THE ANGIOSPERAIAE 1073 



and Bentham and Hooker give an inclusive definition which combines both 

 the older and the newer, less abstract ideas: " The inflorescence of a plant 

 is the arrangement of the flowering branches and of the flowers upon them. 

 An inflorescence is a flowering branch or the flowering summit of a plant 

 above the last stem leaves, with its branches, bracts and flowers." The 

 latter sense is that in which the word is now usually understood. 



\'egetative branching is classified as monopodial or svmpodial (see 

 Volume I, p. 838), the former being considered the more primitive form. 

 Flowering branches show a similar distinction, the monopodial tvpes being 

 called racemose or indefinite and the svmpodial types called cymose or 

 definite. More or less parallel with this distinction there runs a further 

 difference, namely in the order of the opening of the flowers. In monopo- 

 dial types the flowers furthest from the apex usually open first and the order 

 of opening is therefore acropetal or centripetal, w hile in sympodial forms 

 the order is reversed, i.e., it is basipetal or centrifugal. This latter dis- 

 tinction is not however universally valid and the attempt to graft it on to the 

 simple monopodial-sympodial differentiation has been productive of much 

 confusion and has led to the condemnation of inflorescence classifications 

 in general as inconsistent and unsound. Xo such inconsistencv exists as 

 regards the mode of branching, and if we retain a clear idea of monopodial 

 and sympodial construction respectively, it will afford us the most useful 

 clue to the labyrinth of inflorescence types. 



The amount of distinction between flowering and vegetative branches 

 is variable. Some plants, e.g., Geranium, show little or none. In most 

 cases, however, there is a distinction of foliage, the leaves of the inflores- 

 cence branches being modified, often reduced, from the foliage form. They 

 are distinguished as bracts, while those on the flower stalk itself, when 

 present, are called bracteoles. They belong to the class of hypsophvlls 

 and they have been discussed in the chapter on leaves in Volume I. Extreme 

 differentiation of the inflorescence may lead to the complete suppression of 

 bracts and bracteoles, as in many Cruciferae, producing that rare pheno- 

 menon, a leafless stem. 



The inflorescence branches generally form the summit of the plant or at 

 least of the shoot systems in which they appear. Such inflorescences are 

 called terminal. A minority of inflorescences are, on the other hand, 

 intercalary, that is they occur as zones in the development of the shoot, 

 which continues its vegetative growth beyond them. Pseudo-terminal 

 inflorescences may develop from the intercalary type, as in some Wintera- 

 ceae, such as Driinys, by abortion of the terminal bud of the branch, so that 

 a group of axillary inflorescences becomes congested at the apex of the 

 branch. 



Intercalar\' inflorescences usually consist of sympodial, axillan.- shoots 

 on a monopodial vegetative axis. These may be either complex, many- 

 flowered cymes or single flowers in the leaf axils. Numerous transitional 

 types suggest that there has been evolution both by amplification and by 

 reduction. 



