INTROnUCTION. ix 



and discuss its value with that of the characters on whicli are based 

 the series into which the whole group is divided. Finally, the 

 properties of tlie useful plants it contains are enumerated. After 

 the text comes a Genera, in which, omitting the characters common 

 to the whole series and defined in the first type described, only 

 the important points which mark off" each genus sharply from its 

 neighbours are given. These generic descriptions will of course 

 be more detailed in those very natural orders which were formerly 

 considered as great single genera, or as collections of a few very 

 large genera. In such cases it will be unnecessary to lay any 

 stress on minute shades of distinction in the text ; we shall thus 

 avoid useless repetitions in certain groups made up of nearly 

 similar elements, such as Leguminosm, Crucifera, Compositce, Graminea, 

 and the like. 



As with the text so with the figures. The genera whose organi- 

 zation is either most important or least known, and especially 

 those which head our series, will have most of their parts figured : 

 habit, inflorescence, flower (entire and in longitudinal section), sexual 

 organs, floral diagram, fruit, seed (entire and in section), &c. But 

 of the genera derived from these only the chief differentiating cha- 

 racters will be figured, while there will be no need to draw those of their 

 organs which are similar to the same organs in the typical genus. 



The reasons for the succession in which the diff'erent families will 

 be described it appears illogical to consider here, or to discuss the 

 classification of objects before we have studied them, and while their 

 exact characters are supposed to be still unknown. As, with each 

 order, until we have analyzed and described its genera and compared 

 them with one another, we are unable to decide on the value of 

 the characters which allow us to arrange them in series ; so, only 

 after scrutinizing the organization of the whole of the Vegetable 

 Kingdom, shall we be in a position reasonably to inquire into the 

 principles which may govern its classification. What profit, indeed, 

 can result from discussing the value of fiicts and characters that 

 we have as yet not investigated ? 



Suffice it, then, at the commencement of this work, to say merely 

 that in the first instance we shall follow the generally received 



