xxiv INTRODUCTION TO BOTx\Ny. 



order Dice'cia, the different descriptions of flowers are, on two 

 separate plants. 



We have given a brief explanation of the Linnsean Classes 

 and Orders. We may next observe, that generic distinctions 

 are founded on the fructification, that is to say, the flower and 

 fruit. Hence plants agreeing in their parts of fructification, 

 are placed under one genus or kind; and all such plants as 

 differ in their parts of fructification are to be placed under 

 different genera, or kinds. The characteristic mark of each 

 genus is to be determined from the number, figure, propor- 

 tion, and situation of all the parts of fructification. We also 

 endeavour to fix upon some one single mark, that is constant 

 in the flower, and we make it the essential generic character; 

 for example, the pore in the claw of the petal in the genus 

 (ranunculus,) crovo-foot ; the singular construction of the petal- 

 form stigma, in the genus, iris. 



Specific differences in plants arise from any circumstance, in 

 which plants of the same genus are found to disagree; pro- 

 vided such circumstance be constant. Where plants agree in 

 certain peculiarities of flower and fruit, they are placed under 

 the same genus or kind, and have one common name, appli- 

 cable to all the species or sorts, contained under a genus or 

 kind ; for example, the term rosa, or rose, is given to all the 

 different sorts, or species of roses ; for example, the dog-rose, 

 (Rosa canina,) the briar-rose, (Rosa rubiginosa,) and so on; 

 the term I'ose is applied to all species, or sorts of rose. The 

 species, or different sorts of plants are distinguished by various 

 marks, for example, by differences in the root, trunk, leaves, 

 supports, (fulcra,) thorns, prickles, hracteas, stipulas, modes 

 of Jlowering, (inflorescence.) The parts o^ ihe Jlo'wer and 

 fruit, also furnish marks to distinguish one species from 

 another. 



The parts just mentioned upon which the specific dif- 

 ferences depend shall next be described in order. 



Parts on which Specific Differences chiefly 

 depend : viz. — 

 The Root, &c. The root may be spindle-shaped, (fusiform,) 



