stamens to the 

 ovary (Monohypogynse, Monoperigynse, MonoepigynsB). The Dicotyledones are 

 first subdivided into three groups according to the structure of the perianth, 

 viz., into those destitute of petals (Apetalse); those with distinct calyx and corolla, 

 the petals being united (Monopetalse) ; and those also having calyx and corolla, 

 with all the petals free from one another (Polypetalse). Each of these groups is 

 subdivided into three classes, based on the relative position of stamens to ovary 

 (in the case of the Monopetalse of corolla to ovary). Since in the Dicotyledones 

 with unisexual flowers it was impossible to indicate the relative position of 

 stamens and ovaries, a special class (Diclines irreguläres) was set aside for them. 

 The institution of this last class does not mark an advance towards a natural 

 system; whilst the limitations of the other classes in respect of the relative positions 

 of stamens to ovary is cumbrous and unnatural, still they are less artificial than 

 those of the Linnean Sexual System. The distinctive features of the system of 

 de Jussieu are the broad characters upon which the families are based — the whole 

 structure of the plant being taken into consideration^ — and especially the recogni- 

 tion of Monocotyledons and Dicotyledons as equivalent groups of Flowering 



1 A. L. DE JUSSIEU'S SYSTEM OP 1789. 



Class. 



Acotyledones I. 



( Stamina hypogy na II. 



Monocotyledones -[ perigyna III. 



I. epigy na IV. 



/ f Stamina epigyna V. 



Apetalse - perigyna VI. 



I hypogyna VII. 



( Corolla hypogyna VIII. 



,.. , , , /Monopetate - perigyna. IX. 



Dicotyledones { '■ I . ( Antheris connatis X. 



] I ^P'^y'^'^ 1 distinctis XL 



f Stamina epigyna XII. 



Polypetalae - hypogyna XIII. 



t perigyna XIV. 



i^Dicliaes irreguläres XV. 



