108 AN INTRODUCTION 



In some genera one part of the fructification is 

 found to be the most constant, and in others another ; 

 but there is no part that is not liable sometimes to a 

 variation : thus we find the Pericarpium variable in 

 Impatiens, Campanula, Primula, Papaver, Cistus, 

 Fumaria and Arbutus ; the calyx in Nymphaea, and 

 Cornus ;' the corolla in Vaccinium, Convallaria, An- 

 dromeda, Gentiana and Linum ; and the seeds in 

 Ranunculus and Alisma. 



If the flowers agree, but the fruits differ, the genus 

 Ought not to be parted : thus in those extensive ge- 

 nera, the Cassia, Hedysarum, Sophora, Lavatera, 

 Hibiscus, and Mimosa, so great a number of species 

 have been ranged under the same genus, on ac- 

 count of the conformity in the flowers, though there 

 is a variation in the fruit. 



That the figure of the flowers is more certain 

 than that of the fruit appears from many examples ; 

 as from Campanula, Primula, Antirrhinum, Alisma, 

 Hibiscus, Cistus, &c. but the proportion of the parts 

 is subject to very great variation. 



The number of the parts is more liable to variation 

 than their figure, and is found sometimes to vary 

 even upon the same plant ; as in Ruta, Chrysospleni- 

 um, Monotropa, Tetragonia, Euonymus, Philadel- 

 phus, and Adoxa ; in the flowers of all which the 

 number of the parts varies from five to four : In these 

 doubtful cases, the natural number must be collect- 

 ed from the primary flower ; but in the variations of 

 the number of the parts, there is a proportionable 

 affinity worth remarking. In flowers, the stamina 

 usually vary from ten to eight, and from five to four ; 

 the corolla and calyx from five to four, and the whole 

 flower from four to three ; and the fruit also usually 

 varies from five to three, and from five to four. 



The situation of the parts is the most constant, 

 very rarely varying in the same genus. 



