416 



PLAN OF THE NATUEAL SYSTEM. 



sibly into others, so that their limits cannot be accurately defined ; 

 and no perfect system can be constituted until all the plants of the 

 globe are known. Moreover, many artificial means are avowedly 

 used in all natural systems to aid the student. 



The early natural systems were very imperfect, being founded on 

 comparatively vague views of structure and affinity. Such were the 

 systems of Magnol and Adanson. The sketch of a natural system by 

 Linnaeus was very incomplete, apd even that of the celebrated Ray 

 was imperfect. It was not untU the knowledge of structural botany 

 had advanced, that the affinities of plants were ascertained, and the 

 relative importance of the different characters discovered. The na- 

 tural systems of the present day recognise a certain subordination of 

 characters, founded on the fact that some organs are of more import- 

 ance to the life of plants than others. The relative values of these 

 characters are determined by the study of organisation, and are not 

 fixed by arbitrary rules. The following table will illustrate this 

 subordination of character : — 



Subordination in Value of the Organs of the same Class. 



Relative Values. 

 1. 



Elementary. 

 Cellular Tissue. 

 f Vascular Tissue . 

 1 a. Spiral Vessels 

 i 6. Pitted Vessels 

 I c. Scalariform 



iStomata 



Nutritive. 



Emtryo. 



a. Cotyledon. 



6. Radicle. 



li. Plumule. 

 Spore. 

 . (.ProthaUus . . 



■ Eoot, Stem, Leaf, 

 Frond, Thallus 



Reproductive. 



' 1. Stamens and Pistil. 

 I 2. Antheridia and Arche- 

 gonia. 



Fruit. 



Pericarp. 



Theca. 

 ( Perianth. 



4. \ a. Corolla. 



( 6. Calyx. 



( Inflorescence. 



5. i Torus, Nectary. 



( Bract, Involucre. 



_ Thus, cellular tissue occupies the highest place, as being most 

 universally diffused, and capable of carrying on all the functions j next 

 comes vascular tissue. By the consideration of these, the two great 

 divisions of cellular and vascular plants are determined. There is 

 nothing in the nutritive and reproductive systems of the same value 

 as cellular tissue. The embryo and its parts are reckoned as occupy- 

 ing the highest place in the nutritive system, and as corresponding in 

 value with the vascular among the elementary tissues. In the same 



