A NGIOSPER MS . C22 



cations (as in some species of Silene) ; a dichasium may bear capitula (e. g. Silphium), 

 or even in its first branches or in those of a higher order may pass into a helicoid 

 or scorpioid cyme (as in Caryophylleae, Malvaceae, Solanaceae, Linacese, Cynanchum, 

 Gagea, Heinerocallis, &c.). The mode of branching of the inflorescence is in most 

 cases different from that of the vegetative stem. Not unfrequently it passes abruptly 

 from one to the other, but often through intermediate modes of branching. 



In the older systems of nomenclature a number of other terms are given to various 

 forms of inflorescence, such as glomerulus, corymb, &c. ; but they all designate merely 

 the habit or external form of the system, and must be referred, in a scientific description, 

 to one or other of the above forms or to combinations of them. 



Number and Relati've Position of the Parts of the Flonver. Just as the forms of branch- 

 ing of the inflorescence are usually difl'erent from those of the vegetative stem, the 

 arrangement of the leaves of Angiosperms is also usually diflTerent on the shoot which 

 constitutes the flower from that on other parts of the same plant. The cessation of 

 the apical growth of the receptacle, its great increase in breadth, or even hollowing out, 

 before and during the time when the perianth and the sexual organs are being formed, 

 influences their order of succession and their divergence from one another. But since, 

 notwithstanding the extraordinary variation of the other relations of form, the true 

 position of the floral leaves varies but little — though it may often be diflicult to determine 

 — the knowledge of this position is often of great importance in the determination of the 

 affinities of the species, and hence for purposes of classification. This is especially 

 the case if we at the same time take into account the abortion of individual members 

 which is here of so common occurrence, the multiplication of the parts which take place 

 under certain circumstances, and their branching and cohesion. 



In order to facilitate a description of these relationships, it is necessary to explain 

 certain terms and methods of description. 



In the first place it is important to denote the position of all the parts of a flower 

 with respect to the mother-axis of the floral shoot. For this purpose the side of the 

 flower which faces the mother-axis is termed the posterior, that which is most remote 

 from it the anterior side. If a plane be imagined to divide the flower longitudinally from 

 front to back, and to include the primary axis of the flower as well as that of the 

 mother-shoot, this is the median plane of the flower, dividing it into a right and a left 

 half. Floral leaves, as well as ovules and placentae which are bisected longitudinally 

 by the median plane are said to have a median position, either posterior or anterior. 

 If another plane is now imagined at right angles to the first, and also including the axis 

 of the flower, it may be termed the lateral plane ; this plane divides the flower into a 

 posterior and an anterior half, and parts which are longitudinally bisected by it are 

 precisely lateral. The two planes which bisect the right angle between the median 

 and the lateral planes may be called diagonal planes, and the parts which are bisected by 

 them be said to have a diagonal position. Flowers usually have some of their floral 

 organs placed exactly posteriorly or anteriorly, not so commonly exactly right and 

 left or exactly diagonally ; but usually other additional terms must be used, such as 

 obliquely posterior or obliquely anterior. 



If next the position of the parts of the flower with respect to one another be ex- 

 amined, their arrangement, as has already been mentioned, is either spiral or -verticillate. 



Flowers with a spiral arrangement of their parts are comparatively rare, and appar- 

 ently occur only in certain orders of Dicotyledons (Ranunculaceae, Nymphaeace^, Mag- 

 noliacex, and Galycanthacex). Braun has termed such flowers acyclic, when the tran- 

 sition from one foliar structure to another, as from calyx to corolla or from corolla to 

 stamens, does not coincide with a definite number of turns of the spiral (as Nymphaeaceae 

 and Helleborus odorus) ; hemicyclic when it does so coincide. This latter term may also 

 be employed when some of the foliar structures are actually cyclic (verticillate) others 

 spiral, as in Ranunculus, where the calyx and corolla form two alternating whorls, 

 followed by the stamens and carpels arranged spirally. Parts which have a spiral 



