XVl PBELIMINABY DISCOUBSES. 



3. That in the study of those two kingdoms, we should never 

 lose sight of the essential characters which distinguish them ; and 

 should extend the application of the principles, which are peculiar 

 to each, with great caution, lest we be misled by a false analogy. 



DISCOUKSE III. 

 External organs of Plants, and their successive modifications. 



IN the preceding Discourse, we endeavored to furnish a definition, 

 or distinct idea, of the three great kingdoms in Nature, and, 

 especially, to present a Sketch of the general resemblance, and dis- 

 tinguishing characters, of the two organic kingdoms, from the 

 learned Treatise of Professor DE CANDOLLE. We shall now proceed 

 to notice some of the more remarkable traits, and phenomena, of 

 the vegetable economy. For an illustration of the intimate struc- 

 ture, and physiology of Plants, the Student is referred to the 

 admirable Text-Book of Prof. A. GRAY : Our present purpose being 

 merely to speak of the external organs, or those obvious appen- 

 dages, and features, which give character to the vegetable tribes, 

 and form the basis of classification. 



It is a circumstance worthy of all attention, and admiration, that 

 the works of Nature even those apparently the most complicated 

 and elaborate are ever, when rightly understood, found to be per- 

 formed with extremely few materials, and by the simplest of all 

 possible processes. This truth is exemplified in the most interesting 

 manner, in the structure and economy of Plants. Infinite as are 

 the forms, and varied as is the texture, of the external organs of 

 plants, it has been satisfactorily shown, that all those protean 

 appendages are, in fact, nothing more than a series of successive 

 modifications (or metamorphoses, as they have been termed,) of that 

 tissue which, in the germinating seeds, appears in the condition of 

 crude cotyledons, and which in subsequent stages as the plants are 

 developed and matured is put forth in the more highly organized 

 State of stem leaves, floral leaves (or bracts], sepals, petals, stamens , 

 and pistils (or young fruit}. For an early, ample, and most interest- 

 ing exposition of this doctrine, we are indebted to the celebrated 



