THE CONICAL GROWTH OP TREES. 61 



In the case of {Salix Babylonica) the Weeping Willow, on 

 the contrary, we have an instance of branches which tend 

 more to a cylindrical than to a conical form. In consequence 

 of this peculiarity, the branches of this tree are long and 

 pendulous, their waterfall-like curvature is extremely 

 graceful, and, as they wave backward and forward in the 

 wind, the tree presents one of the most beautiful and pic- 

 turesque of objects. 



But the conibal growth of trees is sometimes strikingly ap- 

 parent in their landscape character, or general outline when 

 viewed from a distance. This is the case in the great IsTatural 

 Order, Coniferse. The trees belonging to this order such as 

 {Juniperus communis) the common Juniper, (Juniperus Vir- 

 giniana) the Red Cedar, and the different species of Fir and 

 Pine, when seen from a distance, are clearly conical in their 

 outline. This, in fact, is more or less the original form of all 

 trees in the first stages of their development. For, at first, 

 growth takes place principally in the direction of the leading 

 axis or stem, and the growth of the branches is consequently 

 greatly restricted ; but after a certain number of years, the 

 stem obtains its maximum elevation, and growth is diverted 

 to the branches. The tree then loses its conical form and 

 begins to spread out on all sides, forming, as in the case of 

 the Linden and Elm, a magnificent dome or crown. In the 

 Coniferse, however, development is not carried so far, and 

 the tree still retains its cone-like appearance through all 

 the stages of its life. For this reason, as well on account 

 of the simplicity of their flowers, these trees may be con- 

 sidered of a low order of organization. 



The leaves of the tree are the true sources whence pro- 

 ceeds the elaborated formative material used in the building 

 up of its stem and branches. 'Now, this law is plainly ap- 

 parent in the single axis, the structure of which depends 

 on the manner in which the phytons are superposed and 

 combined, and in the peculiar arrangement of the vascular 

 bundles below them. The phytons which produce the 

 single axis are arranged spirally around the axis in accord- 

 ance with laws peculiar to each species. 



This spiral disposition of the leaves is a provision for se- 



