444 



PHANEROGAMS. 



oflen periodically in terminal rosettes (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 Cycadese 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. \\\ Jimiperus co??imunis, indited, buds occur in most of .the 

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

 only in the axils of the scale-like lower 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 foHage-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 primary branch, 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. 

 IVIany Conifers exhibit a very regular arrangement of those branches of diflerent 

 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 pseudo-whorls of several 

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

 frequently repeated on the branches themselves {e.g. Pinus sylvestris^ Ai-aiicaria 

 brasiliensis, and especially PhyUodadus 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 (<?. 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 Libocedrus, 

 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 

 four orders of shoots are developed in one plane in such a manner that a system 

 of this kind assumes a definite contour and somewhat the appearance of a pinnate 

 leaf. In Taxodium the foliage-leaves are formed in two rows on slender branches 

 a few inches in length ; in T. distichiim these fall off in the autumn together with 



' In many species also of Abies and Pinus 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 comb-like rows. 



