406 FOURTH GROUP. — SEED-PLANTS. 



the distinctive name of hypsophyllary leai'es or bracts, and in this term are included 

 also the small leaflets {bracieoles) which grow on the flower-stalks and often have no 

 shoots springing from their axils ; sometimes leaves of this kind are entirely wanting 

 within the inflorescence or wanting at certain parts of it, and in that case the axes of the 

 flowers or their parent-axes are not axillary (Aroideae, Cruciferae, and many others). 

 The combination of these and other peculiar characters in various ways gives rise to 

 a very great variety in the forms of inflorescences, each of which is constant in a par- 

 ticular species, and is often characteristic of a whole genus or family ; the form of the 

 inflorescence is often decisive of the habit of the plant and has also a systematic 

 value. 



It will be found that the most satisfactory classification of inflorescences is one that 

 is founded chiefly on their mode of branching, because this is less variable than any 

 other character and can be referred to a few types ; it supplies also distinguishing 

 marks for the primary groups, which will then fall readily into subdivisions according 

 to the length and thickness of the different axes and other marks. 



The branching of inflorescences is here as everywhere either radial or dorsiventraP . 

 Dorsiventral inflorescences are those in which the axis of the inflorescence is 

 not, like a radial inflorescence, developed uniformly in every direction but is 

 seen to have two distinct sides, one of which (the side towards the primary 

 axis in lateral shoots) is termed the dorsal side, while the side opposite to it is the 

 ventral side. The two sides of the axis, which separate the dorsal and ventral sides, 

 are the lateral faces or flanks. A chief mark of distinction between the dorsal and 

 ventral sides is that one only bears flowers. The distinction is seen in a very 

 striking manner in many papilionaceous inflorescences, as in Vicia Cracca, in Urtica 

 dioica, and in the Boragineae, etc. Botanists generally have hitherto misunderstood this 

 peculiarity or have attempted to refer it to irregular growth and displacement ; but the 

 history of development and a comparison with other dorsiventrally branched parts of 

 plants show that these explanations are inadmissible. Intermediate forms are not 

 wanting between the two modes of branching, being found, for example, in the in- 

 florescence of the Gramineae. We will first consider radial inflorescences and proceed 

 further on to the dorsiventral, observing only here that the branching of dorsiventral 

 inflorescences is often extra-axillary, as will be shown more at length below. 



The first point to observe is, that every inflorescence originates in the normal ter- 

 minal branching of growing axes ; this branching in Angiosperms, with the exception of 

 the cases mentioned in section 14, is monopodial, that is, the branches arise laterally 

 beneath the apex of the growing mother-shoot; if leaves (bracts) are distinctly 

 developed on the latter, the lateral branches grow from their axils ; if they are indistinct 

 or abortive, the axes of the inflorescence are not indeed axillary, but their branching 

 and other conditions of growth remain the same as if there were bracts present, and we 

 need not lay any particular stress on this circumstance in determining the subdivisions. 

 The presence of bracts is of practical importance, because it makes it more easy to 

 perceive the true character of the branching even in fully developed inflorescences, the 

 axillary shoot being always lateral ; without this mark it is often difficult to say, in 

 the mature state of the inflorescence, which is a parent-axis and which a lateral, for the 

 latter often grows as vigorously or much more vigorously than the former. Of the 

 many individual forms of inflorescence we shall here give only the more common 

 ones, and without special regard to the question of symmetrical relationships within 

 themselves^. 



' Goebel, Ueber d. V^erzweigung dorsiventraler Sprosse (Arbeiten a. d. bot. Inst, in Wiirzburg, 

 II. Bd. 3 Heft. 



^ Compare the dissimilar descriptions in Ascherson's Flora der Provinz Brandenburg (Berlin, 

 1864) and Hofmeister's Allgemeine Morphologic, sec. 7. [See also the remarks of Asa Gray 

 in his Structural Botany, 1S80, and the grouping of inflorescences given by Dickson in Balfour's Class- 

 Book of Botany, 1871.] 



