PEELIMINAEY DISCOURSES; 



5. P segregata, where each floret in th&- head 1 has a kind of 



involucre of its own separating it from the others. 



The Orders of the Cryptogamia, or 24th Linnaaan Class, have 

 been already noticed, as being necessarily natural.. By distributing 

 the Genera, which LINNAEUS placed in Dodecandria, Polyadelphia,. 

 and Polygamia, among the other Classes, the number of those pri- 

 mary divisions may be reduced to 21, withoujt any detriment to the 

 System. The simplicity and elegance of this method the facility 

 with which it is learnt, and applied are considerations which have 

 made it extensively popular, especially with young Botanists: 

 and although it is avowedly artificial',, the fact of its bringing so 

 many genera into natural groups, is strong evidence that it is based 

 on the most important organs in the vegetable economy.* 



I shall now conclude these desultory Discourses, by an attempt 

 briefly to indicate the mode in which Plants are classified, and 

 viewed, under the Natural System. The object proposed by that 

 System, is "to bring together into groups those plants which most 

 nearly resemble each other, not in a single and perhaps unimportant 

 point (as in an artificial classification), but in all essential particu- 

 lars ; f and to combine the subordinate groups into larger natural 

 assemblages, and these into still more comprehensive divisions, so 

 as to embrace the whole vegetable kingdom in a methodical arrange- 

 ment. All the characters which plants present, that is, all the 

 points of agreement or difference, are employed in their classifica- 

 tion ; those which are common to the greatest number of plants 

 being used for the primary grand divisions;, those less comprehen- 

 eive for subordinate groups, &c. ; so that the character, or descrip- 

 tion of each group, when fully given, actually expresses all the 

 known particulars in which the plants it embraces agree among 

 themselves, and differ from other groups of the same rank. This 



* The most superficial observer cannot fail to be struck with the fact, that the 

 Sexual System groups together with comparatively few exceptions the genera 

 belonging to the following eminently natural and some of them eminently 

 large families of flowering plants : namely. Cruciferae, Malvaceae, Leguminosae, 

 Hosaceae, UmbeHiferae, Compos itae, Labiatae,Boraginaceae, Orchidaceae, Cyperaceae, 

 and Gramineae, not to mention a number of others, wh ich will occur to the 

 experienced Botanist, as more or less approximating a natural association. 



{The Njtiurallt's&ys Prof. DE CxyooLLE arranges or groups together all those 

 beings which have the greatest number of organs in common, or of similar struc- 

 ture, and separates those which possess but a small number of them in common : 

 whence it results that, while the perfection of an Artificial System consists in 

 connecting with the character of the Classes the smallest possible number of 

 ideas, a Natural Method, on the contrary, is so much the more perfect, as thu 

 characters of the Classes are expressive of a greater number of ideas, 



UNIVERSITY 



