RELATION OF aUANTITY TO ESTHETIC SENTIMENT. 411 



In the acotyledons, or acrogenous classes of plants, two is tlie 

 typical number. In lichens, ferns, and the like, two and its multiples 

 prevail. Thus in the order Equisetacese, the branches, sheaths, and 

 furrows are found in the numbers 2, 4, 8, &c. ; and this is still more 

 -remarkable in the crowded teeth which fill the sheaths, and which are 

 always found in multiples of two. So also in the order of mosses, we 

 have teeth in the following numbers, 4, 8, 16, 32, and, in one in- 

 stance (polytrichum), we have 64, 



In the next class, the monocotyledons, as seeds, grasses, and other 

 seed-bearing plants, we find three to be the prevailing number. That 

 three and its multiples here prevail, is sufficiently illustrated by the 

 use of such terms as Tricandria, Trigynia, Hexandria, &c., in de- 

 scribing the different orders of plants in this class. 



In the diocotyledons, or highest order of plants, we have Jive as the 

 typical number. Of this class the oak, with its acorn, may be taken 

 as the great British type. Here may be observed five leaflets on a 

 common stalk : the flower stem has five primary branches ; these in 

 turn have five secondary ; and so repeatedly. The articulated leaves 

 of this order are divided into five parts, and the stamens are in 

 multiples of five. 



Seven is found only in the class Heptandria, of which the horse- 

 chestnut may be taken as the example. In the British Flora, there 

 is only one plant belonging to this class — the Trientalis Europea, or 

 chick-weed (winter-green.) But this number, so rarely found in the 

 vegetable kingdom, is the great typical number in other departments 

 of nature. 



We find a numerical relation of a deeply interesting kind running 

 through the various parts of the plant. This relation is most ap- 

 parent when we examine the various parts of a complete flower. Thus 

 in the flower of the monocotyledon, where three is the prevailing 

 number ; in it the outer row represents the calyx, with three sepals ; 

 the second row the corolla, with three petals ; the third row repre- 

 sents the stamens, of which there are six — two rows of three each ; 

 and in the centre there are three pistils united in one. So also in the 

 flower of the diocotyledon we have in the outer row five sepals ; in 

 the second, five petals ; in the third, five stamens ; and in the centre, 

 five pistils. 



If we compare the structure of the whole plant with that of the 

 leaf, we find a striking correspondence both as to disposition and 



