CONIFERM. 



509 



summit, becoming thickened to a corresponding extent by the activity of a cambium- 

 ring, and thus becomes a slender cone attaining a height of 100, 200, or even 

 more feet ^, and a diameter at the base of 2 or 3 or as much as 20 feet. On this 

 highly-developed primary axis the lateral axes of the first order are produced; 

 often periodically in rosettes at the apex (pseudo-whorls) or distributed irregularly 

 and branching again in the same manner. Each primary axis usually grows more 

 vigorously than its secondary axes; and hence the collective form of the system of 

 branching, as long as the primary axis continues to grow vigorously, is that of a 

 panicle of conical or pyramidal form. While in Cycadeae the branching is almost 

 entirely suppressed, the peculiar form and beauty of Conifers depends chiefly on the 

 branching, the more so as the leaves are almost always small and inconspicuous, 

 serving only, as far as the outward appearance of the plant is concerned, as a cloth- 

 ing to the system of branching. The branching is always axillary ; but Conifers 

 differ from Angiosperms in not producing buds in nearly all the leaf-axils; in 

 Araucaria and some species of Taxus, Abies, and other genera, it is chiefly or 

 exclusively the youngest leaf-axils of a year's growth which produce branches, and 

 these grow vigorously. In Juniperus communis, indeed, buds occur in most of the 

 leaf-axils, but only a few develope. In Pinus sylvestris and its allies shoots are formed 

 only in the axils of the cataphyllary leaves which are borne exclusively by the 

 primary stem and the permanent woody branches, remaining however very short, 

 and producing two, three, or more acicular foliage-leaves, from the axils of which no 

 lateral shoots are produced. In Larix, Cedrus, and Salisburia, buds are formed in 

 the axils of a considerable number — but not nearly all — of the foliage-leaves, a few 

 growing rapidly, and serving for the development of the branch-system, while others 

 remain very short, and form annually a new rosette of leaves without lateral buds. In 

 Thuja and Cupressus also, which are distinguished by their copious branching, the 

 number of small leaves is still very much larger than that of the axillary shoots. 

 Many Conifers exhibit a very regular arrangement of those branches of different 

 orders which arrive at their full development, the symmetry of the whole tree being 

 at the same time increased by their difference in size. The branches of the first 

 order on the upright primary stem are frequently formed in a pseudo-whorl of several 

 members at the conclusion of each period of vegetation, the same process being 

 frequently repeated on the branches themselves {e.g. Pi?ius sylvestris, Araucaria 

 hrasiliensis, and especially Phyllocladus trichomanoides, and many others) ; more 

 commonly a tendency to bilateral ramification appears on the horizontal branches 

 of the first order (as in Abies pectinata); and not unfrequently besides these strong 

 branches from which the framework of the tree is constructed, smaller ones are 

 also formed between them (e.g. in Abies excelsd). In many cases the arrangement 

 and growth of the branches are more irregular; the greatest deviation from this 

 type being shown in the Cupressinese, especially Cupressus, Thuja, and Lihocedrus, 

 in which the tendency to bilateral ramification ^ is seen even on the primary stem, 

 which is more perfectly developed on the lateral shoots. Branch-systems of three or 



' [The trunk o{ Sequoia {Wellingtonia) gigantea of California attains the height of 400 feet.] 

 * In many species also oi Abies and Piniis there is an evident tendency to bilateral development 



in the horizontal lateral shoots, the spirally arranged leaves inclining over to the right and left, and 



thus forming two omb-like rows. 



