BOTANY. 311 



formation each year of a new conical layer or enveloping mantle of 

 wood and bark, which extends from the top to the bottom of the tree. 

 The following law will express the relation subsisting between the two 

 dimensions of length and breadth : the branches are more cylindrical 

 the longer they are, and more conical in proportion as they are shorter. 



As examples of well-marked conical growths, we may mention those 

 extremely abbreviated shoots called thorns, of which the blackthorn 

 and the American cockspur thorn furnish us with good examples. 

 That thorns are only abortive shoots or branches, is proved by the wild 

 plum-tree ; this tree when planted in a good soil changes its thorns in- 

 to branches. 



In the case of the Weeping Willow, on the contrary we have an 

 instance of branches which tend more to a cylindrical than to a coni- 

 cal 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 picturesque of objects. 



But the conical growth of trees is sometimes strikingly apparent in 

 their landscape character, or general outline when viewed from a dis- 

 tance. This is the case in the great natural order Coniferce, or the 

 cone-bearing family. The trees belonging to this order, such as the 

 Juniper, the Red Cedar, the Norway Spruce Fir, and the celebrated 

 Norfolk Island Pine, when seen from a distance, are clearly conical in 

 their outline ; and this is the case with all the other members of this 

 family. The leaves of these trees are excessively narrow and small, 

 the blade being reduced to an abortive condition. They have been 

 called by the German botanists with some propriety needle-leaved 

 trees. These leaves are quite as capable of forming wood as those 

 which possess a true lamina or blade, for they make up by their im- 

 mense number and their persistent nature for their want of surface. 

 The branches of the fir and yew have always on them the foliage of 

 five or six summers, their leaves remaining usually that length of time 

 attached to them. 



The conical form is, in fact, more or less the original form of all 

 trees during the earlier portion of their life; for "at first, growth takes 

 place in the direction of the main stem," and the growth of the branch- 

 es is consequently greatly restricted ; but after a certain number of 

 years, the stem obtains its greatest height, and growth is " diverted to 

 its leading branches," which lose their conical figure or outline consid- 

 ered collectively, and, spreading out on all sides, form a dome-shaped 

 or hemispherical top or crown. This is particularly grand in the horse- 

 chestnut, the lime-tree, and the elm, which make for this reason a fine 

 appearance on a lawn or in a park, in addition to the recommendation 

 of the perfect shade which they afford. At this second stage in the 

 life of the tree, the main stem is no longer distinguishable from the 

 other branches, because they have made with it an equally powerful 

 growth. In the Coniferae, however, development is not carried so far, 

 for the tree stops at the first stage, and therefore retains permanently 

 its cone-like appearance. For this reason, as well as on account of 

 the simplicity of their leaves and flowers, and their high geological 

 antiquity, coniferous trees may be regarded as of a low type of organi- 

 zation. 



