128 DEVELOPMENT OF COMPOUND 



paniculata, a beautiful Chinese shrub, cultivated in sheltered 

 situations, for the sake of its elegant leaves and panicles of 

 yellow flowers. In the leaves of this plant, the different stages 

 in the process of new leaflet-formation may be traced at a 

 glance. There is apparent that retarded development of the 

 leaf ramifications in the first, second, and third generations of 

 forming leaflets (Figs. 1, 2, 3), which spring from the primary 

 axis or costa3 of the leaf; it will also be perceived that the out- 

 line figure of the side leaflets corresponds to that of the primary 

 or parent leaf, from which they differ only in size, being only 

 a repetition of the parent leaf on a smaller scale. Thus the 

 lateral fibres given off from the primary costa or main folia- 

 ceous axis of the leaf, gradually decrease in size from the 

 middle to the apex and base of the leaf; it is the same with 

 the fibrous bundles given off from the secondary costae : these 

 are the most developed toward the middle of each leaflet ; 

 hence, toward their summits, the leaflets of the second genera- 

 tion are still in a state of anastomosis, or only partially formed. 

 The lowest leaflets of this generation are the most completely 

 developed ; but they are sessile, their petiole is rudimentary, 

 and the vegetative power is so enfeebled in the upper leaflets, 

 that the parenchyma is increasingly decurrent along the line 

 of the costae. These lower lateral leaflets are therefore clearly 

 only the secondary leaflets arrested at a still lower stage of 

 their development. If we examine them carefully, we shall 

 find that the lateral fibres proceeding from their costse or 

 midribs produce the sharp incisions of their margin. These 

 sharp points are therefore the tops of the new leaflets of the 

 third generation, and by consequence the last expiring efforts 

 at new leaflet-formation. The marginal development of new 

 leaflets, like the lateral development of new branchlets, is 

 here reduced to a minimum, being arrested in its first stages. 

 There is a Comparative Anatomy of Plants as well as of 

 Animals, which has yet been only indifferently studied. More 

 careful researches are necessary in this interesting field. The 

 gradual simplification of leaf-structure in the neighborhood 

 of the flower, the result of a loss of vegetative energy in the 

 leaf, and the antagonism of reproduction, is a fact in Vegetable 



