THE INNER ORGANIZATION OF TREES. 51 



punctum vegetationis or growing point of the young shoots 

 through winter ; they die and fall off in spring. "When the 

 new generation of phytons are put forth into the atmosphere, 

 another series of covering-leaves are formed by them, which 

 are left in charge of the growing points of the shoot through 

 winter, as before. In this manner -there is an oscillation 

 between these two kinds of leaves in trees for a series of 

 years, until the tree arrives at an adult state. The different 

 phytons of the flower designated by botanists as sepals, pe- 

 tals, stamens, and pistils, whose individuality is so strikingly 

 marked, then make their appearance, and these die in suc- 

 cession in developing the walls of the pericarp, or seed- 

 vessel. Lastly, the vitality of the walls of the pericarp 

 itself is exhausted ; for the whole of the nutritious contents 

 of its cells must pass through the funiculus, or vegetable 

 umbilicus, the little stalk by which the seed is fastened to 

 the seed-vessel, into the nursing-leaves and seed-covers, 

 before the germ of the future plant can be fully formed. 



There can, therefore, no longer remain a particle of 

 doubt about the fact that the cells which form the organ 

 of a tree, work together in communities according to fixed 

 laws of succession, and that the design of the whole of these 

 arrangements is to effect such changes in the sap as to secure 

 its final transmutation into those peculiar products by which 

 the tree is distinguished. Just as in civilized communities 

 the raw material of our manufactures goes through a regular 

 series of changes in the hands of a great number of work- 

 men, before the goods are manufactured and fit for sale, so 

 with the ultimate products of plants, which are as various 

 as the plants which produce them. These have all been 

 manufactured from the raw material, or sap, which has gone 

 through a regular series of preparatory metamorphoses, or 

 changes in the interior of the plant. The lowest order of 

 individuals employed in effecting these changes are the cells, 

 which combined together into communities form those dif- 

 ferent varieties of phytons which develope about the axis 

 or stem of the plant. These phytons or cell-communities 

 constitute a still higher type of individuals, which appear 



