126 DEVELOPMENT OF COMPOUND 



overshadow them. They differ, however, in one particular. 

 The first and subsequent generations of side shoots in trees 

 are formed in embryo the first year, enveloped beneath the 

 covering leaves of a winter's bud through the cold season, 

 and develop as shoots the second year ; but herbaceous plants 

 are without these covering leaves. They need them not, 

 because they develop all their branches in one season. This 

 activity of the ramifying process the first season undoubtedly 

 must tend to exhaust the vegetative powers of the herbaceous 

 axis, so that the period of puberty arrives in a few weeks or 

 months, and the plant flowers, forms its seed, and thus 

 rapidly passes through the same cycle of life-changes which, 

 in trees, it takes centuries to perfect and fulfill. 



We are now fairly in a position to show that leaf ramifica- 

 tion is governed by the same general laws as stem ramification. 

 Assuming that the midrib and petiole of the leaf, when it 

 possesses one, corresponds to the leading or primary axis of 

 the branch, then the first and most prominent sets of fibrous 

 fasciculi which separate themselves from the midrib will also 

 correspond with the powerful side axes of the first order in 

 the branch ; and where the fibrous portion of the leaf takes 

 a high degree 'of development, as is the case in compound 

 leaves, there is in the leaf precisely the same tendency to a 

 repetition of itself, on a smaller scale of architecture, as there 

 is in the branch, and one or more generations of leaflets will 

 be formed, whose fibrous ramifications, like those of successive 

 generations of branchlets, are more and more retarded, until 

 finally the vegetative powers of both leaf and branch are 

 reduced to zero. 



Again, the stem and branches of the tree are all conically 

 constructed, tapering toward their extremities. In like man- 

 ner, the bundles of fibre which ramify through the green bark 

 or parenchyma of leaves are equally tapering. The midrib 

 or main fasciculus of fibres decreases in diameter from the 

 base to the apex of the leaf, as the enveloping layers of fibre 

 separate from each other. In such leaves as those of the 

 Chestnut, all further ramification is at once stopped by the 

 anastomosis of the fibres amongst themselves, the parenchy 



