214 MORPHOLOGY. 



region where new cells are also formed, but so that the new ones 

 are partly pushed outwards and partly persist as formative cells in 

 the vicinity of the stem. In this way a mass of cellular tissue is ex- 

 panded out in the form of a lamina from this region of the stem, ap- 

 pearing either as an undivided organ continuous in its whole circuit 

 at the base, or, divided from the very bottom into two or more 

 portions, it presents itself under the form of two or more organs 

 all situated in the same plane. Through the accumulation of cells 

 upon the elongating apex, the lateral region just described is re- 

 moved continually further from the peculiar throng of active cell- 

 formation ; perhaps it is on this account that its formative power is 

 exhausted after a certain time. The further enlargement of its 

 organs depends then solely on the expansion of cells already formed, 

 but this also has its limits. Thus, we find here two essentially 

 different form-producing processes, and we call their products ele- 

 mentary organs of the plant : Stem (caulis, sensu stricto) the pro- 

 duct of the first, formative force originally acting continuously 

 and unlimitedly in one direction ; Leaf (folium) the product of 

 the second, dependent force, which defines its own boundaries in 

 the manner peculiar to it. The first leaf or first leaves are called 

 cotyledons. If we refer the term to a line * drawn from the root- 

 end through the middle of the embryo to the stem-end, which 

 then answers at once to the direction of development both of root- 

 let and stem, the stem is called an axial structure (axis), the 

 leaves lateral organs (paries laterales, appendiculares). In most 

 cases, some more succeeding leaves, besides the cotyledons, are 

 formed on the embryo ; these, with the rudimentary stem on which 

 they are borne, are called the plumule (plumula). Then ensues 

 a pause in the formative activity, the embryo is finished, the seed 

 (the seed-bud surrounding it) is ripe. 



In all common plants the root, stem, and leaves are so conspicuous, 

 that their distinction in language is much older than any trace of a 

 scientific contemplation of plants. At the same time, nothing has so 

 entangled science, for a long time deprived it of all secure foundations, 

 as those very three organs ; and for this reason : that men were contented 

 to transfer these into science as they were intuitively understood in 

 common life, and neglected to transform the obscure notions of the 

 sensuous perception, which vary with the mode in which an impression 

 is received in every individual, and are, therefore, wholly incommuni- 

 cable, into a clear definite conception framed from their characteristics, 

 and therefore universally communicable. DeCandolle begins : " Les 

 feuilles sont, COMME CHACUN SAIT, les expansions ordinairement planes" 

 &c. What, then, is a science for, if it brings us nothing more than what 

 every one knows without it ? One cannot dispute at all with most bo- 

 tanists whether anything is a leaf or not, because they do not seek in 

 any way to explain in what its characteristics are to consist, as, for in- 

 stance, Agardh, DeCandolle, Link, and others. The greater portion 

 throw in some character or other, which the most superficial knowledge 



* Which may also be a curved line, from the action of external influences. 



