176 MORPHOLOGY OF MEMBERS. 



the latter ; in this manner is formed the bract on the flower-bud in Anthemis, Sisymbrium^ 

 and Umbellifcrai. When in addition to this it also happens that after the formation of 

 the subtending leaf the basal portion common to it and to the bud lengthens, then the 

 former is elevated on the axis of its axillary shoot, and the shoot appears to have no 

 subtending leaf, because this latter is placed upon it, and constitutes its first leaf. This 

 occurs in Tbesium ebracteatum, Samolus Falerandi, Spireea, Ruta, Tilia (in this case the 

 bract and the entire inflorescence), Borragineae, Solanaceae, and Crassulaceae ^. 



(y) In reference to the relative time of production of the leaves and lateral branches 

 on a primary axis, the general rule is that axillary buds are formed later than their 

 subtending leaves. This is the case in Gharaceae, Hepaticae, Equisetaceae, and, with the 

 exception of some inflorescences, in Phanerogams. In the region of growth the sub- 

 tending leaf attains a considerable size, even in the latter, before its axillary shoot is 

 formed ; and in the meantime new and younger leaves are produced above the youngest 

 bud. In those inflorescences, on the contrary, where the formation of leaves is more or 

 less suppressed, the bud is often formed immediately after the bract, or at the same time, 

 or even earlier than it ; and in the two last cases the bract has often the appearance of 

 being a product of the bud (see conclusion of par. /3). It may even happen that when 

 the flower-buds are formed very rapidly, the production of bracts is altogether sup- 

 pressed, as in most Gruciferae (Fig. 132)^. 



(b) The fact that lateral shoots arise far most frequently at a greater distance from 

 the apex of the stem than the youngest leaves, distinguishes them sufficiently from 

 dichotomous branchings, which must always of necessity arise above the youngest leaf. 

 But even when the leaves are visible only later than the corresponding buds, as in the 

 inflorescence of Grasses, or is even completely suppressed, as in most Gruciferae, it is 

 still impossible to confound lateral with dichotomous branching, if, as in these cases, the 

 cone of growth greatly overtops the youngest lateral bud, and continues to grow in a 

 straight line (P'igs. 117, 119, pp. 154, 155). Still more conspicuous is the distinction 

 between lateral branching and dichotomy when the primary axis ends in a broad flat 

 apical surface, as in the young capitula of Compositae. Here the lateral shoots (the 

 flowers) are so small in comparison to the mother-shoot, and are from the first placed at 

 so great a distance from its apex, and so uniformly on all sides of it, that the mother- 

 shoot must be regarded as the independent centre of all new formations. The idea 

 of dichotomy supposes, on the contrary, that the mother-shoot ceases as such, and that 

 two branches, at first at least equally strong, continue to grow in length in diverging 

 directions in its place. 



If it is desired to include lateral branching from the growing point and dichotomy of 

 the apex under one common term, in order to distinguish them from the adventitious 

 formation of branches from older portions of the stem, leaves, or roots, the expression 

 terminal Branching commends itself. 



Sect. 25. Different capacity for Development of the members of a 

 Branch-system^. — Systems of similar members originate by branching; out of 

 a root a root-system originates, out of a shoot a shoot-system ; when a leaf 

 branches, we get a pinnate, digitate, lobed, or incised leaf, &c. We may therefore 

 examine the more important relationships of form of such a system, taking into 

 account for the time only the relative size and capacity for development of the 



^ See Warming, Recherches sur la ramification des Phanerogames. Copenhagen 1872, p. xx. 



2 [On the suppression of the bracts in Gruciferae, see Masters, Journ. Linn. Soc. 1875, vol. 

 XIV. p. 39I-] 



3 Nageli und Schwendener, Das Mikroskop, p. 599. — Hofmeister, Allgemeine Morphologic der 

 Gewebe, Sect. 7. — Kaufmann, Bot. Zeitg. 1869, p. 886. — Kraus, Medic.-Phys. Soc. in Erlangen, Dec. 

 5, 1870. — Warming, /. c. 



