INTRODUCTION. Xlll 



peculiar secretions being restricted or confined to certain por- 

 tions of the organism. 



The analogy between the vegetable and animal tissues is 

 beautifully apparent in the secretory action of the cells of pha- 

 nerogamous plants. The same endochrome, or coloring matter, 

 no longer gives an uniformity of hue to the tissues, but the 

 leaves which terminate the axis of growth become crowded 

 together into a beautiful rosette at its summit, and secrete a 

 variously colored endochrome, which has received the name of 

 chromule (^pw^ta color), in contradistinction to chlorophyl 

 j green, $Mkov leaf), which is the substance which gives 

 leaves their green hues. 



But the possession of a terminal rosette of beautifully 

 colored leaves, popularly called the flower, is by no means the 

 principal characteristic of Phanerogamous vegetation, since 

 in some flowering plants, as for instance in the grasses, these 

 colored investments become abortive and rudimentary. Yet 

 the organs essential to the formation of the embryo are there, 

 the stamens and pistils, and it is the presence of these bodies 

 which constitute the true flower. 



The difference between phanerogamous and cryptogamous 

 plants consists in the possession by the former of stamens and 

 pistils, or true flowers, (of which the latter are wholly deprived,) 

 by the mutual action of which an embryo or seed is produced, 

 which is a much more highly organized body than the spore. 

 The spore from which every cryptogam is developed is commonly 

 a simple cell filled with organic matter, and the organs which 

 it developes in germination form themselves as they appear ; 

 but in the embryo or seed, these organs existed before, and are 

 only increased by the act 'of germination. The character of an 

 embryo in organic beings is, that it contains, in a rudimentary 



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